5.3 Regulation of the Cell Cycle

KEY CONCEPTCell cycle regulation is necessary for healthy growth.

5.3 Regulation of the Cell Cycle

Internal factors• kinases change the activity of other molecules by adding

a phosphate group• cyclins –are rapidly made and destroyed at different

points of the cell cycle. This helps cells advance to different stages of the cells cycle.

External factors • cell to cell contact • growth factors which stimulate internal factors that affect

the cell cycle (cell division)

5.3 Regulation of the Cell Cycle

Internal and external factors regulate cell division.

• External factors include physical and chemical signals.• Growth factors are proteins that stimulate cell division.

– Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells.

5.3 Regulation of the Cell Cycle

• Carcinogens are substances known to promote cancer.• Ex. Air pollution, tobacco smoke, mutated genes carried

by viruses.

• Standard cancer treatments typically kill both cancerous and healthy cells.

5.3 Regulation of the Cell Cycle

• Cancer cells do not carry out necessary functions.

• Cancer cells come from normal cells with damage to genes involved in cell-cycle regulation.

5.3 Regulation of the Cell Cycle

Cell division is uncontrolled in cancer.

• Cancer cells form disorganized clumps called tumors-disorganized clumps of cancer cells that do not carry out normal functions

cancer cellbloodstream

normal cell

– Benign tumors remain clustered and can be removed.– Malignant tumors metastasize, or break away, and can

form more tumors.

5.3 Regulation of the Cell Cycle

– a normal feature of healthy organisms– caused by a cell’s production of self-destructive

enzymes

1.occurs indevelopmentof infants

2.Helps rid the

body of

unhealthy cells

webbed fingers

• Apoptosis is programmed cell death.