Insulin W3

Question 1

Insulin

Answer 1

main hormone involved in glucose metabolism

a peptide hormone

consists of 2 chains – α and β - linked by S-S bonds.

Acts at tyrosine kinase receptors

Secreted from β-cells in the endocrine pancreas into the hepatic portal vein

Question 2

Insulin synthesis

Answer 2

Synthesised by beta cells in the islet of Langerhans in the pancreas

Question 3

What is the major factor in control of insulin secretion?

Answer 3

level of blood glucose

This is a negative feedback loop

1. Blood glucose is increased
2. This is detected by beta cells in the pancreas.
3. Beta cells increase insulin secretion
4. Decreases blood glucose.
5. Decreases insulin secretion.

Question 4

other factors influencing secretion

Answer 4

1. Hormones i.e. GLP-1
2. Amino acid i.e. arginine
3. Fatty acids and ketone bodies.
4. Drugs i.e. sulfonylureas
5. Hormonal changes, i.e. cortisol.

Question 5

Actions of insulin

Answer 5

secreted following a meal due to increased BG

acts at tyrosine kinease coupled receptors

acts to decrease BG (and fatty acids and aminos)

Question 6

Major target organs

Answer 6

Liver

Skeletal muscles

Adipose tissue

Question 7

Liver and insulin

Answer 7

insulin is secreted into the hepatic portal vein

transports it directly to the liver.

Liver removes 60% of the insulin before it enters the systemic circulation

Question 8

Glucose Homeostasis

Answer 8

The process by which the body maintained blood glucose levels

Fed state = increase BG
Fast state = decrease BG

Question 9

Increased uptake of glucose is mediated by….

Answer 9

the insulin-dependant facilitated glucose transporter, GLUT-4

Question 10

What does glucose require to move through the plasma membrane

Answer 10

Transport proteins

Glucose is polar and hydrophilic so cant pass

Question 11

What does GLUT transporters allow

Answer 11

Facilitated diffusion of glucose down its conc grad

Question 12

What does GLUT-4 do in the presence of insulin

Answer 12

Moves from inside the cell to the cell membrane and therefore increases the uptake of glucose

Question 13

Where is GLUT-4 abundant

Answer 13

Skeletal muscle and adipose tissue

Question 14

Where is uptake by GLUT-2

Answer 14

Liver

Question 15

Action of insulin in fats and proteins

Answer 15

Lowers blood fatty acids and increases triglyceride synthesis

• increases fatty acid uptake into adipose tissues
• increases uptake of glucose into adipose where it is used for de novo synthesis of fatty acids and glycerides
• decreases lipolysis

Question 16

Action of insulin in fats and proteins - after meal

Answer 16

Lowers blood amino acids and increases protein synthesis
- increases uptake of amino acids into cells
- increase protein synthesis
- decrease protein degradation