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Biology of the Cell > Unit 3: Cell Cycle (Lectures 1-2) > Flashcards

Unit 3: Cell Cycle (Lectures 1-2) Flashcards

1
Q

Why do cells divide (3) ?

A
  • To repair tissue damage
  • Reproduction
  • Growth
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2
Q

Why are larger cells less effective (3) ?

A
  • As they have a decreased ability to absorb nutrients and remove waste
  • Cannot produce enough RNA to function properly
  • Less likely to respond to extracellular siganalling
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3
Q

What is proliferation ?

A

A rapid increase in the number of amount of something

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4
Q

What does uncontrolled proliferation lead to ?

A

Cancer

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5
Q

What are 2 methods of regulating proliferation ?

A
  • Extracellular signals
  • Intracellular regulatory proteins
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6
Q

What triggers cell division ?

A

Mitogens

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7
Q

What is a mitogen ?

A

A chemical substance which encourages a cell to commence cell division, leading to mitosis

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8
Q

How do mitogens work ?

A

By binding to a cell surface receptor to trigger intracellular signalling. This promotes entry into the cell cycle

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9
Q

What type of receptor is a mitogen ?

A

An enzyme linked receptor

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10
Q

What pathway is activated by receptor kinase ?

A

Mitogen activated protein kinase pathway (MAP)

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11
Q

What is a telomere ?

A

A specialised nucleotide sequence at the end of each chromosome

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12
Q

What happens when telomeres get too short ?

A

Cell senescence

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13
Q

Every time a cell divides what happens to the telomeres ?

A

The telomere is not fully copied

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14
Q

What are the 3 parts of interphase ?

A
  • G1
  • S Phase
  • G2
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15
Q

What is the duration of a cell cycle ?

A

24 hours

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16
Q

What is G0 (2) ?

A
  • Resting phase
  • Cells are not dividing or preparing to divide
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17
Q

What do cells come across in the middle of G1 and what does this do ?

A

The G1 restriction checkpoint, this is the point of no return and checks DNA integrity

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18
Q

What must cells inactivate in order to go past the G1 checkpoint ?

A

Retinoblastoma tumor supressor protein (Rb)

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19
Q

What is the job of Rb?

A

It is a transcriptional repressor and blocks the function of E2F

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20
Q

What is the job of E2F?

A

It is a transcription factor that stimulates the expression of genes needed for the cell cycle

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21
Q

What controls the activity of Rb?

A

Cyclins

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22
Q

What cyclin is used in G1?

A

Cyclin D

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23
Q

What cyclin is used in the transition from G1 to S ?

A

Cyclin E

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24
Q

What cyclin is used in S?

A

Cyclin A

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25
What cyclin is used in G2 and M?
Cyclin B
26
What does CDK stand for ?
Cyclin dependant kinases
27
What CKDs bind to cyclin D ?
- CDK4 - CDK6
28
What CDK binds to cyclin E and cyclin A ?
CDK2
29
What CDK binds to cyclin B ?
CDK1
30
When are CDKs active ?
When bound to a cyclin
31
What happens in step 1 of the cell cycle- early G1 (3) ?
- Mitogens activate the intracellular signalling cascade - Cyclin D-CDK4 phosphorylates and partially inactivates Rb - E2F stimulates the expression of genes such as cyclin E
32
What happens in step 2 of the cell cycle- late G1 ?
- Cyclin E-CDK2 phosphorylates Rb for a second time - Rb is fully inactivated and cannot bind to E2F - E2F promotes the expression of genes needed for the S phase
33
What happens at the G1 checkpoint ?
- DNA is checked that there is no damage - DNA that is damaged or mutated will not be copied - If damage is not repaired then apoptosis will occur
34
What protein is a crucial component of the G1 checkpoint ?
p53
35
How long does the S phase take ?
10-12 hours (half cell cycle)
36
What is the aim of the S phase ?
- To accurately copy DNA - Avoid mutations - DNA must be distributed so that daughter cells have an identical genome
37
How long in m in chromosomal DNA ?
2m long
38
How is DNA packed in mitosis ?
DNA is very densely packed
39
What are the 4 DNA replication key players ?
- Helicase - DNA polymerase - Primase - Ligase
40
What direction is the top strand read in ?
5' to 3'
41
What direction is the bottom strand read in ?
3' to 5'
42
What direction does DNA polymerase work in ?
5' to 3'
43
Where is DNA replication initiated ?
At the origin of replication
44
What bases are commonly found in the origin of replication ?
A-T as there are only 2 hydrogen bonds so easier to separate
45
How long does the G2 phase go on for ?
2-5 hours (shortest and final part of interphase)
46
What happens in G2 ?
- DNA is packed to form condensed chromosomes - Repression of gene activity (transcription)
47
What is the role of cyclin B-CDK1 ?
- They have a key role in regulating progression through mitosis - As G2 progresses this increases cyclin B levels - At the end of G2, cyclin B-CDK1 is activated
48
What happens at the G2/M checkpoint ?
- Cell is checked for DNA damage and ensures duplicated chromosomes are functional - Checks protein/growth factor levels
49
What are the 6 stages of mitosis ?
1) Prophase 2) Prometaphase 3) Metaphase 4) Anaphase 5) Telophase 6) Cytokinesis
50
What happens during prophase ?
- Chromatin condenses to visible chromosomes - Mitotic spindles start to form
51
What is a mitotic spindle ?
A structure made of microtubules which is used to align and then separate the chromosomes
52
What happens in prometaphase ?
- Nuclear membrane breaks down and disappears - Chromosomes are captured by microtubules from the centrosome - Attach at the centromere via the kinetochore - Sister chromatids sit in the middle of the cell
53
What is a kinetochore ?
A large protein structure built at the centromere which allows attachment of spindle microtubules
54
What is Lamin and where is it used ?
It is a component of the nuclear membrane and is used in prometaphase
55
What is a metaphase plate ?
The centre of the cell where chromosomes line up on
56
What happens in metaphase ?
- Chromosomes are pulled back and forth by microtubules - Chromosomes line up on the 'metaphase plate'
57
What are microtubules made of ?
Alpha and Beta tubulin
58
How are microtubules arranged and what does this mean ?
They have a + and - end. They bind together in a specific orientation to allow for differences in polarity
59
Is alpha + or - ?
Minus end of microtubules
60
Is beta + or - ?
positive end of the microtubule
61
What is the job of microtubules in metaphase ?
To position chromosomes at the metaphase plate
62
What does cyclin B-CKD1 phosphorylate in metaphase ?
Separase
63
What is the function of separase and when is it inactive ?
- It is involved in sister chromatid separation - Inactive when bound to securin - This ensures they are not split until ready
64
What is involved in the metaphase checkpoint ?
- Ensures all chromosomes are in the correct position and are properly attached to the mitotic spindle - Last checkpoint in cell cycle - If not correct cell is paused/killed
65
What happens during anaphase ?
- Sister chromatids are separated and pulled to opposite sides of the cell - Microtubules shorten - Separase destroys the link between the two sister chromatids which allows separation - CDC14b activated
66
What does CDC14b do ?
It is a phosphatase which removes a phosphate group from proteins
67
What happens during telophase ?
- Chromsomes decondense - Nuclear envelope reforms - Spindle microtubules dissolve
68
What happens during cytokinesis ?
- Cytoplasm divides and forms 2 daughter cells
69
What is a contractile ring ?
A large structural protein, composed of myosin and F-actin. This is crucial for cytokinesis and ensures the cell cleaves

Biology of the Cell (10 decks)

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