Question

1. a) What is the molecule responsible for the release of transport vesicles and describe its function in the endocytosis of LDL via LDL receptors.

b) Comment on how inhibition of the molecule identified in (a) affects uptake of LDL into the cell.

2. Describe the three stages of clathrin-coated vesicle formation including the type of proteins involved? You may use diagrams to explain or enhance your answer.

Answer 1

Ans 1 a: Molecule that are responsible for the release of transport vesicles are called as Clathrin. These proteins are important for the shape and formation of vesicles. Clathrin have three “legs” which forms a cage like structure around the membrane vesicles for transportation. LDL helps in the transportation of the cholesterol to different cells within the body. LDL receptors are found on the surface of the cell that binds the LDL complex for starting the endocytic process.

Ans 1 b:) Endoplasmic Reticulum (ER) synthesizes the LDL receptors and then transport them in the Golgi Body. When the LDL receptor is attached with the LDL complex, clathrins start the process. The receptors join together forming clathrin-coated pits. The coated pits are strained off and forms endocytic vesicles, and then uncoat itself. After uncoating, the vesicle is transported to an endosome. Endosome have low PH which releases the LDL particles. These particles then reaches to lysosome for degradation, which releases the cholesterol into the cell.

Ans 2: Diagram:

The three stages are: Initiation, Assemby/Maturation and Fission