<prompt> Which of the following ion plays a role in exocytosis?SodiumPotassiumCalciumMagnesium  <response>: Ans. C CalciumRef: Ganong 25th edition, P 46 Exocytosis is a calcium dependent process where vesicles containing material for export are targeted to the cell membrane. This area of fusion then breaks down leaving the contents of vesicle outside the cell membrane intact. The reverse of exocytosis is called as endocytosis and is mediated by the protein Clathrin. 