25. Coated Vesicles

Question 1

Coated Vesicles

Answer 1

Receptors for many substances, such as LDLs/protein hormones, are integral proteins of the cell membrane.

Binding of the ligand to its receptor spreads the receptors.

• The electron dense coating on the cytoplasmic surface of the membrane is composed of several polypeptides (clathrin).
• In developing coated pits, clathrin molecules interact - forming that region of cell membrane into a cage-like invagination - pinched off into the cytoplasmic surface = coated vesicle carrying the ligand and its receptor.
• Coated vesicles are a cell’s way of receiving contents from outside the cell
• Membrane coat proteins receive ligands from outside of the cell = receptor ligand complexes.
• These then build up on the cell membrane forming a ‘Coated Pit’ with the ligands and receptors together.
• These coated pits poses an electron dense coating on the cytoplasmic surface (Clathrin)
• These pits become deeper until the membrane pinches them off into the cytoplasm as a coated vesicle containing the ligands and their receptors internally
• They then fuse with the endosomal compartment (a dynamic system of membranous vesicles designed for this purpose).
• Then both protein receptors and clathrin molecules are recycled back to CM - participate in the formation of new coated pits.