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AH biology - unit 1 (Proteomics) > Unit 1.5 - Protein control of cell division > Flashcards

Unit 1.5 - Protein control of cell division Flashcards

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1
Q

What is the cytoskeleton?

A

Network of protein fibres that extend throughout the cytoplasm in all eukaryotic cells

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2
Q

Give some functions of the cytoskeleton

A

Provide mechanical support so cell maintains shape
Provides anchorage for many organelles
Allow the whole cell to move
Enable organelles within the cell to move

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3
Q

What are microtubules made of?

A

Polymers of a dimer consisting of alpha tubulin and beta tubulin

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4
Q

How is the length of microtubules controlled?

A

Addition or removal of tubulin at the ends of the microtubules

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5
Q

What is the function of microtubules?

A
  • determine cell shape and involved in movement in cell
  • They form the spindle fibres to separate chromosomes during
    cell division.
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6
Q

Where do microtubules radiate from?

A

Microtubules Organising Centre (MTOC)

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7
Q

Where is the MTOC located and what does it contain?

A

Near the nucleus

Centrosome

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8
Q

What are the three roles of microtubules in cell division?

A
  1. Each centrosome ensures that the cell division apparatus is located at the correct position
  2. Spindle microtubules attach to kinetechore proteins at the centrosomes of each chromatid
  3. Microtubules attach to microtubules from the opposite centrosome
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9
Q

How are the chromatids seperated during cell division?

A

Disassembly of the microtubules at the kinetchores

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10
Q

What are the two phases of the cell cycle?

A

Interphase and Mitosis

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11
Q

What are the three phases of interphase?

A

G1, S, G2

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12
Q

What happens in the G1 stage of interphase?

A

First growth stage

Cell makes copies of new proteins and organelles

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13
Q

In what stage of interphase does DNA replication occur?

A

S

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14
Q

What occurs in the G2 phase of cell division

A

Second growth phase

Cell makes more proteins and copies organelles in prep for mitosis

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15
Q

What are the five stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase
Cytokenesis

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16
Q

What happens during prophase?

A

Chromosomes condense
Each chromosomes is composed of two chromatids
Microtubules start to assemble to the spindle fibres
Some spindle fibres attach to the kinetechore

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17
Q

In what stage are the sister chromatids pulled apart?

A

Anaphase

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18
Q

What happens in Telophase?

A

Seperated chromosomes are pulled to opposite poles
Chromosomes form daughter nuclei
Chromosomes start to uncoil and nucleur membrane forms

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19
Q

Where do chromosomes line up in metaphase?

A

Metaphase plate at the equator of the cell

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20
Q

What happens during metaphase?

A

Chromosomes line up on the metaphase plate at equator of cell
Movement acheived by assembly/diassembly of tubulin dimers

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21
Q

How do spindle fibres contract and expand?

A

Addition and removal of dimers onto the spindle fibres

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22
Q

What is Cytokenesis?

A

Division of the cytoplasm to form two daughter cells

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23
Q

What is the mitotic index?

A

Percentage of cells undergoing mitosis in the sample

24
Q

What may be indicated from an abnormally high mitotic index in a sample?

A

Developing tumour

25
Q

What can an uncontrolled reduction in the rate of the cell cycle cause?

A

Degenerative diseases

e.g. Alzheimer’s disease

26
Q

What is one of the causes of cancer?

A

Uncontrolled increase in the rate of the cell cycle

27
Q

Where are the checkpoints in the cell cycle?

A

G1, G2, M

28
Q

What are checkpoints?

A

Critical control points where stop and go-ahead signals regulate the cycle

29
Q

What is checked at the G1 checkpoint?

A

Cell size is monitored

30
Q

Which checkpoint regulates entry to G0/S phase?

A

G1 checkpoint

31
Q

What is assessed at the G2 checkpoint?

A

Success of DNA replication

32
Q

Describe the M checkpoint

A

occurs during metaphase
monitors chromosome alignment
makes sure each daughter cell receives one chromatid from each chromosome
controls entry to anaphase

33
Q

what accumulates as cell size increases in the g1 phase?

A

cyclins

34
Q

What do cyclins combine with?

A

Cyclin Dependant Kinases

35
Q

What does the binding of cyclin and CDKS form?

A

Mitosis Promoting Factor

36
Q

What do active CDKs do?

A

Phosphorylate target proteins that stimulate the cell cycle

37
Q

What is Rb?

A

Restinoblastoma protein is a transcription protein important at the G1 checkpoint

38
Q

What is Rb involved with?

A

Production of proteins required for DNA replication in the S phase

39
Q

What phosphorylates Rb?

A

CDKs

40
Q

What happens when the activity of CDKs reaches a sufficient threshold?

A

Each Rb has been phosphorylated 14 times and so can no longer bind to the transcription factors, allowing the cell to progress past the G1 checkpoint into S

41
Q

What is p53?

A

A transcription factor

42
Q

What are the three functions of p53?

A

Stimulate DNA Repair
Arrest the cell cycle
Trigger apoptosis

43
Q

What happens if DNA damage has occured?

A

p53 causes the expression of genes to stimulate DNA repair, arrests the cell cycle

44
Q

What happens if DNA repair is not successful?

A

p53 instructs the cell to kill itself

45
Q

What is apoptosis?

A

Programmed cell death

46
Q

What is apoptosis triggered by?

A

Cell death signals

47
Q

Where can cell death signals come from?

A

Extracellular signals or intracellular signals (inside or outside of the cell)

48
Q

Give an example of a cell death signal that originates from outside the cell

A

Lymphocyte / Natural Killer Cell

49
Q

What happens in the case of an external cell death signal?

A

Ligand binds to a receptor protein
Causes a conformational change on the cytoplasmic side
Acts as a signal transduction and activates a protein cascase that produces caspases

50
Q

When may a cell death signal originate from inside the cell?

A

When DNA damage is detected

Absence of cell growth factors

51
Q

How is a caspase cascade initiated?

A

Caspases must be activated
Inactive proteinases and DNAases are activated
Initiator caspases activate executioner caspases
Degrade cellular components

52
Q

What is the cause of the fact that the cell breaks into many small vesicles?

A

Lack of intact cytoskeleton

53
Q

During interphase if cell size is not large enough, what occurs?

A

G0 (non-diving phase)

54
Q

If cell is large enough during interphase and proceeds to S phase, what occurs?

A
  • cyclin proteins accumulate during cell growth + kinase
  • active CDK phosphorylate target proteins (e.g. Rb)
  • sufficient threshold -> S phase
  • insufficient threshold -> G0 phase
55
Q

What occurs when active CDKs have sufficient threshold?

A
  • Rb does not bind to E2F
    -E2F free to bind with DNA + promote transcription
  • S phase
56
Q

What occurs when active CDKs have insufficient threshold?

A
  • Rb binds to E2F
  • E2F cannot bind to DNA
    -transcription inhibited
  • G0 phase

AH biology - unit 1 (Proteomics) (11 decks)

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