1. 5.3 Regulation of the Cell Cycle KEY CONCEPT Cell cycle regulation is necessary for healthy growth.

2. 5.3 Regulation of the Cell Cycle The Cell Cycle Control System The sequential events of the cell cycle –Are directed by a distinct cell cycle control system, which is similar to a clock Figure 12.14 Control system G 2 checkpoint M checkpoint G 1 checkpoint G1G1 S G2G2 M

3. 5.3 Regulation of the Cell Cycle The clock has specific checkpoints –Where the cell cycle stops until a go-ahead signal is received G 1 checkpoint G1G1 G1G1 G0G0 (a) If a cell receives a go-ahead signal at the G 1 checkpoint, the cell continues on in the cell cycle. (b) If a cell does not receive a go-ahead signal at the G 1 checkpoint, the cell exits the cell cycle and goes into G 0, a nondividing state. Figure 12.15 A, B

4. 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.(Growth hormone, Erythropoietin.) - Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells.

5. 5.3 Regulation of the Cell Cycle Internal factors are kinases and cyclins enzymes. Kinases: Are enzymes that when activated give a phosphate group to a specific molecule thus affecting its activity. Cyclins: Group of proteins that control kinases, they are easily made and destroyed, therefore controlling the cell cycle.

6. 5.3 Regulation of the Cell Cycle –a normal feature of healthy organisms –caused by a cell’s production of self-destructive enzymes –occurs in development of infants webbed fingers Apoptosis is programmed cell death. Still an unknown process, RESEARCH!!

7. 5.3 Regulation of the Cell Cycle Cell division is uncontrolled in cancer. Cancer cells form disorganized clumps called tumors. cancer cell bloodstream normal cell –Benign tumors remain clustered and can be removed. –Malignant tumors metastasize, or break away, and can form more tumors.

8. 5.3 Regulation of the Cell Cycle Cancer cells do not carry out necessary functions, take out space, blood supply and food. Cancer cells come from normal cells with damage to genes involved in cell-cycle regulation. Oncogenes: Accelerate the cell cycle.

9. 5.3 Regulation of the Cell Cycle Carcinogens are substances known to promote cancer. Standard cancer treatments typically kill both cancerous and healthy cells.