7.04 Type 1 Diabetes

Question 1

Insulin is synthesised by which cells?

Answer 1

Beta cells (Islets of Langerhans) in the pancreas

Question 2

How do beta cells secrete insulin?

Answer 2

They contain vesicles which are packed with insulin. Upon stimulation the vesicles move to the membrane and release the insulin

Question 3

Stimulus for insulin secretion

Answer 3

Rise in blood glucose levels (over 5mM)

Question 4

What does a rise in blood glucose levels do in the beta cells?

Answer 4

The increase in blood glucose levels causes uptake of glucose into the beta-cells via GLUT-2 transporter.

Question 5

What happens to glucose once it is in the beta cells?

Answer 5

It is metabolised by glycolysis and APT is generated. This causes inhibition of the ATP-sensitive K+ channels on the membrane, causing depolarisation and increased Ca into the cell. The increase of Ca releases insulin from the cell.

Question 6

What does insulin do?

Answer 6

It stimulates the uptake of glucose into tissues (especially the brain), including muscle and adipose tissue. It decreases gluconeogenesis in the liver.

It inhibits lipid degradation and protein degradation.