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AH Biology > 1.5 Protein Control of Cell Division > Flashcards

1.5 Protein Control of Cell Division Flashcards

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1
Q

What is the cytoskeleton?

A

-Network of protein fibres that extends throughout the cytoplasm.

  • anchored to proteins in the plasma membrane
  • is constantly breaking down and re-forming to allow the cell to change shape.
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2
Q

What are the functions of the cytoskeleton?

A
  • Providing mechanical support so that cell shape can be maintained
  • Providing a method of anchoring the organelles of the cell (and some enzymes)
  • It can enable the whole cell to move
  • It can enable the organelles within a cell to move
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3
Q

What is the cytoskeleton made up of?

A

Several types of protein including microtubules

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4
Q

What are Microtubles?

A

Microtubules are around 25nm wide and are hollow, straight cylinders composed of proteins called tubulins.

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5
Q

How is the length of microtubles controlled?

A

The addition or removal of tubulin at the ends of the microtubles

(polymerisation/ depolymerisation)

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6
Q

What is the role of microtubles

A

Microtubules are responsible for the location and movement of the membrane-bound organelles and other cell components including chromosomes.

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7
Q

Where do microtubles originate from?

A

The microtubule-organising centre (MTOC)

Or the centrosome which is located near the nucleus and contains centrioles, which are the site of microtubule synthesis.

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8
Q

Describe the role of microtubles in Cell division

A

used in remodelling of the cell’s cytoskeleton.

also form the spindle fibres which are active during cell division.

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9
Q

What is the purpose of cell division?

A

Cell division is a vial process that allows an organism to grow and develop, to replace dead cells and repair tissue.

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10
Q

What are the two stages of cell division?

A

interphase and the mitotic phase

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11
Q

During the interphase a cell is undergoing…….

A

a period of growth which involves

  • protein synthesis
  • creation of the organelles
  • the replication of chromosomes
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12
Q

What are the 3 stages of interphase?

A

G1
S phase
G2

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13
Q

Describe G1

A

G1 is the first growth/gap phase, during this time proteins and organelles are synthesised

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14
Q

What happens in the S phase

A

S phase involves the replication of DNA

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15
Q

What happens in G2

A

G2 is the second growth/gap phase which also involves the synthesis of proteins and organelles.

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16
Q

What are the stages of mitosis?

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
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17
Q

Describe the events occuring in prophase

A
  • DNA condenses into chromosomes each consisting of two sister chromatids.
  • The nuclear membrane breaks down
  • spindle microtubules extend from the MTOC (by polymerisation) and attach to chromosomes via their kinetochores in the centromere region
18
Q

Describe the events occuring in Metaphase

A

chromosomes are aligned at the metaphase plate (equator of the cell/spindle)

19
Q

Describe the events occurring in Anaphase

A

As spindle microtubules shorted (by depolymerisation) sister chromatids are separated and the chromosomes are pulled to opposite poles

20
Q

Describe the events occurring in Telophase

A

the chromosomes decondense and the nuclear membranes are formed around them.

21
Q

What is the final part of the cell cycle?

A

Cytokinesis

22
Q

What happens during cytokinesis

A

Cytoplasm splits to form two daughter cells.

23
Q

Why must cell be produced at the correct rate and in the correct locations

A

to allow regulated growth and repair

24
Q

An uncontrolled reduction in the rate of the cell cycle will result in…..

Because……..

A

degenerative disease such as Alzheimer’s or Parkinson’s as insufficient replacement cells are being formed for normal tissue function

25
Q

An uncontrolled increase in the rate of the cell cycle may result in…..

A

the formation of tumours. Uncontrolled growth may be benign or may result in a malignant cancer

26
Q

What is a proto-oncogene?

A

A proto-oncogene is a normal gene that can mutate to form a tumour-promoting oncogene

27
Q

What is progression of the cell cycle controlled by?

A

Checkpoints

28
Q

What types of signalling is used to control the cell cycle

A

internal and external

29
Q

Which proteins accumulate during cell growth and what is their role?

A

Cyclin proteins that accumulate during cell growth are involved in regulating the cell cycle

30
Q

What do cyclins combine with and activate?

A

cyclin-dependent kinases (CDKs)

31
Q

What do Active cyclin-CDK complexes do?

A

phosphorylate proteins that regulate progression through the cycle

32
Q

The next stage of the cell cycle will occur if

A

sufficient phosphorylation is reached

33
Q

Describe What occurs at the G1 Checkpoint

A

This occurs towards the end of G1. At this checkpoint:

  • retinoblastoma protein (Rb) acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication.
  • Phosphorylation by G1 cyclin-CDK inhibits the Rb. This allows transcription of the genes that code for proteins needed for DNA replication. The cell can then progress from G1 to S phase.
34
Q

Describe the G2 Checkpoint

A

Occurs at the end of G2, the success of DNA replication and any damage to DNA is assessed.

  • DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death.
35
Q

Describe the M Checkpoint

A
  • Occurs during metaphase
  • controls progression from metaphase to anaphase.
  • At this checkpoint, progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules.
36
Q

Apoptosis is triggered by…..

A

cell death signals that can be external or internal

37
Q

How are External death signals transmitted

A
  • External death signal molecules bind to a surface receptor protein
  • trigger a protein cascade within the cytoplasm
38
Q

Describe Internal death signals

A

Internal death signal resulting from DNA damage causes activation of p53 tumour suppressor protein

39
Q

Death signals result in……

A

The activation of caspases (types of protease enzyme)
that cause the destruction of the cell

40
Q

Why is Apoptosis important?

A

Removes cells no longer required as development progresses or during metamorphosis

41
Q

Cells may initiate apoptosis in the absence of….

A

Growth Factors

42
Q
A

AH Biology (10 decks)

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