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Reasons for Cell Division. Imagine what you would look like if every scratch or blemish on your skin remained and never healed? Cells come from preexisting cells, so throughout your entire life, you will rely on cell division to replace dead or damaged cells in your body.
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Reasons for Cell Division Imagine what you would look like if every scratch or blemish on your skin remained and never healed? Cells come from preexisting cells, so throughout your entire life, you will rely on cell division to replace dead or damaged cells in your body.
I. Healing and Tissue Repair • Cells don’t live forever. Every second, millions of your bodies cells are injured or die. Cells die as the result of damage, or not enough food or oxygen. • Therefore, your body must replace these dead or damaged cells through the process of mitosis and cell division. • Regeneration – is the process of repairing injured cells or making lost body parts. ie: Animals replacing skin cells or even an appendage.
Aging • Research has found that there is a limit to the number of times a cell can divide. Each type of cell has it’s own limit. • Aging occurs because as cells die they are not replaced or they are replaced slowly and injuries can not be repaired. • This results in change of structure and function of major body systems, eventually leading to their breakdown and potential death of the organism. • Examples: Skin wrinkles, bones lose density, immune system is weakened
II. Growth • All growth in multicellular organisms depends on cell division which increases the number of cells. As the number of cells increase so does the size of the organism. • Think about how we all began as a single fertilized egg cell and the number of cell divisions and amount of cell growth that had to take place to get us to the size we are now. • Most cells are small and of relatively constant size. Instead of dividing, why don’t cells simply continue to increase in size?
Reasons: • As a cell grows the volume of cytoplasm increases faster than the surface area of the cell membrane, which is where all essential substances enter and exit the cell. If the cell became to large there would not be enough exchange of materials through the membrane to sustain it. • The distance of the nucleus, (control center) from all other parts of the cell must be kept small so that messages can be relayed efficiently.
Growth Hormones • Plants and animals both have hormones that effect the growth and division of their cells. • Cells communicate with one other using these chemical messengers. • Understanding these hormones in plants are important to scientists working on ways to increase food production. • The effects of the human growth hormone (GH) can be seen when they are produced in abnormal amounts. Low production can result in dwarfism while high production can result in gigantism.
Questions: • Predict what types of cells in your body are likely to be most and least active. Give reasons for your prediction. • Predict which type of cell would respond to changes in the environment most rapidly. Give reasons for your prediction.
Skin cells: The outer layer is made up of dead cells that become twisted and bent out of shape as they dry. Replacing these dead cells is an important function of cell division.
WHITE BLOOD CELLS - some will live for only hours while others last for approximately 4 days. During an infection their lifespan is reduced and typically won’t last more than 72 hrs. This is due to their function where they are the janitors of your blood - constantly cleaning up debris and fighting off invaders. In addition, they are large cells (compared to RBCs and platelets)... their membranes wear down quickly while being squeezed through small tubes (such as capillaries). In this electron micrograph, a human white blood cell is trapping bacterial cells. This type of cell defends the body against pathogens by engulfing them, delivering them to the lysosome of the cells, and destroying them with the help of the lysosomal enzymes.
Bone Loss • During a person's lifetime, the body constantly breaks down old bone (through a process called resorption) and builds up new bone. Any time old bone is broken down faster than new bone is made, net bone loss occurs. Bone loss can lead to low bone density (osteopenia), weakness of the bone, and eventually osteoporosis.
III. Reproduce • One of the most obvious reasons for cell division is for the reproduction of life (new organism). • Mitosis and cell division are the basis for asexual reproduction. There are Two Basic Types of Reproduction: • Asexual reproduction: - the reproduction of bacteria and other unicellular organisms create offspring with identical genetic information. Cells from multicellular organisms also divide asexually by mitosis, except for the cells found in the ovaries and testes (which use meiosis). • Sexual reproduction: – genetic information from two cells or gametes (created by meiosis) is combined to produce a new organism. - these sex cells are produced by meiosis in specialized sex organs such as the ovaries and testes in mammals. ** We will focus on Asexual Reproduction by the process of mitosis right now.
Asexual Reproduction in Bacteria, Protists, Fungi, Plants & Animals Jigsaw Activity: • Using your text, gather information on an assigned type of asexual reproduction. • You will then be the expert who is responsible for teaching the other students in your group about your topic. They in turn, teach you about their assigned type of asexual reproduction until everyone has all the information. Use the provided table to collect your information and then share with your peers.
Jigsaw Groups: Group 1 – Binary Fission Matt, Shali, Emily, Jaryd, Jocelyn, Melissa Group 2 – Budding Brandon, Maegen, Samantha, Justin, Josh, Taylor Heilman Grp 3 – Fragmentation Jordan, Devyn, Taylor Humm, Ivanna, E.izabeth, Anne-Marie Grp 4 - Spore Formation Brayden, Regan, Brendan, Jessica, Tyson Grp 5 - Vegetative Reproduction Kris, Laura, Kate, Mikaela, Parker
BIO 30 • Binge Drinking Affects Brain, Memory Young Brains More Vulnerable Than Adults' • That old joke about going out drinking to kill a few brain cells may not be so funny any more.Young people who binge drink could be risking serious damage to their brains now and increasing memory loss later in adulthood, according to new research. Adolescents may be even more vulnerable to brain damage from excessive drinking than older drinkers.Researchers at Duke University, studied frequent binge exposure to alcohol in rats to compare the effects of binge drinking on younger and older rats. The animals were given doses of alcohol which were comparable to multiple instances of binge drinking in humans."We are not concerned about college students who only drink one or two drinks every now and then. We are concerned about heavy drinkers." lead author Dr. Aaron M. White told Reuters Health. "The alcohol dose was very high because we don't know what is an appropriate dose, so we want to show an effect if one is present.""We believe that the adolescent brain is more vulnerable to the neurotoxic effects of alcohol than the adult brain." he said. Alcohol was found to impair activity in the brain receptors responsible for memory and learning.Later Memory Loss • Researchers gave the adolescent rats alcohol in a binge pattern where they received a lot of alcohol one day, then they had a day off. This was repeated over a 20-day period.After a 20-day break, the rats were tested in mazes to determine their basic motor and memory skills. The "binge drinking" adolescent rats were compared with adult rats that were also given high amounts of alcohol, and to both adult and adolescent rats that were not exposed to binge drinking.There was no difference in test performance between the groups of rats until they were given more alcohol. After a moderate dose of alcohol, the rat exposed to binge drinking during adolescence exhibited memory loss."What we found was that the group that was most affected -- made the most errors -- was the group that had the binge pattern exposure as adolescents," White said. "These rats had a more difficult time finding their way through a maze that they were trained to navigate.""The implications of this study are that teenagers who drink heavily and often may be susceptible to the neurobehavioural effects of alcohol than would adults with similar drinking experiences," Dr David McKinzie, assistant professor at the Indiana University School of Medicine told the BBC News. "Of special concern is the possibility that the effects of early chronic drinking may have long-lasting consequences."The study was published in the July 2000 issue of the journal Alcoholism: Clinical and Experimental Research.
