This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and Reproduction, Subject name: Physiology
A small ca+2 binding protein that modifies the activity of many enzymes and other proteins in response to changes of ca2+ concentration, is known as 
Select and explain. 
A. Cycline, B. Calmodulin, C. Collagen, D. Kinesin
B: Calmodulin
Answer: B: Calmodulin 
Explanation: Ans. (b) Calmodulin(Ref: Ganong, 25th ed/p.55)Once inside the cell, Calcium binds with calmodulin.This calcium - calmodulin complex activates an enzyme called calmodulin dependent protein kinases that phosphorylates many downstream effector proteins