Transmembrane proteins, Golgi, COP

Question 1

Endocytic pathways of protein sorting:

Answer 1

• Fully processed proteins are exported to the trans-Golgi network (TGN) and then sorted and delivered to their final destinations
• Fully processed proteins are exported to the trans-Golgi network (TGN) and then sorted and delivered to their final destinations.
• The transfer of vesicles from ER to Golgi, and between the Golgi sub-compartments, is achieved by coat proteins.

Question 2

Coat proteins have 2 functions:

Answer 2

1. Helps form the vesicle.
2. Helps select ‘cargo’ (i.e. Material inside or on vesicle)

Question 3

Coatomer: COPI and COPII

Answer 3

• COPI and COPII are protein complexes that assemble on the cytosolic surface of donor compartment membranes at sites where budding takes place.
• Coat protein complex = COP

○ COPI-coated vesicles move in retrograde direction.
○ COPII-coated vesicles move in anterograde direction.

-COPI and COPII are protein complexes that assemble on the cytosolic surface of donor compartment membranes at sites where budding takes place

• Electron micrographs reveal dense protein coat (COPI and COPII) on vesicles

Question 4

Endocytic pathways of protein sorting:

Answer 4

• Mucin secretion is an example of constitutive secretory pathway.
• On the other hand, the release of insulin and neurotransmitters is regulated

Question 5

Lysosome: Key features:

Answer 5

• Digestive organelles.
• Size: 25 nm to 1 μm.
• Internal pH of 4.6 (proton pump or H + -ATPase).
• Contains hydrolytic enzymes: acid hydrolases.
• Lysosomal membrane is composed of glycosylated proteins that act as a protective lining next to acidic lumen.