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

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

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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
Q

What cyclin is used in G2 and M?

A

Cyclin B

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26
Q

What does CDK stand for ?

A

Cyclin dependant kinases

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27
Q

What CKDs bind to cyclin D ?

A
  • CDK4
  • CDK6
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28
Q

What CDK binds to cyclin E and cyclin A ?

A

CDK2

29
Q

What CDK binds to cyclin B ?

A

CDK1

30
Q

When are CDKs active ?

A

When bound to a cyclin

31
Q

What happens in step 1 of the cell cycle- early G1 (3) ?

A
  • 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
Q

What happens in step 2 of the cell cycle- late G1 ?

A
  • 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
Q

What happens at the G1 checkpoint ?

A
  • 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
Q

What protein is a crucial component of the G1 checkpoint ?

A

p53

35
Q

How long does the S phase take ?

A

10-12 hours (half cell cycle)

36
Q

What is the aim of the S phase ?

A
  • To accurately copy DNA
  • Avoid mutations
  • DNA must be distributed so that daughter cells have an identical genome
37
Q

How long in m in chromosomal DNA ?

A

2m long

38
Q

How is DNA packed in mitosis ?

A

DNA is very densely packed

39
Q

What are the 4 DNA replication key players ?

A
  • Helicase
  • DNA polymerase
  • Primase
  • Ligase
40
Q

What direction is the top strand read in ?

A

5’ to 3’

41
Q

What direction is the bottom strand read in ?

A

3’ to 5’

42
Q

What direction does DNA polymerase work in ?

A

5’ to 3’

43
Q

Where is DNA replication initiated ?

A

At the origin of replication

44
Q

What bases are commonly found in the origin of replication ?

A

A-T as there are only 2 hydrogen bonds so easier to separate

45
Q

How long does the G2 phase go on for ?

A

2-5 hours (shortest and final part of interphase)

46
Q

What happens in G2 ?

A
  • DNA is packed to form condensed chromosomes
  • Repression of gene activity (transcription)
47
Q

What is the role of cyclin B-CDK1 ?

A
  • 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
Q

What happens at the G2/M checkpoint ?

A
  • Cell is checked for DNA damage and ensures duplicated chromosomes are functional
  • Checks protein/growth factor levels
49
Q

What are the 6 stages of mitosis ?

A

1) Prophase
2) Prometaphase
3) Metaphase
4) Anaphase
5) Telophase
6) Cytokinesis

50
Q

What happens during prophase ?

A
  • Chromatin condenses to visible chromosomes
  • Mitotic spindles start to form
51
Q

What is a mitotic spindle ?

A

A structure made of microtubules which is used to align and then separate the chromosomes

52
Q

What happens in prometaphase ?

A
  • 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
Q

What is a kinetochore ?

A

A large protein structure built at the centromere which allows attachment of spindle microtubules

54
Q

What is Lamin and where is it used ?

A

It is a component of the nuclear membrane and is used in prometaphase

55
Q

What is a metaphase plate ?

A

The centre of the cell where chromosomes line up on

56
Q

What happens in metaphase ?

A
  • Chromosomes are pulled back and forth by microtubules
  • Chromosomes line up on the ‘metaphase plate’
57
Q

What are microtubules made of ?

A

Alpha and Beta tubulin

58
Q

How are microtubules arranged and what does this mean ?

A

They have a + and - end. They bind together in a specific orientation to allow for differences in polarity

59
Q

Is alpha + or - ?

A

Minus end of microtubules

60
Q

Is beta + or - ?

A

positive end of the microtubule

61
Q

What is the job of microtubules in metaphase ?

A

To position chromosomes at the metaphase plate

62
Q

What does cyclin B-CKD1 phosphorylate in metaphase ?

A

Separase

63
Q

What is the function of separase and when is it inactive ?

A
  • It is involved in sister chromatid separation
  • Inactive when bound to securin
  • This ensures they are not split until ready
64
Q

What is involved in the metaphase checkpoint ?

A
  • 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
Q

What happens during anaphase ?

A
  • 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
Q

What does CDC14b do ?

A

It is a phosphatase which removes a phosphate group from proteins

67
Q

What happens during telophase ?

A
  • Chromsomes decondense
  • Nuclear envelope reforms
  • Spindle microtubules dissolve
68
Q

What happens during cytokinesis ?

A
  • Cytoplasm divides and forms 2 daughter cells
69
Q

What is a contractile ring ?

A

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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