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2014 NIGMS Cell Day Online Chatroom Transcript

Cell Day 2014

The 2014 NIGMS Cell Day chat was held on Friday, February 28, 2014 from 10 a.m. to 3 p.m. EDT. Scientists from across the Institute answered questions from students, teachers and the general public.

Please take a moment to give us some feedback about Cell Day 2014 and the online chat. Any information you provide will help NIGMS improve future Cell Days.

Information - Moderator Moderator: Welcome to Cell Day! The chatroom is now open, and we're excited to see so many questions already.

If an organism dies, do all of its cells immediately die too?
Darren Sledjeski, Ph.D.: No. It would take some time for all of an organisms cells to die. But, if you also consider the microbes that live in and on our bodies as part of "us" then they might not die and could exist in the environment indefinitely.
Southeastern Greene School District in PA (11th grade student)

What is Somatic cell nuclear transfer?
Alexandra Ainsztein, Ph.D.:  In genetics and developmental biology, somatic-cell nuclear transfer is a laboratory technique for creating a clone embryo with a donor somatic nucleus. The nucleus is removed from one cell and then put into another cell where the nucleus was previously removed.
Southeastern Greene School District in PA (11th grade student)

Do cells have protective factors?
Jessica Faupel-Badger, Ph.D.:  Yes, cells have many protective factors. For example, there are regulators of the cell cycle to make sure cells divide only when given the appropriate cues. Scientists working in this area have even received the Nobel Prize!
Southeastern Greene School District in PA (12th grade student)

What combination of molecules confers differentiation to specific cell types?
Darren Sledjeski, Ph.D.:  That is a simple question that has a very complex answer. There are many many types of molecules, proteins, RNAs etc that determine how cells differentiate. It is a complex question that we do not have a complete answer to. In fact determining how cells differentiate is an active area of research supported by NIGMS.
Southeastern Greene School District in PA (11th grade student)

Are there other uses of stem cells besides using them to treat disease?
Darren Sledjeski, Ph.D.:  Good question. Stem cells are valuable for research too. They can tell us a lot about the basic mechanisms of life. Stem cells could also be used for testing new medical treatments or even as diagnostics.
Southeastern Greene School District in PA (11th grade student)

If DNA makes up cells, than what makes up DNA and proteins and all the little things that make up that makes up everything else
Ward Smith, Ph.D.:  Atoms make up molecules. DNA is made of C,N,O,P and H. The molecules in DNA are nucleic acids made of sugar, phosphates, and base molecules.
Webutuck High School in NY (9th grade student)

When will stem cell research lead to new disease cures?
Jessica Faupel-Badger, Ph.D.:  This is a terrific question! Stem cell research holds great promise. To date, there are clinical trials with human patients focused on examining the use of stem cells to treat neurologic diseases and diabetes. A good resource for more information is the following NIH website: http://stemcells.nih.gov/info/pages/health.aspx
Southeastern Greene School District in PA (11th grade student)

How can you get stem cells other than your umbilical cord?
Donna Krasnewich, M.D., Ph.D.:  Actually there are stem cells in most of the organs of our body. Remember these are cells that have the potential to become "differentiated" or mature to have characteristics like the cells in that organ. An example of another common source of stem cells is from bone marrow, where cells are harvested typically from the hip bone of an adult. These cells have been used in many experiments to help us understand how cells differentiate, or gain specific functions and shape. For more information on stem cells try this link: http://stemcells.nih.gov/info/basics/Pages/Default.aspx. Thanks for the great question, there is so much great science ahead!
Southeastern Greene School District in PA (11th grade student)

How long do cells live?
Alexandra Ainsztein, Ph.D.:  Good question. This will depend on the type of cell and the health of the cell. Cells go through cycles of cell growth and division and then may cycle into the apoptosis (or cell death) if cell cycle checkpoints are triggered. The shortening length of the telomeres of the chromosomes is another factor that could shorten the cell life.
Southeastern Greene School District in PA (11th grade student)

Is tissue engineering a technology that can help nerve cells grow back?
Brian Pike, Ph.D.:  Hello Pennsylvania! Thanks for submitting your question. The short answer is yes, tissue engineering can be used to grow nerve cells and this is area of active research. Nerve grafts are one way that tissue engineering can be employed to grow nerve cells and tissues. Nerve grafts contain aligned tissue structures and Schwann cells that support and guide neuron growth through a damaged area, and this can encourage function of the tissue to be restored. Now medical researchers have developed a way to manufacture artificial nerve tissue with the potential to be used as an alternative to nerve grafts. Much more research needs to be done in this area to make this useful in humans, but the future looks bright.
Southeastern Greene School District in PA (11th grade student)

How does rna make proteins?
Jon R. Lorsch, Ph.D.:  Great question! Cells have machines in them called ribosomes, which are actually made of both RNA and proteins. Ribosomes grab onto messenger RNA molecules floating around in the cytoplasm of a cell and read ("translate") them into the proteins that they encode. The sequence of RNA bases is what determines what protein each messenger RNA encodes. Another kind of RNA molecule called transfer RNAs have the amino acid building blocks of proteins attached to them and the ribosome uses these transfer RNAs to build up proteins as they read a messenger RNA. The inside of a cell is basically like a factory full of machines reading messenger RNAs to make proteins in a process very much like an assembly line. Cool, right?
Webutuck High School in NY (9th grade student)

How do we stop bacterial infections that can not be controlled with antibiotics?
Darren Sledjeski, Ph.D.:  Good question with a scary answer. In fact, we can't. Without antibiotics we would have to depend on our own immune system to clear a bacterial infection. Physicians can provide supportive care but we have no other good way of treating the infection. That is why the rise of antibiotic resistant bacterial pathogens is such a concern.
Southeastern Greene School District in PA (12th grade student)

Can stem cells therapy cause cancer?
Jessica Faupel-Badger, Ph.D.:  Good question! A primary focus of using stem cells in therapy is to find a way to make the stem cell differentiate into the needed cell type for the given disease or condition. It is highly unlikely these differentiated cells would lead to cancer.
Southeastern Greene School District in PA (11th grade student)

What holds cells together?
Alexandra Ainsztein, Ph.D.:  Many cells - especially epithelial cells, which are found in a sheet, have intracellular junctions called "tight junctions", which are proteins found in the cell membranes around the edges of the cell that bond tightly to the proteins of neighboring cells. Other cells, that have less strong (or less permanent) adhesions to each other - like a white blood cell crawling over the epithelium of a blood vessel - use different proteins and different adhesion types.
Southeastern Greene School District in PA (12th grade student)

Have any studies been done to show stem cells help cure cancer?
Jessica Faupel-Badger, Ph.D.:  This is a great question and very similar to question #10. Please see this answer.
Southeastern Greene School District in PA (12th grade student)

How do plants/animal cells differ in protein structure differ on the external structures?
Ward Smith, Ph.D.:  Proteins are very similar in both plants and animals. That is why we can learn the answers to fundamental questions in plants that can apply to animals as well. The type of of proteins will differ i.e cell wall protein in plants but there are many similarities
Southeastern Greene School District in PA (12th grade student)

How do the saved umbilical cords help provide stem cells and help research on it? Are there any laws regulating this?
Joe Gindhart, Ph.D.:  That is a great question. Stem cells from umbilical cord blood are genetically identical to the baby who donated it. Later in life, the donor might need those cells for treatment of certain diseases, such as leukemia, without having to worry about whether the donor cells are compatible with the patient. There are informed consent laws that regulate whether researchers can know the identity of the donor, as well as laws that ensure the proper storage and use of umbilical cord blood.
Southeastern Greene School District in PA (12th grade student)

Can embryonic stem cell lines come from aborted fetuses
Donna Krasnewich, M.D., Ph.D.:  Embryonic stem cells are cells that have not differentiated, or developed characteristics of other cells. A fetus already has differentiated cells that are past the developmental stage and are no longer considered embryonic cells. Thank you for this thoughtful question.
Southeastern Greene School District in PA (11th grade student)

Why are some staph infections so dangerous while others can just live on your skin ? I had pyomyositis and doctors were concerned that if might affect my heart.
Darren Sledjeski, Ph.D.:  Scary, I am glad you recovered. There are several answers. First, there are different species of Staph (Staphylococcus), some that cause disease (S. aureus) and some that can actually be helpful. So, it depends on what species has colonized you. Second, it depends where the bacteria is on your body. S. epidermidis is a normal part of most peoples skin. But, if it gets into your blood via a wound it can cause disease.
Southeastern Greene School District in PA (12th grade student)

How do skin cells become stem cells?
Jon R. Lorsch, Ph.D.:  In order to turn a skin cell into a stem cell, scientists have to treat the skin cells with a combination of viruses that contain several different genes. Once these viruses get into the skin cells they make the proteins that are encoded by these genes. These proteins cause the skin cells to turn into stem cells. The stem cells can then be triggered to change (differentiate) into other kinds of cells. Scientists are working hard to try to understand exactly how these processes work so that we can find even better ways to turn adult cells back into stem cells.
Webutuck High School in NY (9th grade student)

If the cure for cancer was found from stem cell research, how would we control population?
Jessica Faupel-Badger, Ph.D.:  If you are interested in cell populations, there are many regulators of the cell cycle that ensure the cell divides only when given the appropriate cues. Cancer treatments focus on eliminating cells that divide outside of these limits or these treatments could try to restore this regulation of the cell cycle.
Southeastern Greene School District in PA (12th grade student)

What color are cells?
Alexandra Ainsztein, Ph.D.:  Cells are colorless. While cells with lots of iron, like red blood cells may be red, usually cell are colorless. Biologists use dyes to false color fixed cells or attach fluorescent tags to proteins to create beautiful images. This does not occur naturally.
Webutuck High School in NY (9th grade student)

What are the major draw backs in stem cell research? Why do some people think its wrong?
Brian Pike, Ph.D.:  Thanks for this interesting and thoughtful question. One drawback to applying stem cell research to humans is that we do not yet fully understand most of the cellular mechanisms that control stem cell growth. One concern is that stem cell treatment could lead to uncontrolled cell growth (i.e., cancer). But these issues should not hinder us from learning more about these unique cells. Some people think stem cell research is wrong because they do not have enough knowledge or understanding to appreciate the potential. Some people are also opposed to using embryonic stem cells.
Southeastern Greene School District in PA (11th grade student)

Information - Moderator Moderator:  Keep the questions coming! We currently have experts in cell biology, genetics, biophysics, cancer, and microbiology.

