Copyright Pearson Prentice Hall Biology Copyright Pearson Prentice Hall

10-3 Regulating the Cell Cycle 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 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. 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 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 a result, the second cell enters mitosis. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Cycle Regulators Internal Regulators  Proteins that respond to events inside the cell are called internal regulators. 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  Proteins that respond to events outside the cell are called external regulators. External regulators direct cells to speed up or slow down the cell cycle. Copyright Pearson Prentice Hall

Uncontrolled Cell Growth Cancer is a disorder in which some of the body's own cells lose the ability to control growth. How are cancer cells different from other 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. 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

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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