Apoptosis and quiescence lectures Flashcards

1
Q

Apoptosis define

A

Eliminates cells with DNA damage that fail to be repaired at G1/S or G2/M
Crucial to cell number and morphogenesis
eg. eliminates self-lymphocytes

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2
Q

What morphology of apoptosis can be observed under a microscope?

A

Cell shrinkage, nuclear condensation/fragmentation, chromosome condensation, releasing apoptotic bodies containing organelles, blebbing(bulges)

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3
Q

How do macrophages recognise apoptotic cells?

A

Phoshatidylserine exposure (which is usually in cytoplasmic portion of PM)

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4
Q

What did C Elegans studies reveal?

A

Pro- (BAX, BAK) and anti- (BCL2 and BCL-XL)apoptotic factors, executioner factors (proteolytic enzymes) which cause cascade of digestion destroying cellular contents

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5
Q

What ultimately triggers a proteolytic cascade?

A

Mitochondria

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6
Q

What is apoptosis triggered in response to?

A

DNA damage, loss of growth factor signalling, loss of contact with basement membrane, ER stress(accumulation of unfolded proteins in ER lumen)

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7
Q

Draw diagram of BAX and BAK causing apoptosis

A

See notes for diagram

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8
Q

What receptor family are important in triggering apoptosis?

A

Death domain

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9
Q

What do death domain receptors bind?

A

TNF alpha (produced by macrophages) or FasL (on surface of cytotoxic lymphocytes produced in immune response)

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10
Q

What is quiescence?

A

Cells exit cell cycle, used by memory lymphocytes to preserve pathogen memory

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11
Q

In quiescence:

A

Cells lower metabolic energy, exit cell cycle, reduce ribosome biogenesis and protein production
Wait until external signal for active cycling
Minimal damage from ROS and low chance of mutation

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12
Q

What is a cell niche?

A

Allows necessary cell-cell and cell-matrix interactions, could promote quiescence eg. CDK inhibitors preventing G1 entry

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13
Q

Where are epidermal stem cells?

A

Deepest most basal layer of skin (hypodermis), protected by melanin

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14
Q

Epidermal stem cells…

A

Regularly regenerate the entire skin, are quiescent but can be activated at any point

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15
Q

What is the point of a 3’ UTR?

A

Allows low translational activity in quiescence, miRNAs bind and prevent translation of mRNA with 3’ UTR (NB mRNA is normally translated 5’ to 3’)

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16
Q

Draw stem cell diagram

A

See notes for diagram

17
Q

How are quiescent cells poised to reenter the cell cycle?

A

They have loose DNA and histones allowing TF access, histones have post-translational modifications typical of active transcriptional state
RNA pol kept paused due to binding by negative regulators preventing transcription

18
Q

What happens upon cell activation?

A

RNA pol is released, there is no need to reset transcriptional programme, cell is good to go

19
Q

What is fancy name for increase in cell size?

A

Hyperplasia

20
Q

Increase in cell no=?

A

Hypertrophy

21
Q

What is the growth law in bacteria?

A

Larger cells proliferate faster and thus maintain cell size uniform under steady state

22
Q

When is uniform cell size lost in multicellular organisms?

A

In injury and cancer

23
Q

What happens to WAC

A

They expand in number in late embryonic life to a stable number, so adipose tissue grows by accumulation of lipid particles due to diet and no increase in number (hypertrophy)

24
Q

What factor regulates adipocyte development and height?

A

Insulin growth factor 1

Participates in cartilage hypertrophy during bone formation of growing limb bones in adolescents

25
Q

What does research show about amount eaten as child and liklihood of being obese?

A

The more you eat as a baby the more likely you are to be obese because no. adipose cells set v early, cells store more fat if you eat more as a child

26
Q

In pregant women beta cells…

A

Increase in size not number to meet higher blood glucose demands, to make more insulin, as increasing in size is less risky for mistake/cancer than increasing in number