Are there any dangerous stem cell treatments?
Brian Pike, Ph.D.:  Currently there are no approved stem cell treatments in humans. Much research still needs to be done to make it as safe as possible. Once potential concern is that stem cells, because of their robust tendency to grow and divide, could become cancerous. But the promise of stem cell therapy is tremendous and scientists and medical doctors are learning more every day. Thanks for your question!
Southeastern Greene School District in PA (11th grade student)

How can we isolate stem cells from different tissues?
Jon R. Lorsch, Ph.D.:  Great question! There are two main ways scientists can isolate stem cells from tissues. The first is called "enrichment." Stem cells have special proteins on their surfaces and these proteins can be used as handles to grab stem cells and purify them away from non-stem cells. The other approach is called "depletion." In this technique cells from a tissue are put onto a plate that only allows stem cells to grow. This gets rid of all the non-stem cells. Either way, it's a lot like panning for gold.
Southeastern Greene School District in PA (11th grade student)

How many different types of cells can be found inside the human body?
Alexandra Ainsztein, Ph.D.:  Good question. There are about 200 cell types and a few trillion cells in the human body. That does not include bacteria, fungus and mites that live on the body.
Spencer Middle School in WV (8th grade student)

If the cure for cancer was found through stem cell research, how would we control human population?
Donna Krasnewich, M.D., Ph.D.:  This is an interesting question. Thinking about this the first thing that comes to mind is that cancer, which has significant impact on those affected, is only one of many diseases that affect us. So, even if a cure was found for cancer, which we all hope happens someday, there will always be another disease that will concern us. Also, aging research suggests that humans have an defined life span because the human as an organism "ages". For example, eventually cells can't reproduce and replace each other, or toxins from the years build up and shut down our cells. There are many hypotheses for why human age. So at this point in history, humans still have defined life spans and there are many diseases out there. We hope that this helps you to think about studying both human diseases and normal human biologic processes like aging.
Southeastern Greene School District in PA (12th grade student)

Can things such as hair spray affect cells?
Brian Pike, Ph.D.:  Thanks for your question. Hair spray itself is generally considered safe as long as you use the product as intended. However, many products in our environment that we use on a day-to-day basis could be harmful if one has too much exposure to them or is exposed at high concentrations. You should always use any product as intended and be sure to use hair spray in a well ventilated area!
New Century Technology High School in AL (teacher)

Which cell were probably the first cells on Earth?
Darren Sledjeski, Ph.D.:  It is generally thought that bacteria-like cells (prokaryotes) are the first types of cells found on Earth. They are believed to have appeared about 4 billion years ago. Evidence for the most ancient forms of life are found in fossils called stromatolites. These bacteria were probably chemoautotrophs. That is, they ate chemicals found in the environment.
New Century Technology High School in AL (teacher)

Thank you for hosting Cell Day! This is our 3rd year participating! My students learn so much from the chat room! We threw a big party this year to cell-a-brate!
Joe Gindhart, Ph.D.:  Thank you for your participation! We couldn't do Cell Day without involvement of schools like yours. If you like, you can send us a picture of today's class asking questions; the email address is info@nigms.nih.gov. Thanks again!
Southeastern Greene School District in PA (12th grade teacher)

Will there ever be a way to cure people with Sickle Cell Anemia?
Ward Smith, Ph.D.:  This is hard to predict. The great thing about science, where research leads you is not predictable. Sickle cell is caused by a single change (mutation) resulting in the replacement of one amino acid in hemoglobin leading to red cell deformation in the blood. I am confident that research will eventually find a cure for this, but I cannot predict when.
New Century Technology High School in AL (teacher)

Do skin cells stretch or multiply when you gain weight?
Alexandra Ainsztein, Ph.D.:  The size of cells are tightly regulated and maintained so they do not stretch much. As the surface area of the body increases with weight gain the number of skin cells increases.
New Century Technology High School in AL (teacher)

How can you predict how many cells are in an animal?
Brian Pike, Ph.D.:  Thanks for another good question! Scientists can estimate the number of cells in a person or animal by taking small samples of tissue and doing cell counts in the sample. Knowing the density and size/weight of the tissue and of the animal, one can then extrapolate to estimate the total number of cells. The number of cells in a human is thought to be a few trillion cells.
Southeastern Greene School District in PA (11th grade student)

How long did it take for you to become a scientist?
Jessica Faupel-Badger, Ph.D.:  This is a great question! There are many different career options for scientists and all require various levels of formal education. You can decide to major in a science area, such as biology or chemistry, as an undergraduate student in college. Many people find employment in research settings after this. Other options include gaining additional and more specialized education through master or doctoral degree programs. In most cases, scientists who are leading laboratories have attained a doctoral degree and completed a stage of training known as postdoctoral training. This combined doctoral and postdoctoral training, on average, can be 8-10 years beyond the undergraduate degree. Being a scientist is a great career path and I encourage you to consider starting this journey!
New Century Technology High School in AL (teacher)

What is a scientist's daily work day like? Is all of your time spent in a lab testing or like in a office throwing ideas around?
Jon R. Lorsch, Ph.D.:  There are lots of different kinds of jobs a scientist can have. Many work in labs where they get to do experiments AND throw ideas around, often at the same time (if they can multi-task). Working in a lab is a lot of fun - you learn things about the world that no one has known before (how cool is that?). Other important jobs that scientists can do include writing about science as a journalist, helping other scientists patent new technologies they invent as a patent agent or lawyer, or working on important scientific policy issues for the government or other organizations. One thing I can guarantee you of - you are never bored as a scientist!
New Century Technology High School in AL (teacher)

What is the rarest cell in a human?
Alexandra Ainsztein, Ph.D.:  Interesting question, but one that does not really have an answer. These cells would be seen during disease states such as tumor-initiating cells or rare genetic disorders.
Spencer Middle School in WV (8th grade student)

What is the most hands on career with cells?
Ward Smith, Ph.D.:  Cell Biology is the science of understanding how all cells function. If you are interested in working with cells, may fields use cells in one way or another, but cell biology is certainly one to consider.
New Century Technology High School in AL (teacher)

If the microscope was not invented, how do you think modern day science would be?
Darren Sledjeski, Ph.D.:  Interesting question. My guess is that science would be way behind from where we are today. Especially in our knowledge of infectious diseases. Before the invention of the microscope there were many theories about what made people sick. Bad air (malaria), an imbalance in our blood or lymph etc. Without knowing what made us sick no one knew how to effectively treat the illness. So, if you had a sore throat instead of getting a dose of an antibiotic or antiviral they might treat you with leeches or by bleeding you.
New Century Technology High School in AL (teacher)

What type of cells have cytoskeletons?
Joe Gindhart, Ph.D.:  I'm pretty sure that all cells have cytoskeletons. Eukaryotic cells have cytoskeletons made of actin (actin filaments), tubulin (microtubules), and intermediate filaments. Recent research has shown that bacterial cells also have cytoskeletal proteins that are important for cell division and compartmentalization. Understanding how the cytoskeleton works is one of the most active fields in cell biology.
Salk School of Science in NY (6th grade student)

What kind of classes would you have to take in college to if you want to study cells?
Donna Krasnewich, M.D., Ph.D.:  College is a very exciting time to learn, there are many different academic directions to go. Typically students interested in biology and cells will study chemistry, biology and math. Chemistry comes in many flavors; inorganic chemistry gives the basics of the characteristics of elements and how they work together. Organic chemistry is really fun, in this class you study the complex reactions of molecules with carbon in them, many of these are the basis of life. Besides that you will study biology, cell biology and of course, genetics, how DNA codes for the features of cells. The one field that we think is very important is math. Students who are strong in math have a unique perspective on biologic structures and networks. This is a growing niche in biology and very, very exciting. There is so much to learn.
New Century Technology High School in AL (teacher)

Are there any other ways for a cell to make food other photosynthesis and how do they work if there are?
Ward Smith, Ph.D.:  The cell requires sources of energy from food, from sunshine, from many sources. Cells have adapted to using many sources of nutrients in their environment. Cells can live on many food sources.
Salk School of Science in NY (6th grade)

On average, how many cells will the human body have during its entire lifetime?
Brian Pike, Ph.D.:  That's a good question and I don't have the exact answer. But in general, humans have a few trillion cells in total. The cells in the body are constantly dying off and being replaced by new cells. Some cells, such as skin cells, are constantly being shed and replaced. Other cells such as neurons, can survive in the brain for decades with very little turnover (cellular replacement).
New Century Technology High School in AL (teacher)

How do cells in the human body function without nuclei?
Jessica Faupel-Badger, Ph.D.:  Thank you for your question! Red blood cells do not have a nucleus or many of the other organelles typically found in other cell types in the body. This allows the red blood cells to have more space to carry oxygen bound to a protein known as hemoglobin. This highlights how different cell types have very specialized functions and can be organized in different ways to meet these specific needs.
Salk School of Science in NY (6th grade)

What is the smallest cell?
Darren Sledjeski, Ph.D.:  Good question and there are many answers. The smallest cell is is probably a bacterial cell. There are many candidates and the answer is regularly changing. Mycoplasma (200-300 nanometers in diameter) tend to be the smallest cells. But, recent research has identified potentially even smaller cells, like Peligiabacter and Nanoarchaeum. There is still some controversy over who the winner would be. And as we learn more about life on Earth we might find even smaller cells.
New Century Technology High School in AL (teacher)

What is the biggest problem you've encountered while working with cells?
Alexandra Ainsztein, Ph.D.:  Cells are fun to work with, but they do not behave uniformly especially when you use cell lines such as HeLa cells. To get around this issue one has to be mindful of the experiments you ask. When imaging cells, one needs to look at a lot of cells and group phenotypes. Scientists are transitioning to using stem cells which has eliminate some of these difficulties. Unlike in a given HeLa cell population which has variable chromosome numbers, stem cells have an identical number of chromosomes and likely to behave the same.
New Century Technology High School in AL (teacher)

Why don't animals get to make their own food?
Ward Smith, Ph.D.:  Some animals have evolved to derive the energy needed for life from many sources. Humans have evolved to take in some of their nutrients in this way (vitamins) but still derive the energy and nutrients from many sources.
Salk School of Science in NY (6th grade student)

How have advances in the field of cells, genetics, or science in general necessarily affected society? (
Jon R. Lorsch, Ph.D.:  Science affects society in many ways. For example, as we learn more about how cells work, we can use this information to help develop new treatments for diseases. These treatments can let people live longer, healthier lives and contribute to society for longer periods of time. Scientific research also leads to new technologies which can be used to start new companies and help advance the economy. In 2011, the U.S. medical innovation sector of our economy employed 1 million U.S. citizens, generated $84 billion in salaries and led to $90 billion of annual exports.
New Century Technology High School in AL (teacher)

What is the most interesting discovery that you have made about cells?
Joe Gindhart, Ph.D.:  Thanks for asking! I worked for many years on understanding how the microtubule motor protein kinesin moves organelles in the nervous system. I showed that the part of kinesin that attaches to its cargos is required for viability in fruit flies; later, other researchers showed that it is important in mammals, too. Scientists love to tell stories about their work.
Salk School of Science in NY (6th grade)

How does cancer enter a cell?
Jessica Faupel-Badger, Ph.D.:  I like this question! Cancer does not enter a cell, rather a normal cell is transformed into a cancer cell. Therefore, cancer starts within the cell. The early events in this process involve mutations in the DNA or deregulation of the protein products through other mechanisms. Our current understanding of cancer comes from important findings in this area and led to two scientist from the United States receiving the Nobel Prize in 1989!
Salk School of Science in NY (6th grade)

Approximately how many cells are in the average human body at a given time?
Brian Pike, Ph.D.:  Thanks for your question. At any given time your body contains trillions of cells, organized into more than 200 major types. Interestingly, your body also has about 10 times that number of bacterial cells in and on your body. The human stomach typically has 4-5 pounds of bacteria in it, and scientists are learning that these gut bacteria play an important role in digestion and the immune response.
Salk School of Science in NY (6th grade student)

What is the difference between red blood cells and white blood cells?
Darren Sledjeski, Ph.D.:  Red blood cells contain lots of hemoglobin which helps to transport oxygen to our cells and carbon dioxide away from our cells. To transport oxygen red blood cells contain iron. When you mix iron and oxygen you get the red color. White blood cells contain little hemoglobin and so do not absorb any particular color of light. Some organisms use copper instead of iron to transport oxygen and so their blood is blue.
Salk School of Science in NY (6th grade student)

