Cell Day Frequently Asked Questions

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Cell Day Participant FAQs

As part of its commitment to encouraging future generations of scientists, NIGMS will host an interactive Web chatroom about the cell and careers in research for high school students.

Cells are the smallest form of life—the functional and structural units of all living things. Your body contains trillions of cells, organized into more than 200 major types. Different cell types are each customized for a particular role. NIGMS is keenly interested in cell biology because knowledge of the inner workings of cells underpins our understanding of health and disease.

Cell Day is sponsored by NIGMS, which is part of the National Institutes of Health, a component of the U.S. Department of Health and Human Services. NIGMS' mission is to support research that increases understanding of life processes and lays the foundation for advances in disease diagnosis, treatment and prevention.

The chatroom will be open from 10:00 a.m. - 3:00 p.m. ET on Thursday, November 3, 2016.

There are plenty of suggested background materials to read before the chatroom opens. Visit the Cell Day Classroom Resources page to learn more.

NIGMS scientists will be on hand to field questions from teachers and students on cell biology and careers in research. High school students, educators and members of the public can ask questions. You must be at least 13 years of age or have the permission of your parent/guardian to participate.

Since the chatroom is Web-based, a computer with a browser with JavaScript enabled and an Internet connection are required. On a PC, the chatroom is compatible with relatively recent versions (within the last 24 months) of the following browsers: Internet Explorer, Firefox, and Safari. On a MAC, it's compatible with recent versions of Safari and Firefox.

We will make every effort to answer questions in a timely fashion. However, we are expecting a very high volume of questions throughout the day. Please be patient, and remember that you can always check the transcript if you do not see your response posted during your class period.

Yes! A transcript will be available shortly after the chat is over. The transcript will be fully searchable. You can either search for answers by a certain expert or search for particular keywords.

If you experience technical problems during the chatroom, please report them to websupport@nigms.nih.gov.

The smallest cell is probably a bacterial cell. Currently, a type of bacteria called mycoplasma (200-300 nanometers in diameter) are thought to be the smallest cells. But, recent research has identified potentially even smaller cells, like the bacterium Peligiabacter and the archaeon 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.

Three options:

  1. Sperm – diameter of 1-3 micrometers, but its tail is 50 micrometers.
  2. Cerebellum granule cell, which play a key role in the sense of smell – diameter of 4-10 micrometers.
  3. The red blood cell – diameter of 4-8 micrometers.

By volume, the largest cell is an ostrich egg. But by length, nerve cells win. There are nerve cells that are several feet long, such as nerve cells in our leg, a giraffe neck or the giant axon of the giant squid (imagine that one!).

There are about 200 cell types and about 30 trillion cells in the human body. That does not include bacteria, fungus and mites that live on the body.

The winner is bound to be a colony of genetically identical, physically connected clones. One possibility is a grove of aspen trees in Utah known as "Pando," which is projected to weigh about 6 million kg. Another contender is a fungus in eastern Oregon. Nicknamed the "Humongous Fungus," this organism covers almost 9 square kilometers, with most of its bulk underground.

Yes! Blueberries are blue, carrots are orange, most plants are green, mustard is yellow, the cells of our retina are black, eggplants are purple, all because of pigments that are present in those cells. Many of the pigments used to dye clothing are isolated from plant and animal sources.

In a living cell, the nucleus is almost completely transparent and colorless. You can't really see it unless you know what to look for! When scientists take photographs of cells in the microscope, they usually treat the cells first with a dye that makes the nucleus blue or purplish blue. Because of this, the nucleus in most cell images is also blue.

Stem cells can be divided into two major categories—embryonic stem cells and adult stem cells. Embryonic stem cells can differentiate into any cell in the body. Adult stem cells, which are present in tissues throughout the body, have more limited capabilities. They can only differentiate into cell types specific to the tissue in which they are located, whether that is skin, blood, muscle, teeth, brain, liver, heart or other tissue. Their purpose is to supply new cells to replace those lost by disease or injury. Adult stem cells can be extracted for use in biological research and, hopefully in the future, for the development of therapies.

