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Cellular Biology and Biochemistry > Cell growth and proliferation > Flashcards

Cell growth and proliferation Flashcards

1
Q

How do normal cells respond to the body needing them?

A

They divide when needed

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2
Q

Give examples of when cell proliferation is needed

A 
Tissue maintenance
Embryogenesis
Repairing wounds
Adapting to the environment
Fighting infection
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3
Q

What happens when cell proliferation controls are lost?

A

Cancer

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4
Q

Do all cells in the body have the ability to divide?

A

No

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5
Q

What are stem cells?

A

Present in small numbers in tissues
Responsible for re-seeding proliferating precursor cells which differentiate to replace dying cells to maintain the tissue

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6
Q

Give an example of stem cells

A

Intestinal stem cells
Found in the intestinal crypt
Cells divide in the proliferation zone and move out of the crypt
Cells die by apoptosis and are replaced

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7
Q

What stimulates cell proliferation?

A

Mitogenic signals

Growth factors

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8
Q

What is the equation for cell proliferation?

A

Cell growth + cell division

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9
Q

Define cell growth

A

Increase in cell size

Increase in cytoplasmic organelles

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10
Q

Define cell division

A

Chromosome duplication
Mitosis
Cytokinesis

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11
Q

What happens in interphase?

A

G1, S and G2
Cell grows
Nuclear DNA duplicated

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12
Q

What happens in mitosis and cytokinesis?

A

Nucleus and cytoplasm divide to form two daughter cells

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13
Q

What regulates the cell cycle?

A

Cyclin-dependent kinases

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14
Q

Describe a cyclin dependent kinase

A

Cyclin binds to, and activates, cyclin-dependent kinase

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15
Q

What do cyclin dependent kinases do?

A

Phosphorylate proteins that are important during specific cell cycle phases

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16
Q

What regulates the different phases of the cell cycle?

A 
Different cyclin-CDK dimers
e.g. 
G1/S-Cdk
S-Cdk
M-Cdk
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17
Q

Which subunits are generally present throughout?

A

Cdk catalytic subunits 1,2,4,6

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18
Q

Which subunits have fluctuating levels?

A

Cyclin regulatory subunits

A,B,D,E

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19
Q

What is essential in the cell cycle?

A 
Increase the cell size and cytoplasmic organelles
Overcome restriction point
Replicate the chromosomes once
Fully duplicate the chromosomes
Separate the duplicated chromosomes
Separate the two daughter cells
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20
Q

What is the restriction point in G1?

A

The R point is a checkpoint through which cells can only progress if appropriately stimulated by mitogens

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21
Q

What is needed to get through the restriction point?

A

Mitogenic growth factor signalling

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22
Q

What do mitogenic growth factors signal for?

A

Transcription factors of immediate early genes

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23
Q

What do the immediate early genes code for?

A

Transcription of cyclinD which binds to Cdk 4 or 6 to form G1-Cdk

24
Q

What does G1-Cdk do?

A

Binds to the retinoblastoma protein to enable progression through the R point

25
Q

What is require to inactivate pRb?

A

G1-Cdk and G1/S-Cdk

26
Q

What does pRb repress?

A

Transcription of cell cycle genes
Binds to E2F
Prevents transcription of genes for Cyclin E and A

27
Q

How do the cyclin dependent kinases inactive pRb?

A

By phosphorylation

28
Q

What triggers the replication of chromosomes in the S phase?

A

S-Cdk

29
Q

What is the G2 checkpoint?

A

Cells cannot enter mitosis until they have completely replicated their chromosomes in S phase

30
Q

What is inactive until the S phase has been completed?

A

M-Cdk

31
Q

What is required for entry into mitosis?

A

M-Cdk activation

32
Q

How is M-Cdk inactivated and activated?

A

Inactived by Wee1
Phosphorylation
This stops once all chromosomes have been replicated

33
Q

What are the four stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

34
Q

What happens in prophase?

A

Chromosome condensation
Nuclear envelope breakdown
Spindle formation and connection to kinetochores

35
Q

What happens in metaphase?

A

Chromosomes align between two spindle poles

36
Q

What happens in anaphase?

A

Chromosome separation

37
Q

What happens in telophase?

A

Nuclear envelope reformation

Chromosome decondensation

38
Q

What is the kinetochore?

A

Forms from the central region of the chromatids known as the centromere
Where mitotic spindles attach

39
Q

Where do mitotic spindles form from?

A

Two spindle poles outside of the nucleus

40
Q

When will chromosome separation occur?

A

In anaphase

Once all kinetochores are attached to spindle poles by mitotic spindles

41
Q

What prevents the onset of anaphase?

A

Chromosomes with an unattached kinetochore send out a stop signal

42
Q

What is the anaphase promoting complex?

A

When all kinetochores are attached

43
Q

What results from the anaphase promoting complex?

A

Destruction of proteins holding sister chromatids together

44
Q

How does cytokinesis occur?

A

A cleavage furrow forms by the action of a contractile ring

Contracts further to separate the daughter cells

45
Q

What is aneuploidy?

A

Altered chromosome number

46
Q

What does DNA damage activate?

A

P53

A tumour suppressor protein

47
Q

What does p53 induce?

A

p21

A Cdk inhibitor

48
Q

What does p21 do?

A

Inhibits G1/S-Cdk, S-Cdk, M-Cdk
Cell cycle cannot pass through checkpoints
Damaged DNA is not replicated

49
Q

When is apoptosis necessary?

A

In development
(Fingers and toes)
When cells are no longer required
When cells are damaged

50
Q

What are the stages of apoptosis?

A

Initiatior caspases
Executioner caspases
Cell breaks up into membrane bound fragments called apoptotic bodies
Dead cells are removed by phagocytosis

51
Q

How is apoptosis different from necrosis?

A

Necrosis provokes an inflammatory response

52
Q

What are caspases?

A

Enzymes required for apoptosis

Activated by death stimuli

53
Q

How are caspases activated?

A

Inactive form is procaspases

Cleaved of pro domains and combined

54
Q

What do initiator caspases activate?

A

Executioner caspases

55
Q

What do executioner caspases do?

A

Degrade nuclear and cytosolic proteins

56
Q

What avoids apoptosis?

A

Survival signals from neighbouring cells

Cellular Biology and Biochemistry (22 decks)

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