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MCB2050 > o. Lecture (Feb. 15th) Slide Deck > Flashcards

o. Lecture (Feb. 15th) Slide Deck Flashcards

1
Q

What is the difference b/w a cell death due to apoptosis vs a cell death due to necrosis?

A

apoptosis first degrades the inner components w/in the cell while the mem remains intact. Then is engulfed by macrophage. Thus allowing the components w/in the cell to be recycled

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2
Q

What are the two things that trigger apoptosis?

A
  1. deregulation of the cell cycle
  2. DNA damage
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3
Q

Describe the 2 types of cell death

A
  1. apoptosis = programmed cell death in which the inner components are dismantled and packed into apoptotic bodies w/out rupturing the mem. Followed by the apoptotic bodies being absorbed and recycled by macrophage
  2. necrosis = when the cell mem ruptures causing he cellular contents to pour out
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4
Q

What is this an image of?

A

necrosis

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5
Q

What is this an image of?

A

apoptosis

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6
Q

Describe the apoptotic process in 5 steps

A
  1. the apoptotic signal is triggered due to some dysregulation
  2. the cytoplasm condenses
  3. the nuclear envelope breaks up causing nuclear fragmentation
  4. all of the fragmented components are packaged into apoptotic bodies where they are blebbed
  5. the apoptotic bodies undergo phagocytosis (are engulfed) by a phagocytic cell where the components are degraded and recycled
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7
Q

How much DNA do cells have when they go through the following stages? Explain
a) G1
b) G2
c) apoptosis

A

a) one copy as the cell has yet to be synthesized/replicated
b) 2 copies as the cell has already undergone DNA synthesis/replication
c) <1 copy as the DNA of the cell has been degraded and packed randomly into different apoptotic bodies waiting to be degraded and recycled

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8
Q

How was it proven that cells undergoing apoptosis have fragmented DNA?

A

When placing a normal cell vs a cell undergoing apoptosis in gel electrophoresis the normal cell clustered at the top had trouble traveling down the gel while the apoptotic cell was able to. Meaning despite these being the same type of cells the one undergoing apoptosis must have fragmented the DNA allowing for it the travel down the gel

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9
Q

how many base pairs are b/w nucleosomes?

A

~200bps

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10
Q

What cleaves the DNA into fragments during apoptosis?

A

nucleases

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11
Q

a) what model organism was used to discover apoptosis?
b) What did S. Brenner discover?
c) What did R. Horvitz discover?

A

a) C. elegans - tiny transparent worms
b) that out of all the cells produced during development 131 cells were doomed to die via apoptosis
c) discovered the cell death genes responsible for apoptosis

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12
Q

What is the significance of the following genes?
a) ced-1 gene
b) ced-3 gene

A

a) allows apoptotic cell bodies to under phagocytosis
b) pro-apoptotic gene = allows a cell to undergo apoptosis

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13
Q

a) What are caspases?
b) Describe the 3 types of caspases
c) Match the following examples of caspases w/ the types you provide
1. caspase-3
2. caspase-6
3. caspase-7
4. caspase-8
5. caspase-9

A

a) Cysteinyl asparate-specfici proteinase
b)
- initiator caspases = process and activate effector caspases (4 + 5)
- executioner caspases = cleave specific cellular proteins leading to apoptosis (3, 6, 7)
- effector caspases = digest the proteins of the cell and activate nucleases that degrade the DNA

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14
Q

Which organelle plays the biggest role in the regulation of caspases?

A

the mitochondria

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15
Q

Describe the two ways to regulate cell death in vertebrates

A
  1. through the intrinsic death pathways which are activated by proteins in the mitochondria as a response to cell stress/DNA damage
  2. through the extrinsic death pathways which are activated by activating the death receptors via direct contact by other cells telling them to undergo apoptosis
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16
Q

a) what activates the intrinsic death pathway? - 2
b) What regulates this? - 2

A

a) the release of Cyt C from the mitochondria
b) this is regulated by the pro-apoptotic and anti-apoptotic proteins

17
Q

What are the 3 pro-apoptotic proteins?

