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adv biology > 1.5 protein control of cell division > Flashcards

1.5 protein control of cell division Flashcards

1
Q

what is the cytoskeleton?

A

a network of proteins extending throughout the cytoplasm, anchored to proteins in the PM

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2
Q

what is the function of the cytoskeleton?

A
  • provide mechanical support so that the cell maintains its shape
  • provide anchorage for many organelles
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3
Q

what is the cytoskeleton made of?

A

several types of protein, including microtubules

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4
Q

what are microtubules?

A

hollow cylinders made of a protein called tubulin

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5
Q

where are microtubules formed and radiated from?

A

a centrosome or MTOC (microtubule organising centre)

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6
Q

what is the role of microtubules?

A
  • govern the location and movement of the membrane-bound organelles and other cell components
  • form the spindle fibres that are active during cell division
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7
Q

how are spindle fibres formed then broken down?

A

by polymerisation and then depolymerisation of tubulin

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8
Q

what does cell division allow?

A

organisms to grow and develop, by regulating the growth and replacement of genetically identical cells

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9
Q

name the two parts into which the cell cycle can be divided

A

interphase
the mitotic phase

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10
Q

describe interphase

A

an active period of growth

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11
Q

name the three sub-phases that interphase can be divided into

A

G1, G2, S

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12
Q

describe G1

A

a growth period where proteins and organelles are synthesised

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13
Q

what happens during S phase

A

the cell continues to grow and DNA replication takes place

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14
Q

describe G2

A

another growth period

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15
Q

what happens after G2

A

the cell enters the mitotic phase

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16
Q

what happens during the mitotic phase?

A

mitosis and cytokinesis

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17
Q

what is mitosis?

A

when the nucleus and contents divide

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18
Q

what is cytokinesis?

A

the separation of the cytoplasm into daughter cells

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19
Q

what could an uncontrolled reduction in the rate of the cell cycle result in?

A

degenerative diseases

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20
Q

what could an uncontrolled increase in the rate of the cell cycle result in?

A

tumour formation

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21
Q

name the 4 stages of mitosis in order

A

prophase, metaphase, anaphase, telophase

22
Q

describe the first event of prophase

A
  • DNA condenses into discrete chromosomes with each chromosome consisting of 2 sister chromatids
23
Q

describe the second event of prophase

A
  • the nuclear membrane breaks down and spindle fibres extend from the centromere via polymerisation
24
Q

describe the final event of prophase

A

the fibres then attach to the chromosomes’ centromere at a region called the kinetochore

25
Q

what happens during metaphase?

A

the chromosomes line up at the metaphase plate at the centre of the cell

26
Q

what happens during anaphase?

A

as spindle microtubules shorten
by depolymerisation, sister chromatids are
separated, and the chromosomes are pulled
to opposite poles

27
Q

what happens during telophase?

A

the chromosomes decondense and nuclear membranes are formed around them. cytokinesis also occurs

28
Q

why must the cell cycle be controlled?

A

to ensure that events in the cycle proceed in the correct order and that each event is completed before the next starts

29
Q

how is the cell cycle controlled?

A

by checkpoints at various stages within the cell cycle

30
Q

what do checkpoints do?

A

they asses the condition of the cell and halt the progression onto the next phase until certain that all conditions have been met

31
Q

what is cyclin?

A

a protein involved in the regulation of the cell cycle by checkpoints

32
Q

what do cyclins do?

A

they combine with active and inactive cyclin-dependent kinases (CDKs) that phosphorylate other proteins which regulate the cycle

33
Q

what happens when sufficient phosphorylation is reached by CDKs?

A

progression occurs

34
Q

what does the G1 checkpoint check before the cell enters S phase?

A

that cell growth has occurred

35
Q

what happens if the G1 checkpoint finds that cell growth has not occurred?

A

the cell switches to G0 phase

36
Q

what does the G2 checkpoint check for?

A

that DNA replication has been completed and damage assessed

37
Q

what does the M checkpoint check before the cell enters anaphase?

A

that chromosomes are aligned correctly on the metaphase plate and attached to spindle fibres

38
Q

name the tumour suppressor protein at G1 checkpoint

A

retinoblastoma (Rb)

39
Q

what does the Rb protein do?

A

inhibits transcription of genes that code for proteins needed for DNA replication

40
Q

what happens at the G1 checkpoint that allows the cell to progress to S phase?

A

CDKs inhibit the Rb protein via phosphorylation, allowing transcription of the genes that code for proteins needed for DNA replication

41
Q

what is a photo-oncogene?

A

a normal gene involved in controlling cell division

42
Q

what happens when a photo-oncogene mutates?

A

it becomes a tumour-promoting oncogene, contributing to the development of cancer

43
Q

apoptosis can be triggered by … signals

A

internal or external

44
Q

what is an example of an external signal?

A

lymphocytes producing death signal molecules

45
Q

what is an example of an internal signal?

A

DNA damage

46
Q

how do external death signal molecules initiate their reaction?

A

by biding to a surface receptor protein and triggering a protein cascade inside the cytoplasm

47
Q

how does an internal death signal from DNA damage initiate its reaction?

A

activates a protein called p53

48
Q

what do both internal and external death signals result in?

A

activation of caspases (a type of protease) that cause destruction in the cell

49
Q

why is apoptosis essential during development?

A

to remove cells that are no longer required

50
Q

give an example of when apoptosis might be initiated

A

in the absence of growth factors

adv biology (13 decks)

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