12 - Princples of Vesicular Transport

Question 1

How is transport mediated?

Answer 1

Through vesicles

Question 2

How do materials move in and out of the cells?

Answer 2

They move throught the cell in an anterograde action (forward) and out of the cell in a retrograde action.

Question 3

How do vesicles move from the ER to the Golgi?

Answer 3

They bud off the ER and move to the gogi where it fuses to the membrane.

Question 4

What are 3 essential components for vesicle formation?

Answer 4

• GTPase
• Adaptor protein (to recognise the cargo)
• Coat protein

Question 5

What are small GTPases?

Answer 5

Molecular switches.

Question 6

What is the founding member of the GTPase family?

Answer 6

Ras

Question 7

When are the small GTPases active?

Answer 7

When they are bound to GTP.

Question 8

When are small GTPases inactive?

Answer 8

When they are bound to GDP.

Question 9

How is the GDP converted to GTP?

Answer 9

By guanine exchange factors (GEFs)

Question 10

How are the molecules inactivated from GTP to GDP?

Answer 10

By the action of GTPase activating proteins. (GAPs)

Question 11

What are COPII coated vesicles?

Answer 11

Vesicles that form at the exit sites of the ER.

Question 12

What are the components of COPII coated vesicles?

Answer 12

• GTPase - Sar1 (Arf family)
• Adaptor - Sec23/24
• Coat - Sec13/31

Question 13

How are COPII vesicles formed?

Answer 13

• Cargo is recognised by the adaptor
• Sar1 GTPase is activated.
• Sec23/24 adaptor complex allows the outer protein coat to be recruited.
• The bud is formed and then pinches off to form vesicles.

Question 14

What helps us understand what makes a COPII vesicle?

Answer 14

Reconstitution experiments.