1. 10-3 Regulating the Cell Cycle
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Cell Cycle Regulators
How is the cell cycle regulated?
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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.
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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.
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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
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6. 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.
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7. Controls on Cell Division
Contact Inhibition
Cells in a petri dish will continue to grow until they come into contact with other cells.
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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
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9. 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.
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10. Uncontrolled Cell Growth
Cancer cells do not respond to the signals that regulate the growth of most cells.
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11. 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.
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12. 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.
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10-3
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10-3
The cell cycle is believed to be controlled by proteins called
spindles.
cyclins.
regulators.
centrosomes.
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10-3
Proteins that respond to events inside the cell are called
internal regulators.
external regulators.
cyclins.
growth factors.
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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.
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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.
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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.
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