Why do cells self destruct?
Brian Pike, Ph.D.:  That is a great question and is also a very interesting area of scientific research. The term for cellular self destruction is "apoptosis" or "programmed cell death." Apoptosis is very important for normal development of animals as it as it ensures that we do not have too many cells and that cells that are not healthy can be eliminated without causing harm to the surrounding cells. For instance, did you know that human embryos having webbing between their fingers and toes (just like ducks!)? Apoptosis is used to eliminate the cells that form the web so that you are born with toes and fingers and not duck feet. Cells can also undergo apoptosis when they are invaded by viruses as way to try and kill the virus and limit infection. But viruses are very tricky and they can often fool the cell into "thinking" that it has not been invaded. Thanks again for your question.
Salk School of Science in NY (6th grade)

Since chemotherapy's goal is to kill cancer cells, why does it cause hair loss?
Jessica Faupel-Badger, Ph.D.:  Great and important question! The type of chemotherapy you are referring to targets cell division processes. Therefore, in addition to the cancer cells, rapidly dividing cells such as hair cells and cells lining the intestine are also affected by this treatment. With greater understanding of the molecular changes whereby a normal cell becomes a cancer cell, therapies more targeted to only the cancer cells are being developed.
New Century Technology High School in AL (teacher)

How does the cell membrane decide what can go in and out of cells?
Alexandra Ainsztein, Ph.D.:  Cells use multiple modes to transport proteins (receptors and channels), viruses (attachment to another protein or in a vesicle), and small molecules (diffusion) across the cell membrane, and determine whether they will be transported. A distinguishing feature of diffusion is that it results in mixing or mass transport, without requiring bulk motion. Receptor binding and channels open and close can be triggered by environmental needs, cell nutrition, cell stress. This orchestrated cellular dance is complicated.
Salk School of Science in NY (6th grade)

We are also having a cell party, today, complete with edible cells. What is the effect of large amounts of sugar on cells?
Donna Krasnewich, M.D., Ph.D.:  We all laughed when we saw this question, we wish we were there! Sugar plays many roles in our bodies. The one that we think about first is for nourishment, our cells have transporters the move many types of sugar through the cell membranes. Once sugar gets through the cell membrane it is converted by the enzymes in the cell to ATP or NADPH which are the energy currencies of the cell. A cell tries to control how much sugar comes inside. If there is a lot of sugar outside the cell, the cell will not import all of it but the extra sugar will be filtered by our kidney and put in our urine to be excreted. The affect of too much sugar around a cell has different affects on different cells. For example, when the brains of children have lots of sugar around they get energized....I am sure you know what I mean. Fortunately, this is temporary because our body likes to keep our sugar levels about the same all the time. We excrete what we don't need. The less known use of sugars in cells is that they connect together to make larger structures called "oligosaccharides". These structures have functions in the cells, sort of like zip codes in cells or on proteins. Oligosaccharides are involved in cells recognizing other cells and proteins going to the right place. This function is probably less affected by that cell cake that you are eating right now. The study of sugar and how our body uses it is really exciting. More research will help us to understand diabetes (where cells don't control their sugar levels very well). Diabetes affects many people. Young scientists thinking about solutions to the problems caused by diabetes would be great! Study hard!
New Century Technology High School in AL (teacher)

What would happen if the chloroplast didn't exist
Darren Sledjeski, Ph.D.:  Without cholorplasts we probably wouldn't have plants. Plants use chloroplast to convert sunlight into glucose and oxygen via photosynthesis. Blue green algae can also photosynthesize but do not contain cholorplasts. There is some evidence that cholorplasts are in fact blue green algae that were taken up by eukaryotic cells long ago to form a symbiotic relationship.
Salk School of Science in NY (6th grade student)

Information - Moderator Moderator:  Wow! We're just over an hour in and we've already gotten a lot of great questions. We're looking forward to getting many more.

What exactly do chloroplasts do during photosynthesis. I understand that the process itself creates glucose and that it creates oxygen, but I don't know what the actual chloroplasts do during the process or how they do it.
Ward Smith, Ph.D.:  Chloroplasts are important for photosynthesis. In this process energy from the sun is converted into electrons which are then used to drive other reactions which use Co2 ultimately resulting in stored energy (glucose) and waste oxygen (respiration).
Salk School of Science in NY (6th grade)

What is the process of communication between cells?
Alexandra Ainsztein, Ph.D.:  There are different ways that cells communicate. Cells communicate by sending and receiving signals. Molecules can be transferred through cell junction when the cell is physically next to each other, but cells can also communicate along long distances. Each step in a signaling pathway provides an opportunity for cross-talk between different signals. Through cross-talk, the cell integrates information from many different signaling pathways to initiate an appropriate response.
Salk School of Science in NY (6th grade student)

How are cancerous cells different from eukaryotes?
Jessica Faupel-Badger, Ph.D.:  Cancer cells arise from the normal, eukaryotic cells. For example, colon cancer cells arise from the normal colon cells. Cancer cells differ from these untransformed, normal cells in many ways. Cancer cells acquire the ability to divide indefinitely without the normal regulation on the cell cycle. Cancer cells can continue to divide or survive under conditions where other cells would not. Cancer cells also may use different pathways for generating cellular energy.
Salk School of Science in NY (6th grade)

What is the most active type of cell in the body?
Susan Gregurick, Ph.D.:  Hi, fantastic question. We here at NIGMS have had a really active discussion about your question. There is some disagreement in the room about the winner for the most active type of cell in the body. Here's what we came up with (top few): Cardiac Cells: they have a really high density of mitochondria which allows them to produce ATP quickly and make these cells highly resistant to fatigue Muscle Cells: like cardiac cells, these also have the ability to produce ATP quickly. Neuron, or nerve Cells: are able to rapidly process and transmit information though electrical and chemical signals Skin cells: have the most cell turn over and the ability to rapidly regenerate. In fact these cells regenerate faster than any other cell type. Have a great cell day and thanks for your question.
New Century Technology High School in AL (teacher)

I am completing my Bachelor of Science in Cell Biology and Genetics but am unsure of my next step. What are other paths to take with this degree outside of laboratory research? Thanks!
Michael Bender, Ph.D.:  The great thing about training in cell biology and genetics is that it gives you the ability to understand the scientific basis of a really fast moving field that has amazingly broad implications for human health, medicine, biotechnology, law, ethics and more. This means that people with a science background can contribute something unique to a wide variety of careers and disciplines, from the business side of biotechnology or patent law, to policy careers advising on appropriate application of powerful new technologies like genome sequencing to medical treatments, to government positions like ours where we manage research portfolios and have a chance to foster important new discoveries. Sometimes the path to these types of careers leads through training beyond the undergraduate level in laboratory research but others find a job outside of science following the undergrad degree or pursue a degree in a different discipline and then look for the opportunity to apply their science background. I always suggest following your interest.
UMD in MD (student)

How long do cells live?
Donna Krasnewich, M.D., Ph.D.:  Different cells have live different lengths of time. For example, nerve cells rarely if ever divide and live a very long time. Red blood cells live about 120 days, once they mature from the stem cells in our bone marrow and move into the the blood stream. Then there are cells that are very short lived, typically those that exposed to the elements. You can almost guess what those are; skin cells, and the cells or our cornea (the surface of our eyes) and cells that line our gastrointestinal tract (including our mouth and gut) where lots of food passes by. These cells have to turnover rapidly, especially if they are damaged. Think about how fast a cut in your mouth heals and compare it to how long it takes to heal a cut on your skin. Your mouth heals much faster! Understanding why cells live longer and why cell die is a very active field of research. Thanks for joining us!
Salk School of Science in NY (6th grade student)

Do you think that at some point in the past when Mitochondria first became symbiotic with Prokaryotic cells as being the moment when large organisms started moving around on the Earth? It takes fuel (ATP) to move right?
Alexandra Ainsztein, Ph.D.:  This is a difficult question to answer. I would say maybe. Since all multicellular life contain mitochondria, it may be. However, the symbiotic event occurred so long before multicellular life developed, the connection between these events is tenuous.
Spencer Middle School in WV (8th grade teacher)

How does enzyme replacement therapy work? Can enzymes be transplanted from person to person?
Ward Smith, Ph.D.:  Enzyme defects are treated in many ways. Newborns that cannot use tryptophan can be treated with dietary restrictions. Today, we can replace defective enzymes in some cases with genetic solutions, replacing defective genes that produce defective enzymes with corrected genes. This is the great promise for treatment of genetic defects with genetic medicine.
Adams Middle School in CT (8th grade student)

Do you feel that cells are being taught enough in the school systems, today?
Susan Gregurick, Ph.D.:  I wish that kids at every grade level could have more exposure to cell biology. There are exciting ideas to be learned. My favorite cell story was when I was helping my son learn more about DNA and bases (ATCG). We extracted the DNA from strawberries and then looked at the DNA under a microscope. He wondered why he couldn't see the ATCGs? Confused, I asked him what he meant. He thought that he would actually see the letters A, T, C and G! There is still so much to learn about cells so please keep teaching the next generation of scientists about this important field.
New Century Technology High School in AL (teacher)

For someone wanting to research cells as a career choice, what colleges do you suggest and what major(s) do you suggest?
Darren Sledjeski, Ph.D.:  Thanks for the question. If you want to be a cell researcher then you want to find a college that has an active undergraduate research program. That is, a school that provides the opportunity for students to actually do research. This will give you the opportunity to see what bench science is like (the joys and frustrations) as well as provide valuable training. 20 years ago I would have said get a biology degree. Now, with the explosion of data, especially in the area of genomics, having a math degree is also a viable path. I also know folks with engineering degrees who are doing research in biology. We need lots of people with diverse educational backgrounds to help us gain a deeper understanding of biology.
New Century Technology High School in AL (teacher)

What's the most complex cell you've encountered?
Jessica Faupel-Badger, Ph.D.:  Great question and one which would probably have a different answer from each person around the room right now! Cancer cells are very complex. Cancer cells can acquire the ability to divide and survive in the absence of normal positive and negative growth signals. Cancer cells also can invade tissues and survive in a foreign place, in the case of metastasis. The multiple molecular changes that typically occur over a long period of time make cancer cells very complex and vastly different from the normal cells from which the cancer developed.
New Century Technology High School in AL (teacher)

When cell communication goes wrong, is the risk of disease the only thing it results in?
Alexandra Ainsztein, Ph.D.:  When we talk about disease most people think about whole body effects that require recovery and possibly medical intervention. However, cell miscommunications are usually localized events that are dealt with quickly and do not result in a disease state.
New Century Technology High School in AL (teacher)

What did people think made up living things before cells were discovered?
Jon R. Lorsch, Ph.D.:  There were lots of ideas for the composition of living systems before Hooke discovered cells and then van Leeuwenhoek (say that ten times fast) showed that they were the units of life. One widespread one was that humans arose from tiny humans called animalcules (or homonculi) that were contained in either sperm or eggs. These animalcules were thought to simply grow and eventually become full-sized humans. I guess Hooke was expecting to see little people waving back at him when he first looked through his microscope (actually, he was looking at cork wood, so maybe he was expecting to see little trees waving back at him).
New Century Technology High School in AL (teacher)

