Unit 6 - 3.6.4.2 Control of blood glucose concentration

Question 1

Why is glycogen a ideal storage molecule for glucose?

Answer 1

Highly branched so can be hydrolysed rapidly to release glucose.
Osmotically inactive so does not cause osmosis of water into or out of cells.
Compact so many glucose molecules can be stored in a small space of a cell.

Question 2

Define homeostasis.

Answer 2

Homeostasis is the maintenance of a stable internal environment within restricted limits.

Question 3

Define glycogenesis.

Answer 3

Glycogenesis is the process of converting glucose to glycogen for storage in the liver and muscle cells, stimulated by insulin binding to the cell surface protein receptor.

Question 4

Define glycogenolysis.

Answer 4

Glycogenolysis is the hydrolysis of glycogen into glucose, stimulated by glucagon and adrenaline binding to cell surface protein receptors when blood glucose levels are low.

Question 5

Define gluconeogenesis.

Answer 5

Gluconeogenesis is the synthesis of glucose from non-carbohydrate sources, such as amino acids and glycerol

Question 6

Describe the role of insulin in lowering blood glucose concentration.

Answer 6

Insulin promotes glucose uptake by stimulating the introduction of glucose carrier proteins in the cell membranes and stimulates glycogenesis, lowering blood glucose concentrations.

Question 7

Describe how glucagon increases blood glucose concentration.

Answer 7

Glucagon triggers glycogenolysis and gluconeogenesis in the liver, releasing glucose into the bloodstream to raise blood glucose concentrations.

Question 8

Describe the process of glycogenolysis and its role in glucose regulation.

Answer 8

Glycogenolysis involves hydrolysing glycogen into glucose, providing a rapid source of glucose when blood glucose concentrations fall.

Question 9

Describe how adrenaline affects blood glucose concentration.

Answer 9

Adrenaline stimulates glycogenolysis and inhibits insulin secretion, ensuring more glucose is available for respiration during stress or exercise.

Question 10

Describe the roles of the liver and pancreas in blood glucose regulation.

Answer 10

The pancreas (beta cells) secretes insulin and (alpha cells) glucagon to control glucose, while the liver stores glycogen and performs glycogenolysis or glycogenesis as needed.

Question 11

Explain how blood glucose concentration is detected by the body.

Answer 11

In the pancreas beta cells detect high blood glucose then release insulin; alpha cells detect low blood glucose concentration then release glucagon to regulate glucose concentration.

Question 12

Explain the role of beta cells in the pancreas in glucose regulation.

Answer 12

Beta cells secrete insulin in response to high blood glucose concentrations, promoting glucose uptake and storage as glycogen.

Question 13

Explain the role of alpha cells in the pancreas in glucose regulation.

Answer 13

Alpha cells release glucagon when blood glucose concentrations are low, stimulating glycogenolysis and gluconeogenesis in the liver.

Question 14

Explain how type 1 diabetes affects blood glucose control.

Answer 14

Type 1 diabetes occurs when beta cells are destroyed in an autoimmune response, leading to insufficient insulin production and high blood glucose concentrations.

Question 15

Explain how type 2 diabetes affects blood glucose regulation.

Answer 15

Type 2 diabetes involves insulin resistance or insensitivity due to fewer or faulty insulin receptor proteins, thus blood glucose concentrations remain high.

Question 16

Explain the role of the second messenger in the action of adrenaline and glucagon.

Answer 16

Adrenaline and glucagon bind to specific protein receptors on the target cell membrane, activating the enzyme adenylate cyclase. This converts ATP into cyclic AMP (cAMP), the second messenger, which activates protein kinase enzymes. These enzymes trigger glycogenolysis, releasing glucose into the blood.

Question 17

Explain how cyclic AMP (cAMP) amplifies the effects of adrenaline and glucagon.

Answer 17

cAMP acts as a second messenger, activating multiple protein kinase molecules, which in turn activate enzymes responsible for glycogenolysis. This amplification allows a small hormone signal to cause a large glucose release.

Question 18

Explain how the second messenger model ensures specificity in glucose regulation.

Answer 18

Only cells with specific receptors for adrenaline or glucagon produce cAMP. This ensures the second messenger activates glycogenolysis only in appropriate target tissues like the liver.

Question 19

Define negative feedback in the context of blood glucose regulation.

Answer 19

Negative feedback is a homeostatic mechanism where a change in blood glucose concentration is detected and triggers a response that restores levels to the normal range by opposing the initial change.