This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Which of the following is not an integral protein 
Select and explain. 
A. Pump, B. Insulin Receptor, C. G-Protein coupled receptors, D. Enzyme receptors
D: Enzyme receptors
Answer: D: Enzyme receptors 
Explanation: Ref:Ganong's Review of Medical physiology 26th edition Pgno: 35 Enzyme receptor is a peripheral protein Peripheral proteins are either inside or outside of the membrane Proteins in the Plasma membrane Integral Proteins Peripheral Proteins Are Transmembrane proteins i.e., They span the thickness of the membrane Are present either on the inner or outer surface of the membrane Includes Insulin receptor, pumps, transpo proteins (carrier), receptors (eg., G-Protein coupled receptors) Includes receptors (eg- Cell surface receptors) and enzymes