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CHI > cell death and apoptosis > Flashcards

cell death and apoptosis Flashcards

1
Q

what are the two types of cell death

A

apoptosis and necrosis

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2
Q

what is necrosis

A

accidental cell death

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3
Q

what is apoptosis

A

programmed cell death

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4
Q

what are the structural changes that occur during apoptosis

A

-small blebs form ; organelles are located in the blebs
- the nucleus begins to break apart and DNA breaks into small pieces
-the cell then breaks into several apoptotic bodies

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5
Q

what are the structural changes that occur during necrosis

A

blebs form and the structure if the nucleus changes
- blebs fuse to become larger; no organelles are located in the blebs
-cell membrane ruptures and content is released; the organelles are not functional

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6
Q

why does cell death occur

A

in response to infection and damage
- during embryonic development
- to maintain homeostasis
- to eliminate damaged cells

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7
Q

how is apoptosis regulated

A

by cell-cell interactions

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8
Q

why is apoptosis needed

A
  • to sculpt tissues and organs during embryonic development
  • to maintain cell number
  • to eliminate dead, infected or potentially cancerous cells
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9
Q

what are the 3 cell stages of apoptosis

A

-pre apoptotic cell
- early apoptotic cells
- late apoptotic cell

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10
Q

what occurs during pre-apoptotic cell

A
  • mild convolution of membrane
  • chromatin compaction
  • cytoplasm condensation
  • (cell shrinks, DNA fragmentation, nuclear condensation)
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11
Q

what occurs during early apoptotic cell stage

A
  • cell shrinkage
  • membrane blebbing
  • break up of nuclear envelope
  • condensation of nucleus and cytoskeleton
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12
Q

what occurs during late-apoptotic cell stage

A
  • irregular extensions break away and are phagocytosed
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13
Q

what is a caspase

A

an effector protease involved in apoptosis

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14
Q

what are caspases produced as

A

inactive monomeric pro-caspases

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15
Q

what must happen to pro-caspases in order to form caspases

A

they must be cleaved

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16
Q

what type of proteins are caspases and what do they contain

A

dimeric proteins which contain cysteine residues in their catalytic site which cleaves proteins

17
Q

what are the two mechanisms of apoptosis

A

extrinsic and intrinsic

18
Q

how is the extrinsic apoptosis pathway induced

A

death receptors

19
Q

what are the two ways intrinsic apoptosis pathway can be induced

A
  • mitochondrial stress (due to genotoxic damage drugs or growth factor removal)
  • genotoxic or ER stress (disrupted protein processing increased Ca ++)
20
Q

what is an apoptosome made up of

A

cytochrome c
apaf-1
pro-caspase 9

21
Q

what is BCL-2

A

(B-cell lymphoma/leukaemia-2)
it acts as a tumour suppressor

22
Q

what tumour suppressor can activate the intrinsic pathway

A

p53

23
Q

how does p53 activate the intrinsic pathway

A

it acts as a cellular stressor and initiates apoptosis through the transcriptional activation of BID and BAX (proapoptotic proteins)

24
Q

what is necrosis

A

cell death occurring in response to cell injury such as
- hypoxia
- temperatures extremes
- infection
- toxins

25
Q

what are the stages of necrosis

A

-swelling
cell rupture

26
Q

what occurs during the swelling stage of necrosis

A
  • organelle swelling
  • cell swelling
  • loss of ATP
27
Q

what occurs during the cell rupture stage of necrosis

A
  • disruption of cell integrity
  • plasma membrane rupture
28
Q

how does injured cells lead to increased mitochondrial permeability

A

-injured cells become depleted in ATP
- respiratory chain enzymes generate ATP due to the lack of oxygen (in situations like hypoxia)

29
Q

what are the 3 mechanisms in necrosis

A

1- ATP Depletion
2- reactive oxygen species (ROS)
3- Inactivation of H+ pumps

30
Q

what happens in the ATP depletion stage of necrosis

A

an increase in Na+ and H+
increased cytoplasmic Ca2+ in the mitochondrial matrix

31
Q

what happens in the reactive oxygen species (ROS) stage of necrosis

A

elevation of ROS results in opening of mitochondrial permeability transition pore (MPTP), mitochondrial swelling and rupture

32
Q

what happens in the inactivation of H+ pumps stage of necrosis

A

lysosomal pH declines, proteases are activated and released into the cytoplasm, digesting cytoskeletal proteins. osmotic imbalance leads to inflow of water into the cell leading to cell swelling and rupture.

33
Q

what is autophagy

A

its a self degradation process
- it also removes misfolded or aggregated proteins, clearing damaged organelles, as well as eliminating intra-cellular pathogens

34
Q

what is autophagy important for

A

for balancing sources of energy at critical times in development and in response to nutrient stress

35
Q
A

CHI (14 decks)

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