Chapter 5- Cell cycle regulation

Question 1

Cell cycle Functional limitations to growth:

Answer 1

• Surface to volume ratio (S/V) - cell division occurs when volume is too large because cells rely on the surface area of their cell membrane for transport of material. Decrease
  in S/V ratio leads to cell division.
• Genome to volume ratio (G/V) - cell division occurs when the volume of the cell is too large to be supported by the limited size of the
  genome. Decrease in G/V ratio leads to cell
  division.

Question 2

Cell specific regulations:

Answer 2

-Cell specific checkpoints - G1 restriction point (checks for favorable conditions to grow, enters G0 phase if unfavorable), end of G2 (checks accuracy of DNA replication and MPF levels), and M checkpoint (during metaphase, checks for chromosomal attachment to spindle
fibers).
- Cyclin-dependent kinases (CDKs) -
phosphorylate certain substrates to signal cell
cycle progression. Activated by cyclin, a
protein that cycles through stages of synthesis and degradation.
- Growth factors - bind to receptors in the
plasma membrane to signal for cell division.
- Density dependent inhibition - halting of cell
division when density of cells is high.
- Anchorage dependence - cells divide only
when attached to an external surface.