Lecture 9

Question 1

Parts of N - Glycosylation

Answer 1

• 2 NAG
• 9 Mannose
• 3 Glucose

Question 2

Core segment of N Glycocylation

Answer 2

• Dolichol phosphate
• Embedded in the ER membrane

Question 3

Steps of N - Glycosylation

Answer 3

• Core segment assembled on lipid carrier called dolichol phosphate which is embedded in the ER
• Sugars are addes to dolichol phosphate one by one by glycotransferases
• 2 NAG 9 Mannose 3 Glucose: Total 14 sugars
• Oligosacchryl tranferase helps it bind to aspargine

Question 4

Quality control of Glycosylation

Answer 4

• Gradual removal of CHO
• Binds to molecular chaperone : Calnexin
• Glucosidase 2 removes the final terminal glucose
• Glycoprotein folding then assessed by a conformation sensing enzyme called UGGT protein

Question 5

Cis face of golgi

Answer 5

Faces ER

Question 6

Trans face of golgi

Answer 6

Opposite side of stack

Question 7

Cis Golgi network

Answer 7

• Sorting station
• Back to ER
• Go to trans golgi

Question 8

Trans golgi netwoek

Answer 8

Packaging to different organelles

Question 9

Vesicular transport model

Answer 9

Model of transport from cis to trans

Question 10

Cisternal maturation model

Answer 10

Cisternae moves as it matures from cis or trans

Question 11

Golgi cisternae move in _____ fahsion

Answer 11

Anterograde

Question 12

Vesicles move in a ____ fahsion

Answer 12

Retrograde

Question 13

COP 2

Answer 13

Move forward
ER to Golgi

Question 14

COP 1

Answer 14

Backward
Trans to cis to ER

Question 15

Clathrin

Answer 15

TGN - Endosomes and lysosomes

Question 16

COP 2 - Coated Vesicles

Answer 16

• ER exit sites
• EX export signals
• Proteins transported by COP 2 coated vesicles

Question 17

What are the proteins transported by COP2 Coated vesicles

Answer 17

• Glycotransferases to Golgi
• Vesicle docking proteins
• Cargo selecting proteins

Question 18

Clathrin Coated Vesicles

Answer 18

• Trans Golgi network to endosomes and lysosomes

Question 19

Sar 1

Answer 19

G protein required
- Requires COP 2 proteins and Cargo receptors
- It is all coated

Question 20

Where do COP 2 coated vesicles bud

Answer 20

ER exist sites (ERES)

Question 21

Steps of COP2

Answer 21

• Sar protein binds to GDP and binds to ER membrane
• Induces a wedge
• Sec 23 and 24 forms a complex and binds with cargo: Increase the curvature of the vesicle
• Sec 31 increase the curvature furthur more

Question 22

Two layers of Transport Vesicles

Answer 22

1. Outer scafold
2. Inner layer

Question 23

Structure of clatherin

Answer 23

• Outer scaffold structures
• ## Three legged complexes

Question 24

2 mechanisms of maintainace of membrane composition

Answer 24

• Retention
• Retrieval