Blood glucose concentration

Question 1

Glycogenesis

Answer 1

The synthesis of glycogen from glucose

Question 2

Glycogenolysis

Answer 2

The breakdown of glycogen into glucose

Question 3

Gluconeogenesis

Answer 3

The synthesis of glucose from non-carbohydrates e,g glycerol and amino acids

Question 4

What happens if blood glucose concentration is too high?

Answer 4

Lowers the water potential of the blood so water moves out of the cells and into the blood - can cause cells to shrivel up and die.

Question 5

What happens if blood glucose concentration is too low?

Answer 5

Cells cannot carry out normal functions as there isn’t enough glucose for respiration to provide energy

Question 6

When is insulin secreted?

Answer 6

When the blood glucose concentration is too high!!

Question 7

When is glucagon secreted?

Answer 7

When the blood glucose concentration is too low!!

Question 8

What are the 3 roles of insulin?

Answer 8

attaching to specific receptors on surfaces of target cells
controlling the uptake of glucose by regulating the inclusion of channel proteins in the surface membranes of target cells
Activating enzymes in the conversion of glucose to glycogen (glycogenesis)

Question 9

What is the overall role of insulin?

Answer 9

To lower the blood glucose concentration

Question 10

What are the 3 roles of glucagon?

Answer 10

attaching to receptors on the surface of target cells
activating enzymes involved in the conversion of glycogen to glucose (glycogenolysis)
activating enzymes involved in the conversion of glycerol and amino acids to glycogen (gluconeogenesis)

Question 11

What is the overall role of glucagon?

Answer 11

To raise the blood glucose concentration

Question 12

Describe how insulin lowers the blood glucose concentration?

Answer 12

Binds to specific receptors on the surfaces of muscle and liver cells (hepatocytes)
Increases the permeability to glucose of muscle cell membranes so cells take up more glucose
It increases permeability by increasing the number of channel proteins in cell membranes
Activates enzymes in muscle and liver cells that convert glucose –> glycogen (stored in cells cytoplasm as energy source)
Increases the rate if respiration of glucose, especially in muscle cells.

Question 13

Describe how glucagon rasies the blood glucose concentration?

Answer 13

Binds to specific receptors on cell membranes of liver cells
Activates enzymes that break down glycogen into glucose (glycogenolysis)
Activates enzymes involved in the formation of glucose from amino acids and glycerol (non-carbs) - gluconeogenesis
Lowers the rate of respiration of glucose in cells

Question 14

What detects low and high blood glucose concentration?

Answer 14

The pancreas

Question 15

Where are the alpha and beta cells found in the pancreas?

Answer 15

Islets of Langerhans

Question 16

Which cell secretes insulin?

Answer 16

Beta cells

Question 17

Which cell secretes glucagon?

Answer 17

Alpha cells

Question 18

What are glucose transporters?

Answer 18

They are channel proteins which allow glucose to be transported across a cell membrane.

Question 19

Which glucose transporter do skeletal and cardiac muscle cells contain?

Answer 19

GLUT4

Question 20

What is the state of GLUT4 when insulin levels are low?

Answer 20

Stored in vesicles in the cell cytoplasm

Question 21

What happens to GLUT4 when insulin binds to the specific receptors found on the cell membranes of target cells? e.g. liver or muscle cells

Answer 21

Triggers the movement of GLUT4 towards the membrane. Glucose can then be transported into the cell through the GLUT4 channel protein BY FACILITATED DIFFUSION

Question 22

Where is adrenaline secreted from?

Answer 22

The adrenal glands

Question 23

Why is adrenaline secreted?

Answer 23

When there is a low concentration of glucose in the blood (e.g. stressed/exercising)

Question 24

How does adrenaline increase blood glucose concentration?

Answer 24

Activates glycogenelysis
Inhibits glycogenesis
Activates glucagon secretion
Inhibits insulin secretion
which both = increase in blood glucose concentration

Question 25

Where does adrenaline bind?

Answer 25

To the receptors in the cell membrane of liver cells

Question 26

How does adrenaline get the body ready for ‘action’?

Answer 26

makes more glucose available for muscles to respire

Question 27

What does the second messenger model allow glucagon and adrenaline to do?

Answer 27

When they bind to the specific receptors on the outside of the cell - it allows them to activate glycogenolysis inside the cell.

Question 28

How does the second messenger model work?

Answer 28

The binding of the hormone to the receptors on the outside of the cell activates an enzyme on the inside of the cell membrane which produces a chemical known as a second messenger.
The second messenger activates other enzymes which bring about a response.

Question 29

In order to activate glycogenolysis which enzymes do glucagon and adrenaline activate when they bind to their receptors?

Answer 29

Adenylate cyclase (aka adenylyl cyclase)

Question 30

What does activated adenylate cyclase do?

Answer 30

It converts ATP into a chemical called cAMP (cyclic AMP)

Question 31

What is cAMP?

Answer 31

Cyclic AMP - which is a second messenger

Question 32

What enzymes does cAMP activate?

Answer 32

Protein kinase A

Question 33

What does protein kinase A activate?

Answer 33

A series of chain reactions (a cascade) which causes the breakdown of glycogen into glucose