10-3 Regulating the Cell Cycle Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Cycle Regulators How is the cell cycle regulated? Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Cycle Regulators Cell Cycle Regulators The cell cycle is regulated by a specific protein called cyclin. The amount of this protein in the cell rises and falls in time with the cell cycle. Scientists called this protein cyclin because it seemed to regulate the cell cycle. Cyclins regulate the timing of the cell cycle in eukaryotic cells. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Cycle Regulators Internal Regulators  allow the cell cycle to proceed only when certain processes have happened inside the cell. They are often triggered by external factors including cyclins and kinases. Kinases change the activity of other molecules by adding a phosphate group. Cyclins are rapidly made and destroyed at different points in the cell cycle. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Cycle Regulators External Regulators  Proteins that respond to events outside the cell are called external regulators. direct cells to speed up or slow down the cell cycle. Include cell to cell contact and other physical signals; chemical signals to stimulate cell growth or cell division Copyright Pearson Prentice Hall

Controls on Cell Division Experiments show that normal cells will reproduce until they come into contact with other cells. When cells come into contact with other cells, they respond by not growing. This demonstrates that controls on cell growth and division can be turned on and off. 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

Copyright Pearson Prentice Hall Cell Cycle Regulators Apoptosis is programmed cell death. Plays a role in normal development caused by a cell’s production of self-destructive enzymes to rid the body of unhealthy cells Examples- Carves away webbing between fingers and toes after sunburn, this form of cell death peels away damaged skin webbed fingers Copyright Pearson Prentice Hall 8

Uncontrolled Cell Growth Carcinogens are substances known to promote cancer. Cancer is a disorder in which some of the body's own cells lose the ability to control growth. Standard cancer treatments typically kill both cancerous and healthy cells. Copyright Pearson Prentice Hall

Uncontrolled Cell Growth Cancer cells do not respond to the signals that regulate the growth of most cells. Copyright Pearson Prentice Hall

Uncontrolled Cell Growth Cancer cells divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues. They continue to grow despite cell-to-cell contact or lack of growth factors. Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death. Copyright Pearson Prentice Hall

Uncontrolled Cell Growth Malignant cells break away from tumors and form new tumors. Benign cells stay clumped together and are more easily removed. Standard cancer treatments typically kill both cancerous and healthy cells. Copyright Pearson Prentice Hall 12

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

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