Revised notes: Cyclin-dependant kinases

Question 1

What are Cdks?

Answer 1

Cyclin-dependant Kinases that act on other proteins involved in the cell cycle

Question 2

How are Cdks activated? (3)

Answer 2

1. Cyclin binds to CDK
2. This allows phosphorylation of CDK by Cdk activating kinase (Cak)
3. Cdk now active and can now phosphorylate its substrate

Question 3

Chain of Cdk activation in the cell cycle

Answer 3

1. Cyclin D is first synthesised to activate Cdk4/6 in order for cells to pass the R point (G1)
2. Cyclin E levels increase and activates Cdk2 (G1)
3. E-Cdk2 activates cyclin A-Cdk2 which is required for DNA replication in S phase (S)
4. Cyclin A-Cdk2 ensures Cyclin B-Cdk1 becomes active to allow cells to progress to M phase (G2)

Question 4

What are the 2 classes of Cdk inhibitors?

Answer 4

• Inhibitor of Cdk4 (INK4)

- Cyclin dependant kinase inhibitor proteins (CIP)