1. LEQ: Why is the eukaryotic cell cycle regulated?
Key terms: cyclin, growth factor, kinase
Reading 5.3 (cancer)

2. Activator:
Briefly explain why the daughter cells resulting from mitosis are genetically identical to each other and to the original parent cell.

3. physical contact with cells Cell signaling: Receptors/enzymes
Cells respond to internal and external signals that regulate cell division.
Cell communication:
physical contact with cells
Cell signaling:
Receptors/enzymes
soluble chemical signals:
Growth factors
Survival signals
Image: Epidermal Growth Factor (EGF) and Epidermal Growth Factor Receptor (EGFR)

4. Internal and external factors: Example
Cell adhesion (stops cycle)
Positional information to nucleus
integrins

5. All cells rely on cell signaling to detect and respond to cues in their environment:
Receptor Tyrosine Kinase (RTKs) activation involves binding to a signal (ligand), the joining together and phosphorylation of proteins.
Growth promoting

6. Signaling pathways
Prevent division or,
Promote cell division:
Ras pathways promote cell division by turning on genes/proteins associated with the cell cycle

7. Cdks coordinate passage through checkpoints:
G1/S
Restriction/ enter S
G2/M
Enter M
Spindle/metaphase
Exit M

8. Cyclins activate Cdks
Timing of each phase can be adjusted
Failure/DNA damage can result in cell death.
apoptosis

9. Cell cycles can vary based on stages of development

10. Apoptosis is programmed cell death:
Programmed cell death purges damaged cells to prevent disease and shape development
Apoptosis is programmed cell death:
Initiation of “death” proteins (caspases)
self-destructive enzymes
Results in progressive cell destruction
animation

11. Pair Question:
Suppose a mutation in a Cdk gene causes the Cdk protein to change shape so it spontaneously activates without the aid of cyclins. Predict what would happen to the cell.
Suppose a mutation in a caspase gene causes a Caspase protein to change shape so it spontaneously activates without the aid of a signaling molecule. Predict what would happen to the cell.

12. Competition in a tissue for growth factors “sculpts” a tissue
Loss of “tails”
Finger webbing
webbed fingers

13. Leaf senescence (fall) is programmed cell death!
Leaf development is programmed, seasonal cell growth!

14. Telomere shortening leads to senescence and programmed cell death