Lecture 12

Question 1

What is essential for proper functioning cell?

Answer 1

protein degradation

Question 1

What are some characteristics of protein degradation?

Answer 1

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

Question 2

Where are transmembrane proteins degraded?

Answer 2

lysosome

Question 3

Where are cytoplasmic proteins degraded?

Answer 3

the proteosome

Question 4

What is ubiquitin? Ub

Answer 4

small 76aa protein

Question 5

What is the function of Ub?

Answer 5

a tag in protein degradation

Question 6

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

Answer 6

lysine side chainof proteins that suppose to be degraded

Question 7

What are poly Ub chains?

Answer 7

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

Question 8

What is E1

Answer 8

ubiquitin activating enzyme

Question 9

What is E2

Answer 9

Ubiquitin-conjugating enzyme

Question 10

What is E3

Answer 10

ubiquitin ligase

Question 11

What are proteasomes?

Answer 11

large protein complex that degrades poly ubiquitinated proteins

Question 12

How does the proteasome degrade the polyubquitinated protein?

Answer 12

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

Question 13

What is the proteasome responisble for?

Answer 13

the degradation of soluble proteins both in cytoplasm and nucleus

Question 14

What happens in the MVB pathway?

Answer 14

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

Question 15

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

Answer 15

ESCRT in the intralumenal vesicles

Question 16

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

Answer 16

• 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)

Question 17

How many ESCRT complexes are there?

Answer 17

5

Question 18

Characteristics of ESCRT?

Answer 18

soluble cytoplasmic protein complexes

Question 19

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

Answer 19

assembles into a machine that sort ubiquinated cargo and forms vesicles

Question 20

What happens during ESCRT vesicle formation?

Answer 20

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

Question 21

What is unique about ESCRT vesicles?

Answer 21

reversed topology

Question 22

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

Answer 22

membrane deforms towards the cytoplasm

Question 23

Where are MVB vesicles and their content degraded?

Answer 23

in the lysosome

Question 24

What is Autophagy?

Answer 24

degradation of large particles and structures

Question 25

What is autophagy induced by?

Answer 25

starvation

Question 26

Why does starvation cause autophagy?

Answer 26

starvation causes degradation of cytoplasmic protein by autophagy which release amino acids important to survive the starvation conditions

Question 27

How many membranes do autophagosoms have?

Answer 27

2 membranes

Question 28

What do autophagosomes fuse with?

Answer 28

The lysosome and the content degraded

Question 29

Steps of mitophagy?

Answer 29

- double membrane surround organelle - organelle containing autophagosome fuses with lysosome

Question 30

Autophagosome deliver their content to the ----

Answer 30

lysosome

Question 31

What is the phase responsible for cell division?

Answer 31

M pahse

Question 32

What phases are part of interphase?

Answer 32

G1 + S + G2

Question 33

What are the responsibility of CDKs?

Answer 33

Phosphorylate proteins that are responsible for initiating and regulating the major events of the cell cycle

Question 34

How are CDKs activated?

Answer 34

By binding to cyclin

Question 35

What are cyclin ubiquinated and degraded by?

Answer 35

proteosome