Describe the process of insulin secretion. (7 marks)

Beta cells have vesicles containing insulin inside them (1). (2) High glucose levels cause glucose uptake via glucose channels into the beta cell and glucose is metabolised into ATP (3) inside the cell, which causes K+ channels to be blocked. This causes cell membrane depolarisation (4) which leads to calcium channels opening (5). Ca2+ enters into the cell via diffusion (6) which results in ex0cytosis of vesicles containing insulin (7) from the beta cell.