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
Voltage gated sodium channels are? 
Select and explain. 
A. Multimeric, B. Pentameric, C. Heterotrimer, D. Monomeric
C: Heterotrimer
Answer: C: Heterotrimer 
Explanation: Ans. is 'c' i.e., Heterotrimer lRef: Principles of medical physiology p. 24There are two different types of Sodium channels:-l) Voltage-gated sodium channel:These Are Present inExcitable cells.These exist as heterodimers or heterotrimers of alpha and beta subunits, containing one alpha and one or two betasubunits.2) Epithelial sodium channels:These are present in the epithelium of absorptive or secretory epithelium,e.g. colon, sweat gland duct, pancreatic duct, respiratory passage, and distal tubule of kidney.These exist as heterotetramers of alpha, beta and gamma subunits, containing mostly two alpha, one beta and one gamma subunits.