If you cut a cell in half and then turn it upside down will the nucleus, ribosomes, and other parts of the cell fall out?
Joe Gindhart, Ph.D.:  Yes, sort of. Molecules and organelles in the cell are very small, and the cytoplasm is very viscous. The nucleus in the cytoplasm moves as well as we would if we were swimming in a pool of molasses. "Ooze out" might be a better term to use than "fall out". Google search "Life at Low Reynolds Number" for more information; it is a fascinating topic.
New Century Technology High School in AL (teacher)

How big is a cell in comparison to an atom?
Ward Smith, Ph.D.:  Cells range from a few micrometers (10 exp -6 meters) to 100 micrometers. Atoms are on the order of 1 Angstrom ( 10 exp -10 meters).
New Century Technology High School in AL (teacher)

What inspired you to work with cells?
Darren Sledjeski, Ph.D.:  I have always been interested in how things work. Toasters, TVs, telephones...etc. My inspiration came from watching NOVA science specials on TV. I was fascinated with the idea of understanding how cells "work." How do they know when to divide? How do they "know" when to stop dividing? How do they "know" where they are supposed to be in the body. I saw them as fascinating little machines and I wanted to know how they work. The answer is still incomplete and I am still fascinated with their inner workings.
New Century Technology High School in AL (teacher)

What happens as a cell increases in size?
Alexandra Ainsztein, Ph.D.:  Cell size and shape are highly regulated processes. Cell size can increase during disease states but typically it grows when the cell is preparing to divide. Cell membranes (lipids and cholesterol) and organelles (lysosomes, mitochondria, Golgi, etc.) duplicate. The chromosomes replicate and separate preparing for cell division and entry into the next cell cycle.
New Century Technology High School in AL (teacher)

Do our cells makes us a certain color like plant cells do?
Ward Smith, Ph.D.:  Color of skin arises from melanin, a molecule in skin. Plants are colored by may different pigments in plant cells, chloroplasts and many other molecules that confer color on the various parts of a plant such as flowers leaves etc.
New Century Technology High School in AL (teacher)

What happens to the cells when an individual loses weight?
Brian Pike, Ph.D.:  Thanks for your question! As you may already know, fat cells (known as adipocytes) in the body store excess energy from the food you eat as fat. The fat is stored in the cells in the form of fatty acids called triglycerides. As a person gains weight, more and more triglycerides are stored in the fat cells and the cell size expands. If enough fat cells get bigger, then that part of the body will start to look fatter. But if a person starts to exercise more and eat a healthier diet, the amount of fat in a fat cell is reduced and the fat cells start to shrink in size. Thus it is primarily the expansion and shrinkage of the fat cells that makes a person appear fatter or thinner as they increase or decrease their weight. Thanks for asking your question and happy cell day!
UMD in MD (student)

Why are centrioles not found in plant cell?
Joe Gindhart, Ph.D.:  That's a tough question. Some argue that plant cells have a rigid structure imposed by the cell wall, so they do not need centrioles to rapidly rearrange the cytoskeleton during mitosis. In interphase cells, centrioles are required to form cilia and flagella, but plant cells do not have these structures. Recent work has shown that many types of animal cells do not contain centrioles. This is a very active field of research, and NIGMS helps support scientists who study the cytoskeleton and centriole function.
New Century Technology High School in AL (teacher)

Do cells amaze you every time you study them ?
Donna Krasnewich, M.D., Ph.D.:  Cells and groups of cells are pretty cool, each very different. I love the images of cells that are on this link to the NIH/NIGMS cell image gallery images.nigms.nih.gov They are really beautiful. I also love to learn about how cells interact with each other, for example they stop growing when they know another cell is nearby, and they communicate with each other about making shapes (for example shaping your liver or your heart during your growth before birth). If you think about cells by themselves, with others in an organ, how they talk to each other during development or in the brain, our imaginations have lots of ground to cover. Research starts by learning as much as you can, developing a hypothesis and an approach to answer the question. I hope you stay curious and amazed! So much to do and to learn!
New Century Technology High School in AL (teacher)

Can you be a scientist dedicated to just a certain type of cell?
Jessica Faupel-Badger, Ph.D.:  Yes, scientists often become specialized in one area. This can be one disease, one cell type, one organelle or even one molecule. To make significant research advances in an area, scientists must understand that area in great detail to know the current limits of our knowledge, questions that need to be answered, and potential controversies. Yet, there are many examples of how advances in one area of science have spurred advances in another area. Therefore, it is important for scientists to have "deep" knowledge in a specific area but "broad" knowledge of other research areas in order to bring new and creative approaches to their work.
New Century Technology High School in AL (teacher)

Why do biologists think there are more prokaryotic cells inside the human body than there are eukaryotic cells? Are there really more prokaryotes than eukaryotic cells?
Darren Sledjeski, Ph.D.:  Insightful question. We were just discussing this amongst ourselves. We still do not have a complete inventory of the number of cells, prokaryotic or eukaryotic, in our bodies. The numbers we do have are estimates. But, we do know that bacterial cells are many many times smaller than eukaryotic cells. So in terms of absolute numbers there are probably many more. But, by volume there are less.
New Century Technology High School in AL (teacher)

What advancements in the study of cells have you most excited?
Jon R. Lorsch, Ph.D.:  We are very excited right now about new discoveries that allow scientists to make very precise changes to genomes in living cells. These new technologies came from studies of a newly-discovered antiviral system in bacteria called CRISPR. Once scientists figured out how the CRISPR system works in bacteria, they got the idea that they might be able to use parts of it to modify the genomes of mammalian cells - and it worked! Right now this is being used as a research tool to help us understand how mammalian cells work, but there is hope that eventually doctors might be able to repair damaged genes in people using this technology.
New Century Technology High School in AL (teacher)

What advice do you have for current students interested in the filed your in?
Susan Gregurick, Ph.D.:  The best advice I can give to any young person who would like become a scientist is to be sure to include classes in math. Mathematics is a great foundation for many other sciences, including cell biology.
New Century Technology High School in AL (teacher)

Can you please tell me about your career and how a high school student can prepare for a career in science? Thanks!
Michael Bender, Ph.D.:  I was interested in snakes and turtles when I was a kid and this seemed to lead to a biology major in college. I think the best way for a high school student to prepare for a career in science is to stay curious, ask lots of questions, and of course work hard in the biology, chemistry and math courses that are available to you. One thing to keep in mind is that all of these fields will likely be important to your main interest eventually -sometimes this is not clear when you first take the class. After college, I worked as a research technician in New York City, returned to Indiana for my Ph.D. studying developmental biology, then went to Stanford University in California for postdoctoral work on hormone signaling. I was a professor of Genetics at the University of Georgia for 16 years, and 5 years ago came to NIH where I manage grants in the areas of RNA processing and protein synthesis. I feel really fortunate for the opportunities that I have had to contribute to science and training in a lot of different ways.
Adams Middle School in CT (8th grade student)

Have human embryonic stem cells been used successfully to treat any human diseases yet?
Donna Krasnewich, M.D., Ph.D.:   There are many researchers working on this area, the field is called regenerative medicine. Here is a link to the NIH Regenerative Medicine site Regenerative Medicine There is great potential for improved medical care in this field but, as you can imagine, it is very complex.
New Century Technology High School in AL (teacher)

What happens to the cells in an animal when it hibernates? Do they do anything abnormal?
Alex Valm, Ph.D.:  When a mammal, like a bear hibernates, the animal's metabolism slows down dramatically. For example, energy intake stops because the animal is not eating, heart rate and breathing slow. Within cells, transcription of certain genes slows. Specialized fat storing cells called adipocytes provide energy to all the cells of the body by providing fat to other cells.
Manzano High School in NM (12th grade student)

What are the main three parts of a eukaryote cell?
Lee Slice, Ph.D.:  That is a good question. Eukaryotic cells have many compounds and structures but the cell membrane, the nucleus and the cytoplasm are the three main parts.
Webutuck High School in NY (9th grade student)

Why do animal cells not have cell walls?
Alexandra Ainsztein, Ph.D.:  Very very long long ago in evolution some cells survived better with cell walls and others changed to survive without it. Animal cells are much more flexible because they lack a cell wall. They do have an endoskeleton that protects the cell and keeps its shape.
New Century Technology High School in AL (teacher)

Would the research or continued research on stem cells possibly lead to a cure for say, breast cancer?
John Laffan, Ph.D.:  Yes, many laboratories are working on breast cancer stem cells which are responsible for the growth and spread of the cancer. A better understanding of these stem cells is essential to control breast cancer.
Manzano High School in NM (11th grade student)

How fast does it take for a cell to produce two daughter cells?
Alex Valm, Ph.D.:  That's a great question. Some cells, for example bacteria can produce daughter cells very fast when nutrients are available. The doubling time for E. coli bacteria is 20 minutes. Other cells in the human body take hours or days or even years to divide. All eukaryotic cells undergo a series of checkpoints during mitosis to ensure that the DNA and other parts of the cell are properly distributed into the two daughter cells.
Webutuck High School in NY (9th grade student)

When stem cells differentiate, how do they "know" which type of cell to become?
John Laffan, Ph.D.:  The stem cells respond to their environment. What cells are touching them as well as what hormones and other environmental clues are around drive what the stem cell will become.
Webutuck High School in NY (9th grade student)

How come skin is considered an organ if it is made up of dead skin cells?
Richard Okita, Ph.D.:  The skin is composed of several layers of living cells. The cells have unique properties because they provide structure and prevent liquids from passing through the skin into the body or proteins, and other cellular components from escaping from the body. Skin cells do have a finite life span and they do die and they will slough off.
Webutuck High School in NY (9th grade student)

What are some difference between mammalian stem cells and reptilian and amphibian stem cells?
Lee Slice, Ph.D.:  The definition of a stem cell is a cell that when it divides it produces at least one stem cell and that the daughter cells can become any cell in the organism. The fact that the cells are mammalian or reptile or amphibian just means that those cells will be used to generate that specific animal.
Manzano High School in NM (11th grade student)

What was your biggest discovery involving cells?
Alex Valm, Ph.D.:  Thanks for that question! My biggest discovery so far, is that bacterial cells that live in the human mouth form very complex structures and that these structures somehow influence health and disease in the mouth. Specifically, one big discovery is that cells of the genus Fusobacterium may not bind to many other kinds of cells, which was previously reported in the literature. You can read about it here: Nature News and Comment Link to external Web site
Antioch Charter Academy II in CA (7th grade student)

What are the differences between a virus and a bacteria?
Susan Gregurick, Ph.D.: Great question. Virus are really tiny agents that infect cells, including animal cells, plants cells and bacteria. They can replicate only inside a living cell. Bacteria, on the other hand are prokaryotic microorganism (they are small but larger than viruses). We around the room felt that viruses really push the limit of the question-are they a form of life, since they can't self replicate. I encourage you to consider thinking about the differences between bacteria and viruses too.
Manzano High School in NM (12th grade student)

Does a cell immediately die after it produces a daughter cell? If not, for how much longer does it continue to live?
Carrie Lucas, Ph.D.:  Great question! In general, cells do not die after producing a daughter cell. Instead, one cell becomes two and two become four, etc. This is what allows certain cells (e.g., immune cells) to rapidly increase in number in response to appropriate stimuli (e.g., infection). Different cell types in the body live for different durations of time.
Webutuck High School in NY (9th grade student)

