Question

When glucose enters a pancreatic beta cell, it is broken down and triggers a cascade of events leading to insulin production and secretion. Describe the steps involved. Bullet points with no description will only receive partial grade.

Answer 1

Beta cells are the site of insulin synthesis and secretion. Insulin is secreted when the blood glucose levels are high. Insulin promotes glycogenesis (formation of glycogen from glucose) and thus decreases blood glucose levels.

steps involved in activation of insulin production are.

1. Glucose is detected by GLUT2 ( glucose transporter 2) receptors present on Beta cells. GLUT2 brings glucose from the blood stream inside the beta cell.
2. the glucose undergoes glycolysis inside the cytoplasm (breakdown of 1 glucose into 2 pyruvate molecules). The pyruvate then moves to the mitochondria and undergoes kerbs cycle and ETC. all this process involved in breakdown of glucose leads to release of ATPs,

3, increased concentration of ATP in the cytoplasm leads to disruption of ligand gated potassium channels. As K+ channels are closed the positive charge inside the cell increases and membrane potential gets depolarised.

4. depolarisation of the membrane potential leads to opening of voltage gated calcium ion channels.

5. increase in the calcium concentration in the cell triggers fusion  of insulin containing vesicles with the plasma membrane leading to release of insulin in the blood stream.

this insulin then circulate the blood and induced liver cells to uptake glucose and convert it into glycogen.