6.1 Cell cycle

Question 1

What is Interphase:

Answer 1

active phase where cells carry out all if their major functions such as production of enzymes whilst actively preparing for cell division
–> most time is spent in this phase

Question 2

What occurs during interphase:

Answer 2

• DNA is replicated and checked for errors in nucleus
• protein synthesis occurs in cytoplasm
• mitochondria grow and divide, increasing in number in the cytoplasm
• chloroplasts grow and divide in plant and algal cell cytoplasm, increasing in number
• normal metabolic processes of cells occur
  (some, including cell respiration, also occur throughout cell division)

Question 3

3 stages to interphase

Answer 3

G1- First growth phase: proteins from which organelles are synthesised, are produced and organelles replicate. The cell increases in size
S- Synthesis phase: DNA is replicated in the nucleus
G2- Second growth phase: cell continues to increase in size, energy stores are increased and the duplicated DNA is checked for errors

Question 4

What is the mitotic phase

Answer 4

period of cell division, involving 2 stages:
mitosis & cytokinesis

Question 5

Why might a cell leave the cell cycle?

Answer 5

Phase when cells leave the cell cycle either temporarily or permanently because:

The cell has differentiated and is no longer able to divide
The DNA of the cell is damaged so the cell is no longer viable and therefore becomes senescent.
Age. The number of senescent cells increases with age and has been linked with age related diseases.

Question 6

G0 phase

Answer 6

when cell leaves the cycle, either temporarily or permanently. Due to:
- Differentiation: specialised cell cannot divide any more and will carry out it’s function indefinitely)
- DNA is damaged: can no longer divide and enters a period of permanent cell arrest (senescent: growing old)
-Age increase= no of cells increases= growing no of senescent cells= more likelihood of disease such as cancer

Question 7

What are checkpoints

Answer 7

control mechanisms of cell cycle:
- monitor and verify if processes at each phase have been accurately completely

Question 8

G1 checkpoint

Answer 8

At end of G1, before S phase:
Cell size
nutrients
growth factors
DNA damage

If requirements aren’t satisfied, it enters G0

Question 9

G2 checkpoint

Answer 9

End of G2 phase, before mitotic phase:
Cell size
DNA replication (without error)
DNA damage

Question 10

Spindle assembly checkpoint

Answer 10

chromosome attachment to spindle