A
  1. Bak
  2. Bax
  3. Boc
18
Q

What are the 2 pro-survival proteins?

A
  1. Bcl-2 and Bcl-1
19
Q

a) What are the 3 BH3-only proteins?
b) What does this protein regulate?
c) Why is it called the BH3-only protein?

A

a) Bad, Bim, and Puma

20
Q

a) What are the 3 BH3-only proteins?
b) What does this protein regulate?
c) Why is it called the BH3-only protein?

A

a) Bad, Bim, and Puma
b) regulates pro-survival proteins = proteins that inhibit apoptosis
c) its a protein that only contains the BH3 domains

21
Q

What are the 3 members of the Bcl-2 family of proteins

A
  1. pro-survival member
  2. pro-apoptotic members
  3. BH3-only members
22
Q

Pro-survival members and pro-apoptotic proteins.
a) what do they have in common?
b) what differentiates them?

A

a) control the transport of Cyt C through the outer mitochondrial mem
b)
- Pro-survival =prevent the formation of the pores suppressing the influx of Cyt C
- pro-apoptotic = forms the pores allowing an influx of Cyt C

23
Q

What is this image showing?

A

pro-survival member

24
Q

What is this image showing?

A

pro-apoptotic member

25
Q

a) What is this image showing?
b) what is the section on the right?

A

a) BH3-only protein
b) a hydrophobic domain

26
Q

for the intrinsic death pathway describe the fxn of the following
a) Bak or Bax
b) Bcl-2 or Bcl-x
c) Bad, Bim, Puma (general)

A

a) pro-apoptotic proteins that form the pore on the mitochondrial membrane allowing Cyt C to enter the cytosol
b) pro-survival proteins that bind to the pro-apoptotic proteins to prevent the formation of the pore keeping the Cyt C in the intermembrane space
c) BH3-only proteins that allow pro-apoptotic proteins to disassociate from the pro-survival proteins in order to form the pore

27
Q

Once the pore is formed and the Cyt C is released into the cytosol of the mitochondria What are the next 4 steps that result in cell death?

A
  1. the Cyt C binds to Apaf activating it
  2. the protease Apaf cleaves off the inhibitory section transforming procaspase-9 to the active caspase-9
  3. the executioner caspase caspase-9 cleaves off the inhibitory section of procaspase-3 transforming it into the active caspase-3
  4. caspase-3 cleaves the substrates w/in the cell eventually leading to cell death
28
Q

Which of the following BH3-only proteins are originally found in the nucleus?
a) Puma
b) Bad
c) Bim
d) none of them
e) all of them

A

a

29
Q

Describe the 3 steps in the intrinsic death pathway that involves the BH3-only protein Bad to prevent apoptosis

A
  1. trophic factors bind to the trophic factor receptor which dimerizes and autophosphorylates
  2. This RTK phosphorylates PI-3 kinase which phosphorylates PKB
  3. the active PKB phosphorylates Bad causes it to bind to the inhibitory protein 14-3-3
30
Q

Normally the BH3-only protein Puma remains in the nucleus so how can it help the pro-apoptotic proteins disassociate from the pro-survival proteins?

A

the presence of DNA damage activates nuclear exportins which translocate Puma out of the nucleus allowing it to directly interact w/ the regulator proteins

31
Q

What triggers the release of the BH3-only protein Bim?

A

when the cytoskeleton of the cell becomes extremely disrupted it disassociates from the cytoskeleton and influences the regulatory apoptotic proteins

32
Q

Describe the 5 steps for the extrinsic death pathway

A
  1. the death signals bind to the death receptor, TNF
  2. TNF binds to TRADD and FADD activating them
  3. TRADD and FADD cleaves the inhibitory section of procaspase-8 transforming it into the active caspase-8
  4. Caspase-8 activates the executioner caspases, caspase-3, 6, and 7 through the same method
    5.. the executor caspases cause cell death

MCB2050 (18 decks)

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