How many cancer cells can reproduce in 24 hours?
Joe Gindhart, Ph.D.:  An interesting observation about cancer cells is that they typically do not divide faster than normal cells, but they divide more often because cancer cells do not "listen" to signals from surrounding cells that tell normal cells to stop dividing. The mammalian cell cycle is about 24 hours, so I would say that the answer is once. Thanks for your question!
Southeastern Greene School District in PA (9th grade student)

If someone is killed, how long does it take for their cells to shut down?
John Laffan, Ph.D.:  It depends on the cells. Some cells die after a few minutes (like brain cells), some can be recovered after 24 hours (like skin cells). If you consider the bacteria that live in the body as part of them, those bacterial cells can live and grow for weeks.
Antioch Charter Academy II in CA (7th grade student)

What could happen if there was a problem in the cell and if there is a problem, how can it be fixed
Lee Slice, Ph.D.:  Cells have specific ways to do housekeeping and the cleanup errors or problems. When a cell divides, it replicates all the chromosomes and sometimes there are mistakes make in making the new DNA in the chromosomes. The cell has specific proteins that proofread the DNA and correct errors. This is very important because if this is not done then chromosomal errors can cause cancer in people. The cell also has the ability to identify denatured proteins within the cell, which they then degrade in the lysozome. The disassembled protein parts can then be reused by the cell to make new proteins.
Antioch Charter Academy II in CA (8th grade student)

What do polar bodies do?
Michael Bender, Ph.D.:  This is a good question. Polar bodies are a product of meiotic divisions. In mammals, polar bodies eventually disintegrate, whereas the egg persists and can be fertilized. On the other hand, in plants, polar bodies can be fertilized by a sperm cell and become the endosperm while the ovum can be fertilized by another sperm cell and become the plant embryo.
Webutuck High School in NY (9th grade student)

Why does alcohol killed brain cells
Alex Valm, Ph.D.:  That's a great question. Specialized cells in the brain called neurons transmit signals using electricity and have a structure that is similar to electrical wires. Other specialized cells wrap around the neurons to insulate them, just as electrical wires are surrounded by rubber. The specialized insulator cells use fat to insulate. Alcohol can interfere with these cells, because fat will dissolve in alcohol, but not water. So, when a person drinks alcohol, some of it goes to the brain and dissolves the insulation around neurons. This prevents the neurons from properly sending their electrical signals. Over time, the neurons and other cells in the brain eventually die when they cannot properly function.
Southeastern Greene School District in PA (9th grade student)

Is it possible to have too many or not enough cells?
Carrie Lucas, Ph.D.:  Terrific question! The answer depends on cell type. For example, within the immune system, there are many examples of diseases that are caused by too many or not enough cells. When too many immune cells accumulate, patients get very large spleens and lymph nodes. When too few immune cells develop, patients have difficulty fighting infections.
Antioch Charter Academy II in CA (8th grade student)

How does alcohol kill body cells?
Alex Valm, Ph.D.:  Great question. I answered a similar question just now. You can look at question #114 about how alcohol kills brain cells. I would add that all cells in the body are insulated with a layer of fat-like molecules. This is the cell membrane. Alcohol can interfere with the cell membrane because the oily membrane dissolves in alcohol. With enough alcohol or over a long time, cells can die.
Southeastern Greene School District in PA (9th grade)

What field is there a need for new scientists?
Susan Gregurick, Ph.D.:  I would say that there is a need for scientists who can work at the interface between the biological and biomedical sciences and the data sciences. Knowing sophisticated mathematics and having computer skills to address questions like 'what does this biomedical data tell us about particular diseases' is still a challenge. In particular, as we at NIGMS see more and more data being produced every day, we have some big data challenges ahead!
PaCyber in PA (9th grade student)

If a species was to reproduce through incest how would it affect their genetic structure?
John Laffan, Ph.D.:  The more a species reproduces with more closely related individuals the less genetic variation is available to that species. This is not always bad but it does limit how well the species may respond to changes.
Manzano High School in NM (12th grade student)

What is the least needed/important cell in the human body?
Lee Slice, Ph.D.:  This is a good question. There is a lot of discussion here on that topic. Any one cell in a body is not that important because there are many others that can replace it or there is a way to replace the cell by the body's stem cells. So I would say the most important cells in the body are stem cells and conversely a fully differentiation cell like a red blood cell or an outer skin cell are lost in large numbers everyday.
Spencer Middle School in WV (8th grade student)

What are eukaryotic cells,and what do they do?
Alex Valm, Ph.D.:  Eukaryotic cells are cells that have a nucleus and other organelles, in contrast to prokaryotic cells which do not have nuclei. Eukaryotic cells can be single celled organisms like amoeba or they can be parts of larger organisms like fungi, plants and animals. Eukaryotic cells perform all the functions necessary to keep the cell and the organism alive including energy metabolism.
Antioch Charter Academy II in CA (7th grade student)

How can cells communicate?
Joe Gindhart, Ph.D.:  Hi, thanks for your question. My colleague Alexandra answered this question earlier (Q# 69). Briefly, cells communicate by touching each other, sending chemical or electrical signals to adjacent cells, or by sending hormone signals to cells at distant locations. Have a great Cell Day!
Southeastern Greene School District in PA (9th grade student)

What classes would you recommend for one wanting to become a veterinarian?
Richard Okita, Ph.D.:  This is a great question. My wife's niece recently graduated from vet school. Initially, you need your basic science courses - biology, chemistry, math, physics to provide you your foundation in medicine. You will need training in immunology, pharmacology, bacteriology - infectious diseases, pathology, nutrition, surgery, and other courses which you obtain in college and when you enter vet school. You may want to volunteer or work for a veterinarian clinic and hospital while you are in high school or college to become familiar with the different jobs a vet has to do.
Manzano High School in NM (12th grade student)

Why does a sperm cell look so much different from an egg cell?
Michael Bender, Ph.D.:  These cells are specialized for their functions. Sperm cells need to deliver DNA from the father to the egg cell so that an embryo can be formed. The egg cell needs to contain DNA from the mother and contain enough nutrients to support the early development of an embryo.
Southeastern Greene School District in PA (9th grade student)

Does ATP ever break down?
Alex Valm, Ph.D.:  That's a great question! ATP is the energy carrier in the cell. One of the reasons this molecule is used by cells as the energy carrier is that it is easily recycled. One of the precursors of ATP is ADP. To make ATP, enzymes in the cell attach a high energy phosphate group to the ADP molecule. Now the ATP travels to where it is needed, and the high energy phosphate bond is broken, releasing energy and forming ADP. Cells have many mechanisms to detect damaged molecules in the cell. If the ATP becomes damaged, it may be further broken down and recycled.
Southeastern Greene School District in PA (9th grade student)

How long does it take to create new brain cells after other brain cells die?
Carrie Lucas, Ph.D.:  This is a fascinating question that is still being actively studied. Biologists used to think that new brain cells only developed very early in life when the brain was forming. More recently, we have learned that new brain cells can also be made in adults from important cells called neural stem cells. The exact time it takes to create new brain cells is still being examined, but some studies have suggested it takes at least 6 months for a new brain cell to mature. pnas.org Link to external Web site
Antioch Charter Academy II in CA (7th grade student)

How is bone cancer cells different from colon cancer cells?
Lee Slice, Ph.D.:  This is an interesting question. The general trait of a cancer cell is unregulated cell division that disrupts the function of the organ or region that the cancer cells are located. When this disruption is large enough to cause organ failure, then this leads to death. Where the cancer cell originates and from what type of cell effects the behavior of the cancer cells. Colon cancer originates from the epithelial cells that line the colon and it takes about 5 years to go from a precancerous cell to colon cancer. Colon cancer is totally preventable by colonoscopy screening. So everyone over 50 should be screened.
Southeastern Greene School District in PA (9th grade student)

Where do stem cells come from?
Joe Gindhart, Ph.D.:  While we often talk about stem cells in a petri dish that can be used to form organs or even a whole organism, stem cells are found in many tissues of the body. For example, our bone marrow has stem cells that divide and differentiate to form the variety of blood cells that circulate in our veins and arteries. Our liver has stem cells that divide in response to injury to liver tissue. So I guess that means stem cells come from normal developmental processes within our bodies, but they can be extracted for use in biological research and development of therapies.
Southeastern Greene School District in PA (9th grade student)

In astrobiology, how can we expect the cells of extraterrestrial life to differ from those found on earth
John Laffan, Ph.D.:  Great question. But even terrestrial cells have incredible variety. An ostrich egg, a leaf cell, and a human neuron are all cells but have very little apparently in common. Fundamentally, we expect cells to replicate and get nutrients from the environment. So to be recognized as cells it would have to have those functions. They may have all kinds of other features some of which may exist in terrestrial cells (but maybe not together) and some features that we have never seen before, even if they are from earth-like planets. If they are from planets with different atmospheres then we would expect even more differences.
Manzano High School in NM (11th grade student)

Why do we have different blood types?
Richard Okita, Ph.D.:  We have developed different blood cells to carry out a variety of specialized functions and it is most convenient to have these cells travel through our blood vessels. Red blood cells have a specialized protein, hemoglobin, which can capture oxygen molecules and carry them throughout the body. White cells are composed of many different cell types - some are for defense attacking microbes when they invade our bodies. Some will engulf bacteria and kill them. Other white cells are producing antibodies which will bind to microbes and viruses and help kill them. Another blood cell is the platelet. Platelets become activated when we suffer a cut or a wound and we begin to bleed. They are involved in the process of forming a blood clot to stop the bleeding.
Antioch Charter Academy II in CA (7th grade student)

How many cells are in the average adult human body?
Joe Gindhart, Ph.D.:  Your body contains trillions of cells, organized into more than 200 major types. Thanks for asking; have a great Cell Day!
Southeastern Greene School District in PA (9th grade student)

Are there any cells in the human body that can't get cancer?
Carrie Lucas, Ph.D.:  Hello Southeastern Greene School District! Thanks for your question. In general, fully differentiated cells will not become cancerous because they don't divide.
Southeastern Greene School District in PA (9th grade student)

Do all prokaryotes produce ATP by fermentation?
Susan Gregurick, Ph.D.:  I love your question because my hobby is fermentation, or Zymology. That is to say that I brew beer, which is the fermentation of sugars into ethanol and carbon dioxide by yeast. Okay, you got me, yeast are Eukaryotic fungi and my favorite one is Saccharomyces cerevisiae. Recently I tried using Bacillus subtilis, which is a gram-positive bacteria, eg prokaryote. Indeed, fermentation to carbon dioxide and ethanol happened only much slower (although more ethanol and CO2 was produced in the end). To get to your question, prokaryotes that rely on anaerobic pathways to produce ATP do so by fermentation.
Webutuck High School in NY (9th grade student)

When you are strength training how does your muscle cells get bigger, and can I grow new muscle cells. My teacher told me that you don't grow new fat cells and nerve cells after after a certain point.
Alex Valm, Ph.D.:  When you strength train, for example by lifting weights, the cells in your muscles actually get damaged. In response, the cells produce more proteins that are involved in muscle contraction. As the cells increase these contractile elements, they get bigger and your muscles are able to lift heavier objects without getting damaged. It was thought for a very long time that certain cells in the body do not reproduce after a certain point. Recent work has surprised the research field by showing that many tissues including those in the brain contain stem cells that are able to divide throughout a person's life. This was an unexpected discovery. A hot area of research is to understand how to make these stem cells form new cells when differentiated cells are damaged.
Southeastern Greene School District in PA (9th grade student)

