48. CELL CYCLE CONTROL Flashcards
1
Q
- What is the Cell Cycle controlled by?
A
- protein complexes
2
Q
- Which 2 subunits compose the protein complexes that control the cell cycle?
A
- Cyclin (Cyc)
- this is a regulatory subunit - Cyclin Depended Kinase (cdk)
- this is a catalytic subunit
3
Q
- What are Kinases?
A
- enzymes that inactivate or activate other proteins
- they do this by Phosphorylation
4
Q
- What are Cyclin Dependent Kinases (cdk)?
A
- they are present at a constant concentration in
the cell - they are inactive most of the time
- they become activated by binding to a particular
cyclin
5
Q
- Which aspect of Cyclin fluctuates in the cell?
A
- the concentration
6
Q
- What is the active form of Cyclin Dependent Kinases (cyc-cdk) responsible for?
A
- phosphorylation of various proteins
- this can lead to protein activation or inactivation
7
Q
- The phosphorylation of which factors is necessary for DNA replication?
A
- G1
- S
8
Q
- What regulates the activity of Cyclin Dependent Kinases (cdks)?
A
- they are regulated by the degradation of Cyclins
- the proteasomes degrade the cyclins
- these cyclins can be ubiquitinated through
different enzymes
9
Q
- What is a Proteasome?
A
- they are giant protein complexes
- they bind to protein molecules
- most specifically short lived proteins
- they also bind to incorrectly folded proteins
- they degrade these proteins
- this is known as Proteolysis
10
Q
- Why is the tight regulation of Cyclin Dependent Kinases (cdks) very important?
A
- there is a loss of cell cycle control
- this can lead to unregulated cell proliferation
- this results in Carcinogenesis
11
Q
- What is the name given to the signal that sends cells into Mitosis?
A
- MPF
- Mitosis Promoting Factor
- it is also called the Maturation Promoting Factor
12
Q
- What was the first Cyclin Dependent Kinase to be discovered?
A
- the Mitosis Promoting Factor (MPF)
13
Q
- What does the Mitosis Promoting Factor consist of?
A
- MITOTIC CYCLIN
- Cyclin A or Cyclin B
- CDK-1
14
Q
- What does the Mitotic Promoting Factor (MPF) induce?
A
- the progression from the G2 phase to the M phase
15
Q
- How does the Mitosis Promoting Factor induce the progression from the G2 Phase to the M Phase?
A
- through the phosphorylation and inactivation of
the Anaphase Promoting Complex (APC) - this is an E3 Ubiquitin Ligase
- it targets the S and M cyclins for Degradation