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Dynamic Cell > Cell cycle > Flashcards

Cell cycle Flashcards

1
Q

what is the cell cycle?

A

repeated process
cell duplicates itself
produces 2 daughter cells

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2
Q

why study the cell cycle?

A

to understand over-replication in some cells e.g. cancer

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3
Q

loss of cell cycle control

  • regulators
  • leads to…?
A

TSGs
proto-oncogenes

cancer

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4
Q

cell cycle

- 4 main events

A
  1. cell growth
    = duplicate cytoplasmic components
  2. chromosome duplication
  3. chromosome segregation
  4. cytoplasmic segregation
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5
Q

cell cycle

- 5 potential phases

A 
G1
(G0 - cells leave cell cycle + become quiescent)
S
G2
M
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6
Q

cell cycle

- times

A

vary

intestinal cell ~12hrs

human liver cell ~1yr

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7
Q

M phase stages

A 
prophase
pro-metaphase
metaphase
anaphase
telophase
cytokinesis
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8
Q

prophase

pro-metaphase

A

chromosome starts condensing
centrosomes assemble at poles

nuclear membrane break down
spindle fibres start attaching

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9
Q

metaphase

anaphase

A

chromosomes align along equator
attach to MTs of mitotic spindle

segregation
- sister chromatids pulled apart by mitotic spindle to poles

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10
Q

telophase

A

chromatids de-condense

nucelar membrane forms around each set of chromosomes

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11
Q

checkpoints

- purpose

A

stop cell cycle if detect problem in external or internal enviro

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12
Q

3 checkpoints

A

start

G2/M

metaphase/anaphase transition

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13
Q

start checkpoint

  • what does it check?
  • what would happen without it?
A

is enviro favourable?

lack of nutrients

  • > inappropriate cell proliferation
  • > cell death/tumours
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14
Q

G2/M checkpoint

  • what does it check?
  • what would happen without it?
A

is all DNA replicated?
is enviro favourable?

division w/out complete DNA replication

  • > daughter cells lack full complement of chromosomes (aneuploidy)
  • > cell death/cancer
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15
Q

metaphase/anaphase transition

  • what does it check?
  • what would happen without it?
A

are all chromosomes attached to spindle?

division w/ incomplete chromosome attachment

  • > uneven amounts of DNA in daughter cells (aneuploidy)
  • > cell death/cancer
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16
Q

checkpoint regulation

A

cyclins
- activate CDKs via binding

CDKs
- phosphorylate target proteins

17
Q

4 major cyclin-cdk complexes

A

G1-Cdk
G1/S-Cdk
S-Cdk
M-Cdk

18
Q

6 mechanisms that regulate Cdk

A 
transcription 
phosphorylation 
inhibition 
degradation 
localisation 
feedback
19
Q

Cdk levels vs cyclin levels in cell cycle

A

Cdk
- don’t change

Cyclins

  • go up or down
  • > controls activation of Cdks
20
Q

regulation of gene transcription

  • G1-cyclin levels
  • G1/S-cyclin levels
A

increase in G1
high until end of M
decrease to low

increases start of G1
decreases end of G1

21
Q

APC/C

A

initiates cell progression through metaphase-anaphase checkpoint

22
Q

regulation of gene transcription

  • S-cyclin levels
  • M-cyclin levels
A

increases start checkpoint
high levels for half G1, S, G2, half M
decreases metaphase-anaphase transition

increases G2
decreases metaphase-anaphase

23
Q

protein phosphorylation

A

P group covalently added to a protein
via kinase

-> can activate or inhibit

24
Q

binding of inhibitory proteins

A

inhibitory proteins bind to cyclin-Cdk complexes

= inactive

25
Q

targeted proteolysis

A

degrading a protein by hydrolysis at 1 or more of its peptide bonds

ubiquitination tags proteins for degradation by
via proteasome

26
Q

ubiquitination

A

ubiquitin added by ubiquitin ligase
-> deactivates cyclin-Cdk complex

-> cyclin degraded at proteasome
+ Cdk remains inactive

27
Q

localisation

A

proteins:
attached to membrane
free in cytoplasm
contained in nucleus

proteins can only regulate each other when they come into contact

28
Q

feedback loops

A

1 -> 2 -> 3

protein 3 can feedback and up regulate protein 1

29
Q

types of feedback

A

positive
= self-promoting

negative
= self-limiting

Dynamic Cell (15 decks)

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