What are membrane bound receptors?

When protein membrane receptors are activated, what usually happens?

• a.A change occurs on only one membrane surface: exterior or interior. b.The receptor changes conformation after binding with signal polypeptides. c.The receptor preferentially binds with lipid or glycolipid signal molecules. d.The receptors open and close in response to protein signals. e.A change occurs in intracellular ion concentration.

• Answer:

  Based on the choices your best answer seems to be B. Choice A has nothing to do with the actual protein receptor itself, just the membrane so that one is out. Choice C is too specific for activation because protein membrane receptors can bind to a diverse number of ligands and not just lipids or glycolipids. These receptors show preference based on the type of signaling they create in the cell. Choice D indicated both inactivation and deactivation, which isn't what the question is asking since it wants to know what happens upon activation. And choice E is specific to ion channel membrane proteins which is once again, too specific and ignores too many other membrane receptors. Choice B is correct because upon binding of any substrate ALMOST ALWAYS causes a conformational change to occur in the receptor protein.