This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Transpo Processes, Subject name: Physiology
Peripheral cell membrane proteins are: 
Select and explain. 
A. Carriers, B. Channels, C. Enzyme, D. Receptors
D: Receptors
Answer: D: Receptors 
Explanation: There are two types of cell membrane proteins: Integral proteins - protrude all the way through the membrane Peripheral proteins - attached only to one surface of the membrane and do not penetrate all the way through. Integral proteins acts as: Channels carriers enzymes cell adhesion molecule Peripheral proteins acts as: Receptors cell adhesion molecules (CAMs) sub membranous cytoskeleton: ankyrin is a peripheral membrane protein that anchors the spectrin-actin meshwork directly to an integral membrane protein of the erythrocyte