Robert Hooke, a British scientist, coined the term "cell" in 1665 after looking at cork tissue through a microscope. What he saw looked like little boxes with walls around them. They reminded him of the small rooms that monks lived in, which were called...cells.

Some toxins produced by bacteria create a channel in the cell's membrane. This channel can either be fatal itself—by allowing ions, water and small molecules to leak out of the cell—or can serve as a portal through which a bacterium injects a toxic protein into the cell. Other toxins can bind to cell surface receptors and hitch a ride into the cell with the receptor. Toxins such as dioxin are small molecules that can pass into the cell membrane because they dissolve in the lipid layer of the membrane.

Some biological processes need to be isolated or separated from other reactions so compartmentalization is important. Some reactions require starting material available only in specific intracellular locations. DNA transcription, for example, takes place in the nucleus where DNA is located while translation or protein synthesis takes place in the ribosomes where all the required proteins and nucleic acids are found.

There are lots of mutagenic substances (like cigarette smoke and ultraviolet radiation) that increase the mutation rate. But mutations also happen naturally during the process of DNA replication. Each of your cells has about 6.4 billion base pairs of DNA that need to be copied every time a cell divides. The replication machinery is very accurate but even if it only made one mistake in a billion, the next generation cell would have six to seven mistakes (it is actually a little better than that).

Yes, sometimes. For example, there was a mutation that allowed people to digest milk even into adulthood. Because it was helpful for survival, this mutation is now present in about 80 percent of people of European descent. 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.

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.

If we only think about mammals, we know that the gestation period (how long a mother is pregnant) varies a lot among species. Mice are born after about three weeks, but elephants take over a year.

Some cells stop dividing when they fully differentiate (like nerve cells) and some cells keep reproducing over your entire life (like skin cells).

It depends on the type of cell. Cells in your small intestine last only 2-4 days. Skin cells last 10-30 days. Sperm cells last two months. Red blood cells last 70-140 days (about four months). Egg cells, and some cells in the brain and eye last your entire lifetime. [Reference: http://book.bionumbers.org/how-quickly-do-different-cells-in-the-body-replace-themselves, which draws its data from http://bionumbers.hms.harvard.edu]

There are two main ways cells can die. Apoptosis, also called programmed cell death, is a normal part of development (it sculpts our fingers and toes and fine-tunes our brains). Necrosis is not normal and results from a sudden traumatic injury, infection or exposure to a toxic chemical.

Viruses 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 single-celled microorganisms that can live and reproduce on their own (they are small but larger than viruses). Not all viruses cause disease. Neither do all bacteria cause disease—in fact, many bacteria are essential to our health! Check out https://biobeat.nigms.nih.gov/2015/04/our-microbial-menagerie/ or do a search on "microbiome" to learn more about this fascinating area of research.

Scientists do not have a complete inventory of the number of cells, prokaryotic or eukaryotic, in our bodies. The numbers they have are estimates. They do know that bacterial cells are many times smaller than eukaryotic cells. So in terms of absolute numbers, there are many more prokaryotes, but they make up less than 3 percent of a person's body mass.

Some viruses attack cells by hijacking normal cell membrane structures and processes. Some may bind to membrane patches, which are rich in membrane fats called cholesterol and sphingolipids. They are then taken up by endocytosis into the cell. The membrane surrounds the virus and engulfs it.

Cancer is a very complicated disease that scientists have been studying for some time. Cancer can involve many different mutations on different genes, and different organs can have their own forms of cancer. The good news is that scientists have made tremendous progress in treating cancer. They have also developed some promising new therapies to treat specific cancers without some of the side effects of chemotherapy. For more information on cancer, go the NIH's National Cancer Institute website.