Regulation Of Insulin Levels

Question 0

What is diabetes mellitus?

Answer 0

It is a disease in which blood glucose concentrations cannot be controlled effectively

Question 1

Explain how insulin secretion is controlled

Answer 1

• K+ ion channels are usually open, allowing K+ ions to diffuse out of the cell down a concentration gradient
• in high glucose concentrations, Glucose enters the B (beta) cells through a carrier protein that changes shape (facilitated diffusion) down a concentration gradient
• glucose is metabolised producing ATP (SYNOPTIC LINK - glycolysis, krebs and oxidative phosphorylation)
• high ATP concentration causes the K+ ion channels to close. The K+ ions build up inside the cell, making the inside of the cell more positive, depolarising the membrane
• the depolarisation causes voltage-gated Ca2+ ion channels to open, allowing Ca2+ ions to diffuse into the cell down a concentration gradient
• high concentrations of Ca2+ ions inside the cell cause the vesicles to move and fuse with the cell surface membrane, secreting the insulin by exocytosis

Question 2

What is hyperglycaemia?

Answer 2

When the blood glucose concentration is very high

Question 3

What is hypoglycaemia?

Answer 3

When the blood glucose concentration is very low

Question 4

Describe type 1 diabetes

Answer 4

• it is insulin dependent
• normally occurs in childhood
• can be cause by the immune system attacking the insulin producing b (beta) cells
• can be controlled with regular insulin injections and the careful management of diet and exercise

Question 5

Describe type 2 diabetes

Answer 5

• non insulin dependent
• mainly occurs in people over 40 but it is becoming more common in adolescents
• caused by glycoprotein receptors on the body cells losing their responsiveness to insulin or inadequate supply of insulin to the pancreas
• can be controlled by regulation of diet and exercise

Question 6

Discuss the use of insulin produced by genetically modified bacteria

Answer 6

• insulin used to be extracted from the pancreas of animals (usually pigs) as this matches human insulin most closely, but this had a number of problems
- had a low extraction efficiency
- risk of immune system rejecting the pig insulin
- moral and ethical issues
• however insulin can now be produced by genetically modified bacteria, this has a number of advantages
- there is less chance of rejection as human DNA coding is used in the genetic modification
- can be produced in batches more easily and quickly
- cheaper to manufacture insulin than extract it from animals

Question 7

Discuss the potential use of stem cells to treat diabetes mellitus

Answer 7

• recent research has shown that it may be possible to treat type 1 diabetes using stem cells
• stem cells are not yet differentiated and can be induced to develop into a variety of cell types
• scientists have recently found precursor cells in the pancreas of adult mice which are capable of developing into a variety of cell types
- if similar cells are found in the human pancreas then they could be used to produce new b (beta) cells in patients with type 1 diabetes