Glucose homeostasis

Question 1

What are the exocrine cells in the pancreas?

Answer 1

Acinar cells that secrete enzymes that are passed into the duodenum.

Question 2

What are Islet of Langerhans?

Answer 2

Groups of pancreatic cells secreting insulin and glucagon.

Question 3

What is the difference between alpha and beta cells in the islets of Langerhans?

Answer 3

Alpha cells secrete glucagon whereas beta cells secrete insulin.

Question 4

What effect does insulin have on the plasma?

Answer 4

It decreases glucose, amino acids and free fatty acids.

Question 5

What effect does glucagon have on the plasma?

Answer 5

It increases glucose and ketones.

Question 6

What do delta cells do?

Answer 6

Produce and release somatostatin which suppresses GI motility and the release of insulin and glucagon.

Question 7

What is the structure of insulin?

Answer 7

It is made up of an A chain (21 a.a), a B chain (30 a.a) and a c chain. The c-peptide is inactive.

Question 8

What is insulin degraded by?

Answer 8

Insulinase in the liver and kidneys.

Question 9

When is insulin released?

Answer 9

In response to changes in glucose/ATP.

Question 10

How is insulin secreted?

Answer 10

It occurs via a calcium-dependent exocytosis.

Question 11

What happens when insulin binds to the insulin receptor?

Answer 11

There is dimerization, autophosphorylation that causes effects on intracellular kinases and following effects on key enzymes.

Question 12

What effect does insulin have on carbohydrate metabolism?

Answer 12

It facilitates the entry of glucose into muscle, it stimulates the liver to store glucose as glycogen and decreases the concentration of glucose in the blood.

Question 13

What effect does insulin have on lipid metabolism?

Answer 13

It promotes the synthesis of fatty acids in the liver (when glycogen is saturated) which leads to an increase in lipoproteins in the circulation to release fatty acids. It inhibits the breakdown of fat in adipose tissue and promotes glycerol synthesis from glucose and increases triglyceride synthesis.

Question 14

How does insulin cause cells to take up glucose?

Answer 14

When released, it causes glucose transporters to be released from storage microsomes and migrate to the cell membrane. Glucose can then be taken up by the cell.

Question 15

When happens when glucose is taken up by muscle cells?

Answer 15

It is converted into glucose-6-P which is then converted into lactic acid, releasing energy.

Question 16

What happens when insulin acts on the liver?

Answer 16

It causes glucose-6-P to be converted to glycogen, as well as it combining with lactic acid, amino acids and fatty acids to form lipoproteins.

Question 17

What effect does insulin have on adipose tissue?

Answer 17

It causes amino acids, glucose and lipoproteins (from the liver) to be taken up and converted into triglycerides.

Question 18

What happens if glucose levels rise above the normal?

Answer 18

The homeostasis is disturbed and beta cells release insulin. This causes an increased rate of glucose uptake, increased glycogenesis, increased protein and fat synthesis.

Question 19

What is the normal glucose level in the blood?

Answer 19

70-110mg/dl.

Question 20

How many amino acids is glucagon made up of?

Answer 20

29.

Question 21

What does glucagon stimulate?

Answer 21

Glycogenolysis, gluconeogenesis and increases the breakdown of fats.

Question 22

What is the body’s response if glucose levels fall below normal?

Answer 22

The homeostasis is disturbed, alpha cells release glucagon which causes increased glycogenolysis, fats to fatty acids, protein breakdown and increased gluconeogenesis.

Question 23

What is hypoglycaemia?

Answer 23

When the blood glucose is below the normal level (3mM).

Question 24

What are some of the effects of hypoglycaemia?

Answer 24

Impaired vision, slurred speech, staggered walking, mood change, confusion, coma and death.

Question 25

What is hyperglycaemia?

Answer 25

Diabetes mellitus - blood glucose is above the normal level.

Question 26

What are risk factors and features of type 1 diabetes?

Answer 26

Family history, genetics, infection. It appears suddenly and is incurable.

Question 27

What are the risk factors and features of type 1 diabetes?

Answer 27

Body weight, inactivity, family history, age. It can go undiagnosed or unnoticed for years and can be cured with diet and lifestyle changes.

Question 28

What is gestational diabetes?

Answer 28

It is associated with pregnancy and poses serious risks to the mother and child. There is an increased risk of developing type 2 diabetes due to it.

Question 29

What type of hormone is glucagon

Answer 29

1. Peptide hormone