On average which process take a longer amount of time to complete; mitosis or meiosis?
Carrie Lucas, Ph.D.:  Good afternoon! There are more steps in meiosis than in mitosis, which makes the process of meiosis take longer.
Manzano High School in NM (12th grade student)

Why does your hair keep growing after you die?
Lee Slice, Ph.D.:  Tales from the Crypt? Hair growth occurs in hair follicles that are in their growth cycle. This is an energy requiring process and thus needs a live cell. Therefore, dead cells do not make new hair. It appears that way because the skin surrounding hair shrinks making the hair look longer.
Antioch Charter Academy II in CA (8th grade student)

If I slam my finger in a door, do any cells die? What happens?
Richard Okita, Ph.D.:  When you slam your finger and suffer a wound or a cut, cells will die. Skin cells will be crushed and die. If you see bleeding or bruising there has been blood vessel damage so cells lining the vessels will have to be repaired and replaced. Blood cells will have escaped and they will die.
Antioch Charter Academy II in CA (7th grade student)

When a person dies from natural causes what happens to their cells?
Lee Slice, Ph.D.:  Well, this is an interesting question. People are made of cells and cells are make up of proteins, lipids, nucleic acids and minerals. Active, alive cells require energy to maintain themselves. When a person dies, their cells die and can no longer function. The proteins, lipids, nucleic acids and minerals are used by microbes and these microbes disassemble the dead cells. Generally, only the bones last for years after death but eventually they degrade into elemental parts.
PaCyber in PA (9th grade student)

How do cells make proteins?
Michael Bender, Ph.D.:  Cells make proteins by translating a messenger RNA using the ribosome, which is a complex of proteins and ribosomal RNAs. The ribosome is capable of decoding the information in the messenger RNA to form proteins by linking together a series of individual amino acids. There are a lot of moving parts in protein synthesis -you can find some good animations showing how it works on YouTube.
Southeastern Greene School District in PA (9th grade student)

If we don't form any new muscle cells, how exactly does muscle grow? Do the muscle cells really "tear?"
John Laffan, Ph.D.:  Each muscle cell already there gets bigger (hypertrophy) and better vascularized (more blood vessels) and better at creating energy (more mitochondria). Yes, you can really tear a muscle, this is not fun. You can also tear where the muscle attaches to the bones (also not fun but less cell death).
Manzano High School in NM (12th grade student)

Do neurons reproduce? If not, why?
Carrie Lucas, Ph.D.:  Interesting question. Most of our brain cells develop every early in life. Later in life, neuron cell division is limited, which may be an important way to avoid damage that would be caused by disrupting neural connections.
Antioch Charter Academy II in CA (7th grade student)

How many mitochondria are in a cell?
Alex Valm, Ph.D.:  The number of mitochondria in cells can be quite variable. Some cells have hundreds of small mitochondria. Since mitochondria are the energy producers, cells that require a lot of energy like the muscle cells of the heart have more mitochondrial mass than quiescent cells. A recent discovery from NIH researchers is that during nutrient starvation, cells reduce the number of mitochondria. The individual mitochondria fuse to form a large tubular network, presumably to protect the mitochondria from degradation. You can read about this research here: PNAS
New Century Technology High School in AL (teacher)

In the future do you think that viruses can evolve into forms that qualify as living organisms?
John Laffan, Ph.D.:  The virus itself will not evolve into a living organism (it is missing too much to ever be alive) but often viruses get stuck in their hosts? cells and evolve there. The human genome has many defunct viruses (and parts of viruses) lodged in it.
New Century Technology High School in AL (teacher)

Are non-living things able to have cells, and if they do can they reproduce?
Joe Gindhart, Ph.D.:  That is an interesting question. Robert Hooke first identified cells by looking at thin slices of cork. The small chambers he saw reminded him of the cells in a monastery; that's where the name "cell" came from. The cork had cells, but it could not reproduce. I'm sure there are synthetic materials that look like cells (like bubble wrap), but cannot reproduce.
Southeastern Greene School District in PA (9th grade student)

Is it possible to create a whole new species by re-arranging the DNA structure of a living organism and combine atoms to form new organelles? Has it been done before?
Lee Slice, Ph.D.:  This is a good question. Your question is basically describing the process of evolution. New species arise from changes in the DNA of ancestors over hundreds of thousands of years. More information on this can be found. Evolution
Jane Addams Middle School in IL (8th grade student)

To you what is the main part of a cell, that helps it function correctly?
Michael Bender, Ph.D.:  My background is genetics so I would say that the DNA, contained in the nucleus, is the most important part of the cell to help it function correctly. This is because DNA contains the information needed to produce all the parts of the cell, to control the functions of the cell, to specify the final form of the organism, and to respond appropriately to the environment. Others in our room disagree -some say mitochondria, the ribosome, or cell membranes like the endoplasmic reticulum are the most important. You could have a debate in your classroom about this because there is no one right answer!
PaCyber in PA (9th grade student)

What is the hardest working cell in the body?
Stefan Maas, Ph.D.:  Well, in terms of how much energy the cell is using, this might be cardiac myocytes (heart muscle cells), which have to keep contracting all the time and throughout live of the organism. You might also look back at the answer to question #72, which mentions a few other types of cells that are very active based on their specialized functions.
Southeastern Greene School District in PA (9th grade student)

For cancer cells how long does it take for cells to start affecting the body?
Carrie Lucas, Ph.D.:  Terrific question! The thing that has made cancer so difficult to treat is that every type of cancer is different. Even within the same type of cancer, there is variability in how quickly the cancer cells would affect the body and health of the patient. Some of the major factors that determine effects on the body are the location of the cancer, how rapidly the cells divide, and if the cancer cells have entered the bloodstream.
PaCyber in PA (9th grade student)

Could a black hole bend space time so much that you can travel through time?
Joe Gindhart, Ph.D.:  While we have many Ph.D.s in the room answering cell biology questions, we do not have Dr. Who in the room. We will ask him your question if he appears. Thanks for your interest in Cell Day!
Carmicheals in PA (12th grade student)

If possible, is there a way for a human to use photosynthesis if he/she had plant cells in their body?
Richard Okita, Ph.D.:  Your question reminds me of some of the science fiction monster movies I used to watch when I was much younger. In theory this is possible, but it would be highly unlikely. For photosynthesis, the plant cells would have to be near the surface because they would need sunlight to carry out photosynthesis. The reason I think it would be unlikely is because plant cells would be foreign to our bodies and they would generate an immune response and would be rejected.
Southeastern Greene School District in PA (9th grade student)

Because we all have different blood types, does that mean that we have evolved to specialize in different things i.e. foods, antibiotics, etc?
Joe Gindhart, Ph.D.:  That is a really interesting question. I have heard ideas about how individuals with different blood types have different susceptibilities to disease and pathogenic organisms. However, this is a topic that requires more research to draw stronger conclusions. In evolutionary terms, diversity within a population increases its chances of survival.
New Century Technology High School in AL (teacher)

When your brain is injured how does it repair itself?
Susan Haynes, Ph.D.:  Good question, and very timely, with all the interest in concussions and other types of brain injury. After the brain is injured, some cells die but others start working to repair the damage. The NIH has information on the latest research on concussions at http://newsinhealth.nih.gov/issue/jan2014/capsule1. Also, scientists used to think that if a nerve cell was injured and died, it couldn't be replaced by a new cell. But now we know that nerves can regenerate, at least to some extent. There is a lot of research going on to figure out how to enhance this natural regeneration to treat diseases that cause specific nerves in the brain to degenerate.
Southeastern Greene School District in PA (9th grade student)

If possible, can cells combine to form new cells with other cells, and if they can change the way an animal, human, plants look or act?
John Laffan, Ph.D.:  Cells can engulf other cells, the engulfed cell is called an endosymbiont. Rhizobia (nitrogen fixing bacteria) are engulfed by certain plant roots. This changes the appearance of the root (they form root nodules) and their function (that fixed nitrogen from the atmosphere) is now available to the plant. We think that eukaryotes formed when some cells engulfed other cells. The engulfed cells evolved to become organelles in the cell like mitochondria and chloroplasts (both of which still even still have their own DNA, but can no longer live on their own).
Southeastern Greene School District in PA (9th grade student)

Do arguments occur in the cell science "community"? If so what are they?
Michael Bender, Ph.D.:  Arguments are actually encouraged in the cell science community because discussion, debate, new evidence, and fresh interpretation of existing data leads to a better understanding of how cells work. I asked the room for famous arguments and they suggested three. At one time, people argued about whether the genetic material was DNA or protein or something else -we know today it is DNA. People argued about the cause of ulcers and the solution to this problem led to a Nobel Prize for Dr. Marshall and Dr. Warren for discovery of the role of the bacteria Helicobacter pylori and in peptic ulcer disease. The basis of prion diseases is another.
New Century Technology High School in AL (teacher)

Information - Moderator Moderator:  We have experts here who can talk about genetics, molecular biology, microbiology, immunology, and glycobiology. Or do you have questions about the cool tools used to study cells?

How are cells like a community ?
Alex Valm, Ph.D.:  That's a great question! The cells that make up the tissues of the body work together as a community for proper organ function and health. For example, cells in the body communicate with each other via chemical messenger molecules. Cells also sense when they touch each other. This is important so that cells know when to stop dividing so they don't get too crowded. Recently we have learned that even bacterial cells that were thought to live alone in the environment as single cells often live together with other bacteria as communities. An active area of research at NIH is how the microbial cells that live on and in the body function together as a community in health and disease. You can read about that research here: Human Microbiome Project News Release
Antioch Charter Academy II in CA (7th grade student)

Why isn't there a cure/vaccine for cancer?
Carrie Lucas, Ph.D.:  Good afternoon! Thanks for your interesting question. The major difficulty is that cancer is actually a collection of many different diseases. This is why one cure for all cancer is so difficult to find. However, we do have vaccines for some specific forms of cancer. One great example of a vaccine that prevents a form of cancer is the HPV (human papillomavirus) vaccine that induces an immune response to prevent infection with this virus that causes cervical cancer.
Central in NC (9th grade student)

hi

Joe Gindhart, Ph.D.:  Hi! My favorite organelle is the rough endoplasmic reticulum. How about you? Thanks for your interest in Cell Day.
Elizabeth Andrews High School in HI (11th grade)

Lets talk about genes and I don't mean trousers. How do genes determine our traits?
Lee Slice, Ph.D.:  Hi, I am partial to Levi 501's. But for how genes determine traits, well, genes encode for proteins and proteins can form structures or act on other molecules to change or assemble cellular components. This all contributes to the overall makeup of an organism.
MIT in MA (student)

Is adenine, thymine, guanine, and/or cytosine the most basic form of nucleic acids, or are they made from even more basic elements?
Stefan Maas, Ph.D.:  Nucleic acids are the macromolecules made up of nucleotide building blocks. Each of those in turn is made up of one nitrogenous base (adenine (A), thymine (T), guanine (G), and cytosine for DNA; and adenine (A), thymine (T), guanine (G), and uracil (U) for RNA), one ribose sugar molecule (ribose in RNA, deoxy-ribose in DNA) and a phosphate group. So in order to get something that can be called a 'nucleic acid', you would need at least a combination of two of the nucleotide building blocks. Of course, any of these molecular components are composed of atoms and those of sub-atomic particles (such as quarks)..
Chamblee MS in AL (8th grade student)

