Physiology and pathophysiology of insulin and glucagon

Question 1

Which protein allows glucose to enter Beta cells of the pancreas?

Answer 1

GLUT-2

• a glucose transporter

Question 2

How do beta cells become depolarised once glucose has entered them?

Answer 2

Glucose undergoes glycolysis to produce ATP

ATP sensitive K+ channels close

Stops K+ from flowing out of cell

Beta cell depolarise

Question 3

What does depolarisation of the beta cell cause?

Answer 3

Allows voltage gated Ca2+ channels to open causing a Ca2+ influx

This activates phospholipase C, which cleaves a substance to make IP3

Question 4

When IP3 binds to plasma membrane receptor proteins of the endoplasmic reticulun, what happens?

Answer 4

Ca2+ released causing insulin secretion

Question 5

How is does insulin cause the cells of the body to uptake glucose?

Answer 5

Insulin binds to alpha unit of cell receptor which activates kinase of the beta-unit (intracellular part of receptor)

This causes phosphorylation of IRS-protein which causes acitvation of cascades

• GLUT-4 to membrane and influx of glucose into cell
• PKB which causes increased glycogen synthesis

Question 6

What is the incretin effect?

Answer 6

GI hormones stimulate a release of inslin from Beta cells when glucose passes through the GI tract resulting in plasma glucose levels being decreased

• e.g. GLP-1

Question 7

What is GLUT-4 protein?

Answer 7

A glucose receiver and transporter in cells of the body

Question 8

What does CAPN-10 protein do?

Answer 8

Causes break down of fat

Question 9

What is IRS-1 protein?

Answer 9

A protein that when phosphorylated in cells of the body causes a cascade which results in glucose influx into cell