The Secretory pathway

Question 1

What is the secretory pathway?

Answer 1

Pathway from the ER to the cell surface & endosomal pathway

Question 2

What does the enzyme scramblase do?

Answer 2

Equilibrates lipids - scramblase catalyses flipping of phospholipid molecules

Question 3

What does the energy-dependent ‘flippase’ do?

Answer 3

Ensure membrane asymmetry is maintained

Question 4

What enzyme is used to transfer phosphatidylserine from the extracellular leaflet to the intracellular (cytotoxic) leaflet?

Answer 4

ATP-dependent translocase (flippase)

Question 5

What enzyme is used to transfer phosphatidylserine from the intracellular (cytotoxic) leaflet to the extracellular leaflet?

Answer 5

Scramblase

Question 6

What is the ER (endoplasmic reticulum) connected to?

Answer 6

Nuclear envelope

Question 7

What is the ER (endoplasmic reticulum) made up of?

Answer 7

ER forms hollow tubes & flattened sacs. The chambers are cisternae.

Question 8

What are the 2 types of ER (endoplasmic reticulum)?

Answer 8

• Rough ER (RER) outer membrane covered in ribosomes
• Smooth (SER) no ribosomes

Question 9

What are the 4 functions of the endoplasmic reticulum?

Answer 9

1. Quality control
2. Synthesis
3. Storage
4. Detoxification

Question 10

What molecules help newly synthesised linear sequences of amino acids to fold into tertiary & quaternary structures?

Answer 10

Chaperone proteins

Question 11

What is the smooth endoplasmic reticulum (SER) responsible for?

Answer 11

• phospholipid & cholesterol synthesis
• steroid hormone production
• synthesis & storage of glycerides
• synthesis & storage of glycogen
• important role as a calcium store

Question 12

What cells are responsible for Calcium signalling?

Answer 12

Acinar cells

Question 13

Describe the process of vesicular transport between the ER & Golgi apparatus

Answer 13

• vesicles bud off ER
• vesicle fuses to the Golgi

Question 14

What is the purpose of the coating of vesicles?

Answer 14

aids the formation of vesicles, however has to be discarded before vesicular fusion with the target compartment

Question 15

What are the 3 types of coating of vesicles?

Answer 15

• clathrin
• COPI
• COPII

Question 16

What is the function of SNAREs?

Answer 16

To aid vesicles reach the correct target

Question 17

What are the 2 types of SNAREs involved in vesicular transport?

Answer 17

v-SNAREs - vesicular SNAREs (found in the vesicle membrane)
t-SNAREs - target SNAREs (found in the membrane of the target membrane)

Question 18

What is the Golgi apparatus composed of?

Answer 18

flattened discs - cisternae (usually 5-6)

Question 19

What are the 3 primary functions of the Golgi apparatus?

Answer 19

• modification & packing of secreted proteins
• renewal & modification of the plasma membrane
• delivery of material to other organelles, especially the endocytic pathway

Question 20

What pathway transports plasma membrane & secreted proteins to the cell surface?

Answer 20

Constitutive secretory pathway in non-polarised cells

Question 21

What network is considered a major sorting station for newly-made proteins?

Answer 21

Trans-Golgi Network