Slide 1 of 18 Copyright Pearson Prentice Hall 10-3 Regulating the Cell Cycle

Slide 2 of 18 Copyright Pearson Prentice Hall Cell Cycle Regulators How is the cell cycle regulated?

Slide 3 of Regulating the Cell Cycle Copyright Pearson Prentice Hall Controls on Cell Division One way to control the cell clock:EXTERNAL REGULATION 1. Contact Inhibition

10-3 Regulating the Cell Cycle Slide 4 of 18 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.

Slide 5 of Regulating the Cell Cycle Copyright Pearson Prentice Hall Cell Cycle Regulators The cell cycle is regulated by a specific protein(s). 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.

Slide 6 of Regulating the Cell Cycle Copyright Pearson Prentice Hall A sample of cytoplasm is removed from a cell in mitosis. The sample is injected into a second cell in G 2 of interphase. As a result, the second cell enters mitosis. Cyclins were discovered during a similar experiment to this one. Cell Cycle Regulators

Slide 7 of Regulating the Cell Cycle Copyright Pearson Prentice Hall 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. Ex: Can’t start mitosis unless the DNA has been copied. Cell Cycle Regulators

Slide 8 of Regulating the Cell Cycle 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. Ex: Contact inhibition

10-3 Regulating the Cell Cycle Slide 9 of 18 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?

10-3 Regulating the Cell Cycle Slide 10 of 18 Copyright Pearson Prentice Hall Uncontrolled Cell Growth Cancer cells do not respond to the signals that regulate the growth of most cells. Eg: They ignore both internal and external signals (regulators)

Slide 11 of Regulating the Cell Cycle 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.

Slide 12 of Regulating the Cell Cycle Environmental factors can cause changes to genes (DNA instructions) that regulate the cycle Changes to the P53 gene that is common in almost all cancers Copyright Pearson Prentice Hall

- or - Continue to: Click to Launch: Slide 13 of 18 Copyright Pearson Prentice Hall 10-3

Slide 14 of 18 Copyright Pearson Prentice Hall 10-3 The cell cycle is believed to be controlled by proteins called a.spindles. b.cyclins. c.regulators. d.centrosomes.

Slide 15 of 18 Copyright Pearson Prentice Hall 10-3 Proteins that respond to events inside the cell are called a.internal regulators. b.external regulators. c.cyclins. d.growth factors.

Slide 16 of 18 Copyright Pearson Prentice Hall 10-3 Once a multicellular organism reaches adult size, the cells in its body a.stop dividing. b.grow and divide at different rates, depending on the type. c.have the same life span between cell divisions. d.undergo cell division randomly.

Slide 17 of 18 Copyright Pearson Prentice Hall 10-3 One effect of an internal regulator is that a cell will not begin mitosis until a.it becomes too large. b.the cell’s growth is stimulated. c.it is in physical contact with other cells. d.all its chromosomes have been replicated.

Slide 18 of 18 Copyright Pearson Prentice Hall 10-3 One factor common to almost all cancer cells is a.a lack of cyclin. b.a defect in gene p53. c.exposure to tobacco smoke. d.exposure to radiation.

END OF SECTION