Lecture 12 Flashcards

1
Q

What is essential for proper functioning cell?

A

protein degradation

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1
Q

What are some characteristics of protein degradation?

A
  • highly controlled
  • can be used as a way of regulation
  • is executed bu proteases
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2
Q

Where are transmembrane proteins degraded?

A

lysosome

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3
Q

Where are cytoplasmic proteins degraded?

A

the proteosome

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4
Q

What is ubiquitin? Ub

A

small 76aa protein

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5
Q

What is the function of Ub?

A

a tag in protein degradation

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6
Q

Where is the C-terminus of Ub covalently linked to?

A

lysine side chainof proteins that suppose to be degraded

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7
Q

What are poly Ub chains?

A

proteins destined for degradation are often tagged not only by a single Ub but by poly Ub

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8
Q

What is E1

A

ubiquitin activating enzyme

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9
Q

What is E2

A

Ubiquitin-conjugating enzyme

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10
Q

What is E3

A

ubiquitin ligase

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11
Q

What are proteasomes?

A

large protein complex that degrades poly ubiquitinated proteins

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12
Q

How does the proteasome degrade the polyubquitinated protein?

A
  • the cap unfolds the protein and feed the protein into the core
  • the core cleaves the protein into small peptides
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13
Q

What is the proteasome responisble for?

A

the degradation of soluble proteins both in cytoplasm and nucleus

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14
Q

What happens in the MVB pathway?

A
  • cell surface protein x is ubiquinated
  • x-Ub is sorted in clathrn-coated vesicles and endocytosed
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15
Q

What is the X-Ub sorted by at the MVB?

A

ESCRT in the intralumenal vesicles

16
Q

What happens after the X-Ub is sorted by the ESCRT?

A
  • the MVB fuses with the lysosome and delivers the vesicles into the lumen of the lysosome
  • the lysosome degrades the vesicles with their content (protein x)
17
Q

How many ESCRT complexes are there?

18
Q

Characteristics of ESCRT?

A

soluble cytoplasmic protein complexes

19
Q

After being recruited by MVB, what happens to the ESCRT?

A

assembles into a machine that sort ubiquinated cargo and forms vesicles

20
Q

What happens during ESCRT vesicle formation?

A

the membrane deforms away from the cytoplasm, even though the ESCRTs localize to the cytoplasmic face of the endosome

21
Q

What is unique about ESCRT vesicles?

A

reversed topology

22
Q

What happens to the membrane when the endocytic vesicles form with the help of a cthrn coat?

A

membrane deforms towards the cytoplasm

23
Q

Where are MVB vesicles and their content degraded?

A

in the lysosome

24
What is Autophagy?
degradation of large particles and structures
25
What is autophagy induced by?
starvation
26
Why does starvation cause autophagy?
starvation causes degradation of cytoplasmic protein by autophagy which release amino acids important to survive the starvation conditions
27
How many membranes do autophagosoms have?
2 membranes
28
What do autophagosomes fuse with?
The lysosome and the content degraded
29
Steps of mitophagy?
- double membrane surround organelle - organelle containing autophagosome fuses with lysosome
30
Autophagosome deliver their content to the ----
lysosome
31
What is the phase responsible for cell division?
M pahse
32
What phases are part of interphase?
G1 + S + G2
33
What are the responsibility of CDKs?
Phosphorylate proteins that are responsible for initiating and regulating the major events of the cell cycle
34
How are CDKs activated?
By binding to cyclin
35
What are cyclin ubiquinated and degraded by?
proteosome