The cell cycle

Question 1

What is the cell cycle?

Answer 1

Highly ordered sequence of events that takes place in a cell, resulting in cell division + formation of 2 genetically identical daughter cells

Question 2

What are the 2 main phases in cell cycle of eukaryotic cells?

Answer 2

• Interphase (longest phase of cycle)
• Mitotic (division) phase

The interphase is the stage of the cycle between divisions

Question 3

What is the interphase?

Answer 3

Cells don’t continuously divide in this phase - they have long periods of growth + normal working between divisions

Cell spends majority of time here

Cell carries out all major functions (e.g. producing enzymes/hormones) whilst actively prepping for cell division

Question 4

What are the 3 stages making up the interphase?

Answer 4

• G1: First growth phase
• S: Synthesis phase
• G2: Second growth phase

(in order)

Question 5

What happens during interphase?

Answer 5

• DNA replicated + checked for errors in nucleus. Then protein synthesis occurs in cytoplasm
• Mitochondria grow + divide, increasing in number in cytoplasm
• Chloroplasts grow + divide (in plant + algal cell cytoplasm)
• Normal metabolic processes of cells occur (including cell respiration)

Question 6

What happens in G0 phase?

Answer 6

Cell leaves cycle temporarily/permenantly due to damaged DNA in cell, differentiation, or aging

Question 7

What happens in the G1 phase (first growth)?

Answer 7

Proteins from synthesised organelles are produced + organelles replicate. Cell increases in size

Question 8

What happens in the S phase (synthesis)?

Answer 8

DNA is replicated in nucleus

Question 9

What happens in G2 phase (second growth)?

Answer 9

Cell continues to increase in size, energy stores increase, + duplicated DNA is checked for errors

Question 10

What happens in mitotic phase?

Answer 10

Period of cell division

Question 11

What are the 2 stages of cell division and their roles?

Answer 11

Mitosis - divides nucleus
Cytokinesis - cytoplasm divides + 2 cells produced

Question 12

What is the order of the cell cycle?

Answer 12

G0, G1, S, G2, Mitotic phase

Question 13

Why does damaged DNA in cell cause cell to leave cycle?

Answer 13

DNA no longer viable + cant divide. Cell enters permanent arrest

Question 14

Why does differentiation cause cell to leave cycle?

Answer 14

It becomes specialised to carry out specific function so cant divide again

Question 15

Why does aging make cell leave cycle?

Answer 15

Number of senescent cells increase

These cells are linked with diseases like arthritis + cancer