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AH Biology > Protein Control of Cell Division > Flashcards

Protein Control of Cell Division Flashcards

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

Function of the cytoskeleton

A

Gives mechanical support and shape to cells

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3
Q

The cytoskeleton consists of…

A

Different proteins including microtubules

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4
Q

What are microtubules?

A

Hollow cylinders composed of the protein tubulin
Radiate from the microtubule organising centre (MTOC) or centrosome

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5
Q

Function of microtubules

A

Control the movement of membrane-bound organelles and chromosomes

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6
Q

Cell division requires the…

A

Remodelling of the cytoskeleton

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7
Q

What is the remodelling of the cytoskeleton?

A

Formation and breakdown of microtubules, involves polymerisation (growth) and depolymerisation (shrinkage) of tubulin

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8
Q

Microtubules form…

A

Spindle fibres that are active during cell division

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9
Q

What does the cell cycle regulate?

A

The growth and replacement of genetically identical cells throughout the life of the organism

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10
Q

2 stages of cell cycle…

A

Interphase
Mitotic (M) Phase

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11
Q

Interphase involves…

A

G1- a growth phase
S phase- DNA is replicated
G2- a further growth phase (of organelles and proteins)
(preparation for mitosis)

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12
Q

Mitotic phase involves…

A

Mitosis- chromosomal material is separated by the spindle microtubules
Cytokinesis- cytoplasm is separated into 2 daughter cells

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13
Q

4 stages of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

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14
Q

What happens during prophase?

A

DNA condenses into chromosomes (consist of 2 sister chromatids)
Nuclear membrane breaks down, spindle microtubules extend from MTOC by polymerisation and attach to chromosomes via their kinetochores in the centromere region

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15
Q

What happens during metaphase?

A

Chromosomes are aligned at the metaphase plate (equator of the spindle)

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16
Q

What happens during anaphase?

A

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

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17
Q

What happens during telophase?

A

Chromosomes decondense and nuclear membranes are formed around them (each set of chromosomes)

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18
Q

Progression through the cell cycle is controlled by…

A

Checkpoints

19
Q

What are checkpoints?

A

Mechanisms within the cell that assess the condition of the cell during the cell cycle and halt progression to the next phase until certain requirements are met

20
Q

What are the 3 checkpoints?

A

G1 checkpoint
G2 checkpoint
Metaphase checkpoint

21
Q

G1 checkpoint…

A

Occurs towards end of G1
Sufficient cell growth must have occurred before cell can enter S phase

22
Q

G2 checkpoint…

A

Occurs towards end of G2
Success of DNA replication and any damage to DNA is assessed

23
Q

Metaphase checkpoint…

A

Occurs during metaphase and controls entry to anaphase
Progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules

24
Q

What does retinoblastoma protein (Rb) do?

A

Acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication

25
Q

What do cyclin proteins do?

A

Accumulate during cell growth and are involved in regulating the cell cycle
Combine with and activate cyclin-dependent kinases (CDK’s)

26
Q

Active cyclin-CDK complexes…

A

Phosphorylate proteins that regulate progression through the cycle, if sufficient phosphorylation is reached the progression occurs

27
Q

Phosphorylation by G1 cyclin-CDK…

A

Inhibits retinoblastoma protein allowing transcription of genes that code for proteins needed for DNA replication (therefore cells can progress from G1 to S phase)

28
Q

At G2 checkpoint, DNA damage triggers the activation of several proteins such as…

A

p53 which can…
Stimulate DNA repair
Arrest cell cycle
Cause cell death (initiate apoptosis) if DNA damage is too severe

29
Q

What does an uncontrolled reduction of cell cycle rate lead to?

A

Degenerative disease e.g. Alzheimers

30
Q

What does an uncontrolled increase in cell cycle rate lead to?

A

Tumour formation (cancer)

31
Q

What is a photo-oncogene?

A

Normal gene usually involved in the control of cell growth or division
Can mutate to form tumour promoting oncogene

32
Q

What triggers apoptosis?

A

Cell death signals

33
Q

Why must destruction of cells in multicellular organisms be carefully controlled?

A

Excessive apoptosis leads to degenerative conditions
Inhibition of apoptosis leads to tumour formation

34
Q

Where do external cell death signals originate?

A

Out with cell

35
Q

Where do internal cell death signals originate?

A

Within cell

36
Q

Example of external cell death signal

A

Production of death signal molecules from lymphocytes

37
Q

External death signal molecules bind to…

A

A surface receptor protein, triggering a protein cascade within cytoplasms

38
Q

Example of internal cell death signal

A

DNA damage

39
Q

Internal death signal resulting from DNA damage results in…

A

Activation of p53 tumour-suppressor protein

40
Q

Both types of cell death signal result in…

A

Activation of caspases

41
Q

What are caspases?

A

Types of protease enzyme that cause destruction of cells

42
Q

When else might cells initiate apoptosis ?

A

In the absence of growth factors

43
Q

Apoptosis is essential during…

A

Development of am organism to remove cells no longer required as development progresses
Metamorphosis (when an animal changes from after hatching/birth)

AH Biology (13 decks)

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