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MED 103- BIOLOGY I > 48. CELL CYCLE CONTROL > Flashcards

48. CELL CYCLE CONTROL Flashcards

1
Q
  1. What is the Cell Cycle controlled by?
A
  • protein complexes
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2
Q
  1. Which 2 subunits compose the protein complexes that control the cell cycle?
A
  1. Cyclin (Cyc)
    - this is a regulatory subunit
  2. Cyclin Depended Kinase (cdk)
    • this is a catalytic subunit
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3
Q
  1. What are Kinases?
A
  • enzymes that inactivate or activate other proteins
  • they do this by Phosphorylation
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4
Q
  1. 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
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5
Q
  1. Which aspect of Cyclin fluctuates in the cell?
A
  • the concentration
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6
Q
  1. 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
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7
Q
  1. The phosphorylation of which factors is necessary for DNA replication?
A
  • G1
  • S
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8
Q
  1. 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
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9
Q
  1. 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
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10
Q
  1. 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
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11
Q
  1. 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
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12
Q
  1. What was the first Cyclin Dependent Kinase to be discovered?
A
  • the Mitosis Promoting Factor (MPF)
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13
Q
  1. What does the Mitosis Promoting Factor consist of?
A
  1. MITOTIC CYCLIN
    • Cyclin A or Cyclin B
  2. CDK-1
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14
Q
  1. What does the Mitotic Promoting Factor (MPF) induce?
A
  • the progression from the G2 phase to the M phase
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15
Q
  1. 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
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16
Q
  1. How does the Mitosis Promoting Factor induce the phosphorylation of the proteins of the Nuclear Lamina?
A
  • it fragments the nuclear envelope
17
Q
  1. What is APC?
A
  • Anaphase Promoting Complex
  • it is an E3 Ubiquitin Ligase
18
Q
  1. How does the Anaphase Promoting Complex take part in Negative Feedback?
A
  • APC inactivates Mitotic Cyclins
    (cyc-A/ cyc-B)
  • it inactivates the Mitosis Promoting Factor (MPF)
    during interphase
19
Q
  1. What reduces the activity of the Mitosis Promoting Factor (MPF)?
A
  • the Proteolysis of the Mitotic Cyclins
  • this happens at the end of Mitosis
20
Q
  1. What fluctuates during the Cell Cycle?
A
  • the activity of Cyclins and Cyclin Dependent
    Kinases
21
Q
  1. What are the 6 roles that the Mitosis Promoting Factor plays in the Cell Cycle Regulation in Mitosis?
A
  1. Chromosomal Condensation
  2. Nuclear Envelope Degradation
  3. Mitotic Spindle Formation
  4. Chromosome Migration of Opposite Poles
  5. Organelle Reformation
  6. Cytokinesis

NB:
- the MPF adds phosphate groups to other
enzymes

22
Q
  1. What are the 4 ways in which the Cell Cycle is regulated during Interphase?
A
  1. Mitogens
  2. Expression of Early Response Genes
  3. Activation of G1 Cyclin-Cdk Activity
  4. Transcription of genes for DNA Synthesis
23
Q
  1. What is meant by the term “Mitogens”?
A
  • these are the growth factors
  • they express early response genes
  • they help the cell to progress from the G Phase
    to the S Phase
24
Q
  1. What is meant by the Expression of Early Response Genes?
A
  1. G1 cyclins and Cyclin Dependent Kinases
    • cyc-D
    • cyc-E
    • cdk 2,4 and 6
  2. Transcription Factors
    • c-fos
    • c-jun
    • NB: E2F
25
Q
  1. What are Transcription Factors responsible for?
A
  • they are responsible for the transcription of
    genes
  • these genes are required for DNA replication
  • they play a large roles with regards to S Phase
    genes
    (EG: DNA Polymerase)
26
Q
  1. What is meant by the Transcription of genes for DNA Synthesis?
A

IF THE MITOGEN IS REMOVED:
- reduction in the cyclin-cdk levels
- the cell does not pass through the restriction
point (R)
- the cell does not replicate

27
Q
  1. What are 5 G1 Cyclin-cdks?
A
  1. cyc-D
  2. cyc- E
  3. cdk-2
  4. cdk-4
  5. cdk-6
28
Q
  1. What are 2 S Phase Cyclins-cdks?
A
  1. cyc-A
  2. cdk-2
    (this is required for DNA replication)
29
Q
  1. What are 3 Mitotic Cyclin-cdks?
A
  1. cyc-A
  2. cyc-B
  3. cdk-1
    (this is an MPF)
30
Q
  1. What are the Cell Cycle Progression and the Cell Division driven by?
A
  • they are driven by sequential activation
  • they are driven by the subsequent inactivation of
    cyclins and the cyclin dependent kinases
31
Q
  1. Which three molecules make up the Cell Cycle Control System?
A
  1. Cyclins
  2. Cyclin Dependent Kinases
  3. Tumour Suppressor Genes

MED 103- BIOLOGY I (53 decks)

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