Are there organelles inside organelles, i mean the different parts that help the specific organelle do its job?
Susan Haynes, Ph.D.:  Many organelles have internal structures that help them do their jobs. For example, mitochondria (the cell's powerhouses) have lots of internal membranes that help to organize the enzymes that generate ATP. Mitochondria even have their own DNA and ribosomes to make some of the proteins they need. Chloroplasts in plants are another example of an organelle with organized internal membranes that help them do their jobs of photosynthesis.
Salk School of Science in NY (6th grade)

Why did the HPV vaccine hurt so bad? I know that shots hurt in general but, that one hurt a lot, and my legs gave out later that night I got the 3rd shot.
Carrie Lucas, Ph.D.:  Thank you for your question about this important vaccine. You can find more information here. cdc.gov Link to external Web site and cancer.gov Link to external Web site
Central in NC (9th grade student)

How were scientists able to determine what organelles were in a cell?
Peggy Weidman, Ph.D.:  Good Question! They started off looking at the insides of cells using something called electron microscopy. By looking at lots of different cells they discovered some structures were present in every cell they looked at and named them organelles. Then they had to figure out what they did for the cell!
New Century Technology High School in AL (teacher)

Hello! :) We were wondering what the nucleus of an atom has in common with the nucleus of a cell?
Douglas Sheeley, Sc.D.:  Great question. After all, taking science classes, and doing science, often involves learning a lot of new words, and when the same one gets used for different things that don't seem to have anything to do with each other, it might seem confusing. What the nucleus of an atom and the nucleus of a cell have in common is the meaning of the word nucleus. We get the word nucleus from a Latin word for the "inner part" or "kernal." Scientists and doctors in western countries often used (and sometimes still do use) Latin words to name things because that was a language that they all had in common from school, no matter what country they were from or language they spoke. So, imagine scientists looking at cells through a microscope and seeing a big spot in the cell that looked like a central core or kernal. Maybe you'd call it a "nucleus." When other scientists were figuring out what atoms were made of, they found that there were relatively large, heavy clusters of protons (and later neutrons) in the center, and light, fast electrons flying around that inner core, or "nucleus." Two different branches of science, same basic idea. Keep trying to connect physics, chemistry, and biology. That's where you have the most fun- at the boundaries between fields.
Salk School of Science in NY (6th grade)

wuts ur fb
Joe Gindhart, Ph.D.: NIGMS Facebook page Link to external Web site
Salk School of Science in NY (6th grade)

What is the most important organelle?
Peter Lyster, Ph.D.:  Hi: That is a very good philosophical question. Before I answer I want to say that not all cells have the same complement of organelles, e.g., bacteria cells do not have nuclei. Also, most parts of living beings are highly optimized over time, meaning that they are perfected by trial and error as the population evolves. So I think that no organism can live without its full complement of organelles: the organelles are all equally important (just like your little brothers and sisters!).
Salk School of Science in NY (6th grade)

Which cells are the reproductive cells ?
Susan Haynes, Ph.D.:  Specialized cells are used for sexual reproduction. The general term for them is gametes, but they are often called different names in different organisms. In mammals, the reproductive cells are called oocytes (or eggs) in females, and sperm in males. In flowering plants, they are called ovules (female) and pollen (male).
Salk School of Science in NY (6th grade)

Do cells have different colors for each type? What colors are they?
Stefan Maas, Ph.D.:  Generally, cells do not have specific colors. However, some types of cells contain high amounts of particular molecules, such as hemoglobin in red blood cells, which gives those cells a dominant color. Others, like melanocytes in the skin, produce a pigment that is a determinant of skin color. Also, please see the answer to question #5.
Webutuck High School in NY (11th grade student)

When was the first "Cell Day"?
Joe Gindhart, Ph.D.:  The first NIGMS Cell Day was in November 2012. This is the second Cell Day. We really like doing this, so i hope there will be more Cell Days in the future!
New Century Technology High School in AL (teacher)

Can osmosis kill a living thing?
Peter Lyster, Ph.D.:  Hi: That's a deep questions, and thanks for that. Actually I think osmosis can kill, but that rarely happens. Firstly I want to remind you that osmosis is when water moves from one place to the other where the density of particles is higher. For example osmosis tends to force water to enter in to a cell from the blood. This is obviously a very important issues since we are all made up of cells and this competition of water is therefore going on all the time. Actually, in cells there is an electric field that competes with osmosis and that keeps us humans in balance. Recently a police officer in Washington died on the job when his osmotic balance failed. This was a tragedy for him and his family. Luckily this is an extremely rare event since humans are a very resilient organism indeed!
Salk School of Science in NY (6th grade)

Is it possible to create fake (or real) organelles/cells?
John Laffan, Ph.D.:  Scientists at the Venter Institute did create a synthetic cell in 2010. It is a synthetic simple bacteria and it can replicate itself. So it is a real cell in a sense but it was made from non living parts. It was a demonstration of a concept and it cost millions, so not really a practical everyday thing.
Salk School of Science in NY (6th grade)

yo is the nucleus the best?
Susan Haynes, Ph.D.:  Best is hard to say - they're all important to keep the cells in your body working right!
Salk School of Science in NY (6th grade)

Does anyone know where the first cell came from?
Peggy Weidman, Ph.D.:  See answer to question 35:It is generally thought that bacteria-like cells (prokaryotes) are the first types of cells found on Earth. They are believed to have appeared about 4 billion years ago. Evidence for the most ancient forms of life are found in fossils called stromatolites. These bacteria were probably chemoautotrophs. That is, they ate chemicals found in the environment.
New Century Technology High School in AL (teacher)

When were cells discovered?
Douglas Sheeley, Sc.D.:  Terrific question. Cells are very small, right? So, it would be hard to see them or understand what they are without some kind of tool that lets you see very small things close up. Enter the microscope! What we think of as a microscope- an arrangement of two lenses that magnifies objects (a compound light microscope) was invented in the Netherlands in the 1500s by people who probably spent most of their time making eyeglasses. A lot of scientists started either making or buying them, and improving them. By the middle of the 1600s, Robert Hooke, a British scientist, published a book describing some of the things he could see through a microscope. Why bring him up? He looked at sections of plants through a microscope and saw what looked like little boxes with walls around them. They reminded him of the little rooms that monks lived in, which were called...cells. That's how we got the word cell in biology. What Hooke saw were plant cells surrounded by cell walls. Other scientists discovered single celled organisms swimming around in pond water, and cells in animals. We've been using bigger and better microscopes ever since, along with lots of other tools, to keep learning more about the many different kinds of cells and how they work.
Webutuck High School in NY (9th grade student)

What kinds of cells do plankton have?
Joe Gindhart, Ph.D.:  Despite my enjoyment of the show SpongeBob SquarePants, plankton is not the core of my expertise. My understanding is that plankton is an ecological zone that contains many types of organisms that float along ocean currents, rather than swimming against them. There are many cool websites with pictures and descriptions of the organisms that inhabit the plankton niche. Thanks for your interest in Cell Day!
Webutuck High School in NY (9th grade student)

What things does the cell membrane let in to the cell and how do these things help it
Richard Okita, Ph.D.:  This is a great question. Cells are living units so they need nutrients to synthesize the big molecules that it needs to function such as energy production or to make proteins, DNA, RNA, and other important molecules and organelles. So the type of things that the cell membrane allows to pass through are amino acids, fatty acids, small sugar molecules. Membranes also allow various small molecules such as drugs or other foreign compounds that may be ingested or absorbed into body. In many cases, the membranes have specific protein molecules that serve as "transporters" or "channels" that select which small molecules can enter into the cell.
Salk School of Science in NY (6th grade)

What causes the visible signs of aging? Doesn't have something to do with the ends of the DNA molecules?
Peggy Weidman, Ph.D.:  Yes, you are right! At the end of each chromosome arm are structures called telomeres. When a cell makes new copies of the chromosomes, the telomeres must be replicated too. With age, however, these telomeres get shorter and shorter.
New Century Technology High School in AL (teacher)

Is there evidence to suggest that there are organelles we don't know about?
Stefan Maas, Ph.D.:  Generally, an organelle is defined as a structure within a cell that has a particular function that is enclosed within its own membrane (such as the nucleus, mitochondrion, lysosome etc.). So of cells from known species, it is unlikely that there will be additional organelles to be discovered, simply because these structures have sizes that are easily detected with standard microscopic techniques.
Salk School of Science in NY (6th grade)

How are genes related to the division of cells
Stefan Maas, Ph.D.:  Genes encode the information to make gene products (such as proteins or nucleic acids). Cell division requires many different gene products to occur and for its regulation. Therefore, many genes are needed to allow a cell to undergo division.
Webutuck High School in SD (9th grade student)

Where did the first cell come from?
Peggy Weidman, Ph.D.:  See answer to this question!
Marion Academy in AL (student)

What do yo believe the most necessary cell organelle is?
Susan Haynes, Ph.D.:  That's hard to say - one of the fascinating things about cells is how all the parts of a cell work together to make sure that it functions correctly! Without the nucleus, you wouldn't have the blueprint and operating instructions for the cell. Even a cell that doesn't have a nucleus (like red blood cells) started out with one and lost it as the cell became more specialized. So the nucleus is critical. But if you didn't have a way to make energy (mitochondria), the cell couldn't function either. And if you didn't have lysosomes, cells would fill up with damaged proteins, and that wouldn't be good.
Salk School of Science in NY (6th grade)

Which cells were probably the first cells on the world
Peggy Weidman, Ph.D.:  See answer to question 35!
Webutuck High School in NY (9th grade student)

Who has been working in your respective field the longest?
Peter Lyster, Ph.D.:  Great question. I want to tell you a story. My hero was a great German mathematician called Carl Friedrich Gauss. He was one of the greatest scientists ever. Early in 1801 someone found a new planet Ceres, but quickly lost it in his telescope. So Gauss invented a model for planetary motion (an ellipse around the sun) and fitted the model to the data (observations) and he was able to rediscover the planet in the sky at the end of 1801. It was a sensation in the news. A great discovery in science. My field is deals with modeling. I have modeled hot gases and cold gases. Some of my colleagues model cells and that is pretty exciting: http://www.nrcam.uchc.edu/ Link to external Web site. So you can see that the first successful modeler could have been Gauss and he passed away 159 years ago! http://en.wikipedia.org/wiki/Carl_Friedrich_Gauss Link to external Web site
New Century Technology High School in AL (teacher)

How do environmental issues affect genes and create mutations?
John Laffan, Ph.D.:  Many environmental agents can directly affect genes. Radiation can cause breaks in DNA and many chemicals can also affect the chromosomes either by directly interacting with the DNA or with the enzymes that maintain or replicate the DNA. Changing the DNA will create mutations; many of the mutations will be detrimental or have no noticeable effect.
Jane Addams Middle School in IL (8th grade student)

How many DNA strands are in one nucleus?
Joe Gindhart, Ph.D.:  The answer to this question depends on the organism and the stage of the cell cycle. Some organisms have only a few chromosomes; for example, fruit flies have four chromosomes. A somatic fruit fly nucleus would have 16 single-stranded pieces of genomic DNA. However, after S phase of mitosis, when DNA replication occurs, there are 32 strands of genomic DNA in the nucleus. A human has 23 chromosomes, but the same concept applies.
Jane Addams Middle School in IL (8th grade student)

