10-3 Regulating the Cell Cycle Copyright Pearson Prentice Hall

Controls on Cell Division Contact Inhibition Cells in a petri dish will continue to grow until they come into contact with other cells. Copyright Pearson Prentice Hall

Controls on Cell Division Contact inhibition – Cells stop growing when in contact with other cells Cell growth can be turned on and off by internal and external regulators. Once cells reach adult stage they grow and divide at different rates depending on cell type. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Cycle Regulators Cell Cycle Regulators Cell cycle is regulated by a specific protein called cyclin. amount of protein rises and falls in time with the cell cycle Cyclin directs the cell to go into mitosis. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Cycle Regulators Cyclins were discovered during a similar experiment to this one. The timing of the cell cycle is regulated by cyclins. When cytoplasm from a cell in mitosis is injected into another cell, the second cell enters into mitosis. The reason for this effect is a protein called cyclin, which triggers cell division. A sample of cytoplasm is removed from a cell in mitosis. The sample is injected into a second cell in G2 of interphase. As result, the second cell enters mitosis. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Cycle Regulators Internal Regulators  Internal regulators - Proteins that respond to events inside the cell Internal regulators allow the cell cycle to proceed only when certain processes have happened inside the cell. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Cycle Regulators External Regulators  External Regulators - proteins that respond to events outside the cell. External regulators direct cells to speed up or slow down the cell cycle. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall What is the Life span of a human cell? It depends on what cell it is. e.g. blood cell, skin cell, stomach tissue cell Recent studies have shown that few cells live as long as the individual they belong to without renewal. A majority, if not all, the cells making up the cerebral cortex belong to this small group. The life span of some other human cells are as follows: Copyright Pearson Prentice Hall

Lifespan of select human cells: Platelets -- 10 days Skin epidermal cells -- 2 - 4 weeks Lymphocytes -- 2 months - a year Red blood cells -- 4 months Stomach lining cells -- 2 days Macrophages -- months - years Endothelial cells -- months - years Pancreas cells -- 1 year or more Bone Cells -- 25 - 30 years  Cell Type – Lifespan Granulocytes -- 10 hours to 3 days Stomach lining cells -- 2 days Sperm cells -- 2-3 days Colon cells -- 3-4 days Epithelia of small intestine -- 1 week or less Copyright Pearson Prentice Hall

Uncontrolled Cell Growth Uncontrolled Cell Growth xxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Cancer is a disorder in which some of the body's own cells lose the ability to control growth. Cancer cells divide uncontrollably form masses of cells called tumors Tumors can damage surrounding tissues Metastatic cancer cell – cell that breaks loose from tumor and spreads throughout the body Cancer is usually caused by a defect in gene p53 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-3 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-3 The cell cycle is believed to be controlled by proteins called spindles. cyclins. regulators. centrosomes. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-3 Proteins that respond to events inside the cell are called internal regulators. external regulators. cyclins. growth factors. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-3 Once a multicellular organism reaches adult size, the cells in its body stop dividing. grow and divide at different rates, depending on the type. have the same life span between cell divisions. undergo cell division randomly. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-3 One effect of an internal regulator is that a cell will not begin mitosis until it becomes too large. the cell’s growth is stimulated. it is in physical contact with other cells. all its chromosomes have been replicated. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-3 One factor common to almost all cancer cells is a lack of cyclin. a defect in gene p53. exposure to tobacco smoke. exposure to radiation. Copyright Pearson Prentice Hall

END OF SECTION