Control of blood glucose

Question 1

What factors affect blood glucose concentration?

Answer 1

Food (carbohydrates) and glycogen stores

Question 2

What is glycogenesis?

Answer 2

The production of glycogen from glucose

Question 3

What is glycogenolysis?

Answer 3

The hydrolysis of glycogen to produce glucose

Question 4

What is gluconeogenesis?

Answer 4

The production of glucose from non-carbohydrate organic molecules

Question 5

What releases insulin?

Answer 5

Beta cells

Question 6

Where are beta cells and alpha cells found?

Answer 6

Pancreas

Question 7

What is released when glucose concentration is high?

Answer 7

Insulin is released, and alpha cells stop producing glucagon

Question 8

How is insulin secreted?

Answer 8

• Beta cells have K+ channels open constantly so K+ ions move out
• Less positive inside the cell
• When there is too much glucose, it enters though a transport channel
• Metabolic reactions occur so glucose is converted to ATP which closes the K+ channels so it becomes more positive inside
• This leads to membrane depolarisation
• Therefore, voltage-gated Ca++ channels open and Calcium ions enter the cell.
• This stimulates the exocytosis of insulin from the cell into the bloodstream

Question 9

Where does insulin go via the blood?

Answer 9

Hepatocytes (liver cells)

Question 10

Describe the insulin mechanism

Answer 10

• Attaches to membrane-bound receptor
• Stimulates Adenylyl cyclase, ATP converted to cAMP
• cAMP opens glucose channels (increases membrane permeability to glucose) and converts glucose into non-carbohydrate organic molecules
• Activation of enzymes
• cAMP also stimulates glycogenesis (glucose to glycogen)
• This lowers the concentration of glucose in the blood

Question 11

What is released when there is low blood glucose concentration?

Answer 11

Alpha cells release glucagon and beta cells stop releasing insulin

Question 12

Describe the glucagon mechanism

Answer 12

• Glucagon attaches to a hepatocyte membrane-bound receptor
• Stimulate Adenylyl cyclase which converts ATP to cAMP
• cAMP triggers protein kinase which results in glycogenolysis
• cAMP also triggers gluconeogenesis

Question 13

What is the first messenger model?

Answer 13

The binding of a substance to the cell-surface membrane which triggers intracellular activity

Question 14

What is the second messenger model?

Answer 14

Molecules that initiate activity inside the cell

Question 15

Describe the adrenaline mechanism

Answer 15

• Binds to membrane-bound receptor on liver cell
• Stimulates adenylyl cyclase to convert ATP to cAMP
• Triggers a series of enzyme reaction including protein kinase
• Glycogenolysis
• Concentration of glucose increases

Question 16

What causes type 1 diabetes?

Answer 16

• Mostly genetic factors

- Immune system attacks beta cells so no insulin can be secreted.

Question 17

What causes type 2 diabetes?

Answer 17

• Mostly lifestyle factors

- High blood glucose concentration, insulin eventually has no effect and can’t reduce glucose conc.