Glucose Potassium Channels Ions Cell Insulin Blood Diffuse

1. At normal blood glucose concentrations potassium channels in the plasma membrane of beta cells are open and potassium ions diffuse out of the cell. The inside of the cell is at a potential of -70mV with respect to the outside.

2. When blood glucose concentration rises, glucose enters the cell by a glucose transporter.

3. The glucose is metabolised inside the mitochondria, resulting in the production of ATP.

4. The ATP binds to potassium channels and causes them to close. They are known as ATP-sensitive potassium channels.

5. As potassium ions can now no longer diffuse out of the cell, the potential difference reduces to around -30mV and depolarisation occurs.

5. Depolarisation causes the voltage-gated calcium ion channels to open.

6. Calcium ions enter the cell and causes secretory vesicles to release insulin they contain by exocytosis.