Control of blood glucose concentration

Question 1

What is the normal concentration of blood glucose?

Answer 1

90mg per 100cm3

Question 2

What monitors the concentration of blood glucose?

Answer 2

Cells in the pancreas

Question 3

When does blood glucose rise?

Answer 3

After eating food containing carbohydrate

Question 4

When does blood glucose fall?

Answer 4

After exercise as more glucose is used in respiration to release energy, when you’re stressed

Question 5

What two hormones are used to control the concentration of blood glucose?

Answer 5

Insulin

Glucagon

Question 6

What is a hormone?

Answer 6

A chemical messenger which travels in blood to their target cells

Question 7

Where is insulin and glucagon secreted from?

Answer 7

Clusters of cells called islets of Langerhans

Question 8

What cells do the Islets of Langerhans contain?

Answer 8

Alpha cells
Beta cells
Delta cells

Question 9

What do beta cells secrete?

Answer 9

Insulin into the blood

Question 10

What do alpha cells secrete?

Answer 10

Glucagon into the blood

Question 11

What are insulin and glucagon examples of?

Answer 11

Effectors

Question 12

What role does insulin play in controlling blood glucose concentrations?

Answer 12

Lowers blood glucose concentration when its too high

Question 13

How does insulin affect cell membranes?

Answer 13

It binds to specific receptors on the cell membranes of muscle and liver cells, increasing the permeability to glucose so more is taken up. Done by increasing the number of channel proteins

Question 14

What enzymes does insulin activate?

Answer 14

Muscle and liver cells that convert glucose into glycogen

Question 15

What is glycogenesis?

Answer 15

The formation of glycogen from glucose

Question 16

What does insulin increase the rate of?

Answer 16

Rate of respiration of glucose

Question 17

What role does glucagon play in controlling blood glucose concentrations?

Answer 17

Raises blood glucose concentration when its too low

Question 18

How does glucagon work?

Answer 18

It binds to specific receptors on the cell membranes of liver cells and activates enzymes that break down glycogen into glucose

Question 19

What process does glucagon activate?

Answer 19

Glycogenolysis

Question 20

What is glycogenolysis?

Answer 20

The formation of glucose from glycogen

Question 21

What is gluconeogenesis?

Answer 21

The formation of glucose from non-carbohydrates such as amino acids and glycerol

Question 22

What is a weakness of a hormonal response to control blood glucose?

Answer 22

It is slower than a nerve impulse response

Question 23

What is a strength of a hormonal response to control blood glucose?

Answer 23

They are not broken down as quickly as neurotransmitters so effects last longer

Question 24

Explain how negative feedback mechanisms respond to a rise in blood glucose concentration?

Answer 24

• When it is detected by the pancreas, the β cells secrete insulin and the α cells stop secreting glucagon
• Insulin binds to receptors on liver and muscle cells
• The liver and muscle cells respond to decrease the blood glucose concentration
• Glycogenesis is activated
• Blood glucose concentration returns to normal

Question 25

Explain how negative feedback mechanisms respond to a fall in blood glucose concentration?

Answer 25

• When it is detected by the pancreas, the α cells secrete glucagon and the β cells stop secreting insulin
• Glucagon binds to receptors on liver cells
• Liver cells respond to increase the blood glucose concentration
• Glycogenolysis is activated
• Blood glucose concentration returns to normal

Question 26

What are glucose transporters?

Answer 26

Channel proteins which allow glucose to be transported across a cell membrane

Question 27

What type of glucose transporter is in skeletal and cardiac muscle cells?

Answer 27

GLUT4

Question 28

What happens to glucose transporters when insulin levels are low?

Answer 28

GLUT4 is stored in vesicles in the cytoplasm but when insulin binds it triggers the movement of GLUT4 to the membrane. Glucose can then be transported into the cell by the protein by facilitated diffusion

Question 29

What is adrenaline?

Answer 29

A hormone secreted from adrenal glands

Question 30

When is adrenaline secreted?

Answer 30

When there’s a low concentration of glucose in your blood

Question 31

What two things does adrenaline do?

Answer 31

Binds to receptors in the cell membranes of liver cells and;

• Activates glycogenolysis (breakdown of glycogen to glucose)
• Inhibits glycogenesis ( the synthesis of glycogen from glucose

Question 32

What does adrenaline get the body ready for?

Answer 32

Making more glucose available for muscles to respire

Question 33

What is the secondary messenger model?

Answer 33

The binding of the hormone to cell receptors activates an enzyme on the inside of the cell membrane, which they produces a chemical known as a second messenger

Question 34

What does a secondary messenger do?

Answer 34

Activates other enzymes in the cell to bring about a response

Question 35

How does adrenaline and glucagon act in terms of the secondary messenger model and activating glycogenolysis? (step by step)

Answer 35

• To activate glycogenolysis, adrenaline and glucagon bind to their receptors and activate an enzyme called adenylate cyclase.
• Activated adenylate cyclase converts ATP into a chemical called cyclic AMP (cAMP) which is a secondary messenger
• cAMP activates an enzyme called protein kinase A
• Protein kinase A activates a chain of reactions which breaks down glycogen into glucose

Question 36

Why are glucagon and adrenaline receptors complimentary in shape to their respective hormones?

Answer 36

They have a specific tertiary structure