Question

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.

Answer 1

a). receptor mediated endocytosis is the process of transport of various extra cellular nutritional and regulatory molecules in to the target cell through plasma membrane receptors. In many systems, the receptor cluster forms a coated pits on the surface of plasma membrane, these coated pits are invaginates into the target cell to form endocytic vesicles. The extra cellular ligand enclosed in the endocytic vesicle is delivered to intracellular sites. Mostly these are delivered to lysosomes where, they undergo degradation.

The extracellular ligand molecules are responsible for the release of transport vesicles, and plasma low density lipoproteins (LDL). These ligand molecules deliver the low density lipoproteins to lysosomes where LDL molecules are degraded and cholesterol is released and used for the synthesis of membranes, steroid hormones and bile acids.

The delivery of low density lipoproteins (LDL) VIA LDL receptors to lysosomes through endocytosis in order to release cholesterol for the synthesis of membranes and steroids is the main function of extracellular ligand molecules.

b). Uptake of LDL into the cell is inhibited by the surface receptors on the cell membrane.