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Biology > U1: KA5 - Control Of Cell Division > Flashcards

U1: KA5 - Control Of Cell Division Flashcards

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1
Q

What is the cytoskeleton?

A

Network of proteins throughout the cytoplasm anchored to proteins in the plasma membrane and is constantly breaking and re-forming (dynamic)

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2
Q

What are microtubules?

A

Hollow straight cylinders composed of globular proteins called proteins.

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3
Q

Growth of microtubule involves……. And shrinking of tubulin involves…….

A

Polymerisation
Depolymerisation

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4
Q

Microtubules radiate from the?

A

MTOC/centrosome

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5
Q

What are the functions of the cytoskeleton?

A

Mechanical support and shape to cells
Control movement of membrane bound organelles and chromosomes
Important role in cell division, requires remodelling of the cells cytoskeleton. Microtubules form spindle fibres.

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6
Q

What type of cell is the cytoskeleton present in?

A

Eukaryotes

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7
Q

Is the cytoskeleton dynamic or fixed?

A

Dynamic

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8
Q

Location of cytoskeleton?

A

Centrosome

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9
Q

What are the 2 parts of the cell cycle?

A

Interphase
Mitotic phase

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10
Q

Describe the interphase.

A

Lasts much longer than mitotic phase. Active period of growth.

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11
Q

What is the first phase of the interphase?

A

G1 - growth period where protein’s and organelles are synthesised.

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12
Q

Describe the second phase of the interphase.

A

S phase cell continues to grow and DNA is replicated in preparation for mitosis.

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13
Q

Describe the third phase of the interphase.

A

G2 - another growth period during which proteins and organelles are synthesised.

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14
Q

Describe the mitotic phase.

A

At end of G2 cells enter the mitotic phase which is divided up into two stages.

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15
Q

What is stage one of the mitotic phase?

A

Mitosis - chromosomal material is separated

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16
Q

What is the second stage of mitotic phase?

A

Cytokinesis - separation of cytoplasm into daughter cells.

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17
Q

What are the stages of mitosis?

A

P - prophase
M - metaphase
A - anaphase
T - telophase

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18
Q

Describe the first stage of mitosis l.

A

Prophase - DNA condenses into chromosomes each consisting of two sister chromatids. Nuclear membrane breaks down spindle microtubules extend from the MTOC by polymerisation and attach to chromosomes via their kinetochores in the centrosome region.

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19
Q

Describe the metaphase.

A

Chromosomes are aligned at the metaphase plate. (Equator of the spindle)

20
Q

Describe the anaphase.

A

As spindle microtubules shorten by depolymerisation sister chromatids are separated and chromosomes are pulled to opposite poles.

21
Q

Describe the telophase.

A

Chromosomes decondese and nuclear membranes are formed around them.

22
Q

Functions of the microtubules in the cell cycle.

A

Aligning chromosomes on metaphase plate
Separating sister chromatids
Formation of daughter nuclei

23
Q

Progression through the cell cycle is regulated by?

A

Checkpoints.

24
Q

What is the G1 checkpoint?

A

Occurs towards the end of G1; sufficient cell growth must have occurred before cell can enter S phase.

25
Q

When does G2 checkpoint occur?

A

End of G2; success of DNA replication is assessed

26
Q

When does the M checkpoint occur?

A

Occurs during metaphase and controls entry to anaphase. Checks that chromosomes are aligned correctly on the metaphase plate; therefore ensures that each daughter cell receives the correct number of chromosomes.

27
Q

Describe the G1 checkpoint.

A

Most important
If cell receives the go ahead signal at this checkpoint it will usually complete the cycle.
If not it will exit the cycle and switch to a non-dividing state called the G0 phase.

28
Q

As the cell size increases during G1 what happens.

A

Cyclin proteins accumulate, they are involved in cell growth and in regulating the cell cycle.

29
Q

Cyclins combine with….

A

Cyclin-dependent kinases. (CDKs)
Activating it

30
Q

What do active cyclin-CDK complexes do?

A

Phosphorylate proteins that regulate progression through the cell cycle.
If theres a sufficient threshold of phosphorylation: cell cycle moves on to the next stage.
If there’s an insufficient threshold reached: the cell is held at the checkpoint.

31
Q

What is retionblastoma?

A

A protein that acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication.
G1 CDKs phosphorylate the rb protein. Phosphorylation inhibits Rb.
This allows transcription of the genes that code for proteins needed for DNA replication. Cells therefore progress from G1 to S phase.

32
Q

What happens at the G2 checkpoint?

A

Success of DNA replication and any damage to DNA is assessed.

33
Q

DNA damage triggers what?

A

Activation of several proteins including p53.

34
Q

What can p53 do?

A
  • Stimulate DNA repair
  • Arrest the cell cycle (allows time to recognise and fix DNA damage so cell can restart the cell cycle)
  • Initiate apoptosis (programmed death)
35
Q

Describe the metaphase checkpoint.

A

Progression is halted until chromosomes are aligned correctly on the metaphase plate and attached to spindle microtubules.

36
Q

What can an uncontrolled reduction of cell cycle rate result in?

A

Degenerative disease.

37
Q

What can an uncontrolled increase in rate of cell cycle result in?

A

Tumour formation

38
Q

What is a proto-oncogene

A

Normal gene usually involved in the control of cell growth or division which can mutate to form a tumour promoting oncogene.

39
Q

What is apoptosis?

A

Programmed cell death.

40
Q

What triggers apoptosis?

A

Cell death signals either external or internal.

41
Q

What do you call cell death signals which originate out with the cell and what’s an example of them?

A

Extrinsic e.g - lymphocytes

42
Q

How do external death signal molecules work?

A

Bind to surface receptor protein to trigger a protein cascade within the cytoplasm.

43
Q

Explain intrinsic cell death signals.

A

DNA damage is an example of internal cell death signaling.
It trigger the activation of p53 tumour suppressor protein.

44
Q

Both types of death signaling molecules trigger what?

A

Capases. Types of protease enzyme.
Proteinases bring about degradation of cellular proteins. Causing the destruction of the cell.

45
Q

Cells may also initiate apoptosis in the absence of what?

A

Growth factors

46
Q

What’s the importance of apoptosis?

A

Essential during the development of an organism to remove cells no longer required as development progresses.

Metamorphosis

Biology (5 decks)

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