Can cells in a person be modified to make a person what they want be or what they want to look like?
Douglas Sheeley, Sc.D.:  Cells, no matter what kind, follow a set of instructions in their genes, or DNA. If you want to modify the way a cell works, you have to change the genes. Scientists have learned a lot about how to do that. By turning a gene on or off, or inserting a gene not normally found in a cell, it is possible to change the way that cell works, or the job it does. Changing a person's cells to make them look different or have different abilities would be hard to do because people are pretty complicated and we don't understand what all the genes are that might affect a specific ability or aspect of our appearance. There are other problems with trying to do this, too. Think of identical twins. They don't usually end up having the same talents or doing the same jobs, but they have the same genes, so that tells us that genes are not the whole story. Good thing! I like that our whole lives are not predictable from just our genes. That bring us to the biggest problem- whether it is even really a good idea to fiddle with our genes in order to engineer people who are better at one thing or another. It's appealing to think that we could eliminate a gene for an inherited disease, but most people agree that we have to be very careful about deciding whether to change people's genes.
Marion Academy in AL (student)

If one parent has all dominant genes and the other has all recessive, would the child look exactly like the parent with the dominant genes?
Joe Gindhart, Ph.D.:  I'm not sure how healthy the "all recessive" parent would be, but I think that the answer is no. First, there is a 50% chance that the child would be a different gender than the "dominant" parent. Second, epigenetic phenomena can change levels of gene expression; that's why identical twins don't look exactly alike. Third and finally, not all genes express standard dominant/recessive relationships; sometimes one "good" copy of a gene is insufficient for the "wild type" phenotype to express itself.
Jane Addams Middle School in IL (8th grade student)

Can you find out about genetic mutations before any immediate signs are found?
Peter Lyster, Ph.D.:  Hi And thanks for the great question. Well, there are mutations that you get from your mother and father and some mutations that may happen to your DNA during your life. It is possible to do some tests before you get born to see if the baby has mutations. It is also possible to do some tests on you during your life. However there are so many opportunities for mutations that it is hard to pinpoint when and where to do the test. It sounds scary but I want you to know it is pretty rare and your body has lots of ways of fixing most mutations.
Jane Addams Middle School in IL (8th grade student)

What is the largest single cell and how big is it?
Joe Gindhart, Ph.D.:  I imagine that the Guinness Book of World Records would list a bird egg as the largest cell, perhaps from an ostrich. However, there are nerve cells that are several feet long, such as nerve cells in our leg, a giraffe neck, or the squid giant axon of the giant squid (imagine that one!). Thanks for your question.
Spencer Middle School in WV (8th grade student)

How are cells living?
Richard Okita, Ph.D.:  Cells are the basic unit of living organisms, they can divide and carry out basic functions that keep organisms alive. The other way to answer your question is that cells are alive because if you restrict oxygen and nutrients they can die.
Jane Addams Middle School in IL (8th grade student)

What does a cell look like as it goes through apoptosis?
Stefan Maas, Ph.D.:  Apoptosis is one of several ways a cell can die. An important characteristic of apoptosis (in contrast to another form of cell death called necrosis) is that within the organism the cells that undergo apoptosis self-digest themselves and are removed without spilling any of the cellular components. As a result, an immune reaction and inflammation are prevented. From the outside (such as through a microscope) a cell undergoing apoptosis will show changes in its morphology, for example membrane blebbing, which involves the break up of the cytoskeleton causing the membrane to bulge outwards.
New Century Technology High School in AL (teacher)

Was there life before cells? From Private Reville
Peggy Weidman, Ph.D.:  Interesting question! It depends on how you define life. Cells are defined as the smallest unit of life that can replicate independently. Before cells evolved, it's believed that some of the basic components that were eventually incorporated into cells existed free in the ocean. See this discussion on the origins of life for more information: http://en.wikipedia.org/wiki/Evolution_of_cells#The_first_cells Link to external Web site
Marion Academy in AL (student)

Could skin cells develop cancer due to a person changing environments often (i.e., moving from country to country and/or state to state.)?
John Laffan, Ph.D.:  Skin cells can develop cancer, which may have been influenced by the indiviual's environment. One (or more) of the person's environments may have contributed more to the skin cancer than others but the changing of environment is probably a smaller contributor.
Spencer Middle School in WV (8th grade student)

What is the most common and least common genetic mutation in humans?
Susan Haynes, Ph.D.:  Although humans mostly have the same DNA sequence, if you look closely enough, we're all different. Some genetic variations are so common (found in more than 1% of people) that they are considered normal variation. Others are extremely rare. In fact, every time scientists determine the DNA sequence of a different person, they find new genetic variations. More information on mutations is available at the Genetics Home Reference (http://ghr.nlm.nih.gov/info=mutations_and_disorders/show/alltopics Link to external Web site).
Jane Addams Middle School in IL (8th grade student)

How fast do skin cells reproduce?
Joe Gindhart, Ph.D.:  The cell cycle of a typical human cell is 24 hours; the length of the cell cycle is constrained by how long it takes the cell to reproduce DNA, build the mitotic spindle, and properly segregate chromosomes to the daughter cells.
Spencer Middle School in WV (8th grade student)

What causes cells to go crazy and cause cancer?
Peggy Weidman, Ph.D.:  A hallmark of cancer cells is uncontrolled growth. This happens when the cell?s normal signals that control cell division don?t work properly, which may be the result of the signals controlling the process as well as an error, or mutation, in the DNA. Researchers are studying another process, cell migration, to better understand how cancer cells spread to other parts of the body.
Jane Addams Middle School in IL (8th grade student)

Information - Moderator Moderator:  The Cell Day chat is coming to a close. We'll take a few more questions.

We think Cell Day should be an annual event like Pi Day!
Joe Gindhart, Ph.D.:  So do we! Perhaps we could have it on Avogadro's Number Day (6:02 on October 23). Thanks again for your support.
New Century Technology High School in AL (teacher)

What is the best way to keep your cells healthy?
Peter Lyster, Ph.D.:  Hi. That is a very important question. It is certainly important to keep your cells healthy since they all add up to make your body. Thus you are only as good as all your cells and bones and chemicals make you. Your body is a system with lots of interconnections and feedback. So your cells depend on lots of things, such as the food you eat, the amount of exercise, your good emotional health. We have lots of wisdom handed down through the generations, e.g., all things in moderation, eat your vegetables, chew your food, don't eat too much salty food or fatty food. If you pay attention to this and look after yourself then you will give your cells the best chance to be healthy.
Swanson Middle School in VA (7th grade student)

What happens is some how a guanine go paired with a thymine or an adenine with a cytosine?
Richard Okita, Ph.D.:  If guanine were to pair with thymine or adenine to cytosone, this would cause significant problems for a cell. Your DNA molecules would not be able to align correctly. It would lead to problems with DNA replication and other cellular functions.
Jane Addams Middle School in IL (8th grade student)

I know that the cell wall and membrane are really similar but what is the main difference?
John Laffan, Ph.D.:  The plant cell wall is composed of cellulose and lignin and it provides a rigid structure. The membranes are composed of lipids and it is very fluid. The both are involved in separating areas and often work together.
Salk School of Science in NY (6th grade student)

How many cells die in a human body each day?
Stefan Maas, Ph.D.:  One can only extrapolate the total number of cells that die each day in the human body. In particular skin cells, blood cells and some additional epithelial cells are those of which the largest number are produced each day and die every day. Overall, there are probably in the order of hundreds of millions to tens of billions of cells that are lost each day.
Spencer Middle School in WV (8th grade student)

Why do some mutations affect some people and not others?
Douglas Sheeley, Sc.D.:  Mutations are usually just a single change in a DNA sequence. DNA is organized into genes, so depending on where a mutation happens, one gene will be affected. Genes "code" or provide the instructions, for proteins, which are the machines that do all the work in cells and organisms. Think of a the gene as a blueprint and a protein as a machine. If you are in 8th grade, you might not have learned yet that it takes 3 nucleotide bases in a gene sequence to code for one amino acid, the basic building blocks of proteins (there are twenty of those). Imagine that one change in a gene sequence changes one of those three base codes. That can have different results- since there is more than one three base code for most of the amino acids, the change might not make any difference. That's a "silent" mutation. If the mutation changes the three base code so that a different amino acid goes in the protein, now you've changed a part going into the machine. Sometimes that might not make a big difference, but sometimes it causes a huge problem, like leaving the battery out of a car- everything else is there, but it's basically useless. An example from biology is the change in hemoglobin, the protein in red blood cells that carries oxygen in your blood. There's a mutation that some people have that protects them from malaria if they have one copy of it (we have two copies of every gene- one from Mom and one from Dad). If they get two copies, all their hemoglobin has that difference, and it sticks together in big clumps, causing their red blood cells to get distorted - they end up shaped like curved sickles- they have sickle cell anemia. So, mutations can affect us in good ways, or bad ways, or not at all. And of course, a really important point is that mutations don't happen in everybody- they are changes that occur spontaneously as "mistakes" when our DNA is copied and end up causing problems or conferring a benefit in the people who they happen to. Those changes then get passed down to their kids.
Jane Addams Middle School in IL (8th grade student)

How has evolution affected the nitrogenous bases of DNA?
Stefan Maas, Ph.D.:  That is a very interesting question; actually, when looking at all of the organisms on earth, from the most 'primitive' bacteria to mammals and humans, it turns out that the genetic code being used (how the genetic information is encoded within DNA) is almost the same. This means that the molecular structure of the DNA building blocks, such as the nitrogenous bases, have changed little throughout evolution. Since these structures are so critical for faithful inheritance of the genetic information and for cells to function, even small changes would dramatically impact any such cell where such a change occurs. Most likely, these changes will be lethal to the cell and therefore not prevail over time. This explains why the bases have not evolved much.
New Century Technology High School in AL (teacher)

Is there a mutation on the human body that are helpful?
Douglas Sheeley, Sc.D.:  Great question. For some background on mutations, look at my answer to question 206, just a few minutes ago. I wrote about a mutation in the protein hemoglobin that is both beneficial and harmful, depending on whether you get one or two copies of that version of the gene. Mutations are like that- they are just a sequence change that often happens just by accident. Our cells copy DNA incredibly fast, and have good ways of checking for mistakes, but sometimes they sneak through. Mutations result in changes in a gene, and then the sequence of the protein that the gene codes for. Differences in genes mean diversity, which is a good thing. Genetic diversity is how species adapt to new environmental influences. Sometimes a mutation is beneficial, sometimes it is harmful, and sometimes there's a trade-off- maybe it helps in one way but hurts in another. Thanks for asking, and thanks for participating in Cell Day!
New Century Technology High School in AL (9th grade student)

What kinds of mutations are not beneficial to humans?
Susan Haynes, Ph.D.:  Although this is still a topic of active study, many geneticists believe that most new mutations are harmful. How harmful depends on what the mutation affects. Mutations that abolish the normal function of a protein can cause lots of problems for people. If the function of the protein is crucial for a cell to survive, then the organism can't survive. Other mutations make the proteins work less effectively, but still function enough so that the person is alive. Even mutations that simply cause production of more or less normal protein can be a problem, because this can throw the cell off balance.
New Century Technology High School in AL (teacher)

Information - Moderator Moderator:  Thank you for making Cell Day a success. We received more than 200 questions. We will post the entire transcript soon.

This page last reviewed on November 2, 2014