This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
The ligand-receptor complex dissociates in the endosome because: 
Select and explain. 
A. Of its large size, B. The vesicle looses its clathrin cost, C. Of the acidic pH of the vesicle, D. Of the basic pH of the vesicle
C: Of the acidic pH of the vesicle
Answer: C: Of the acidic pH of the vesicle 
Explanation: C i.e. Of the acidic pH of vesicle Endosomes and their role in receptor mediated Absorptive Ligand nPinocytosis:These are transient cellular structures involved in the transpo of macromolecules from the exterior of cells to its interior.They do not contain hydrolytic enzymes, are less dense than lysosomes and have an internal pH of 5.0.Endosomes receive the receptor-ligand complex by fusing with the 'coated vesicles'(Coated vesicles consist of Receptors, Ligand (macromolecule) and a layer of clathrin protein)On fusion, the coated vesicles discharge their macromolecules into the interior of endosomes.The low pH within the endosome, breaks the linkage * * Endosomebetween receptor-macromolecule coinplex and releases the receptor, the macromolecule, clathrin, and membrane fragmentsQ.