I/E: Control of Blood Glucose Concentration

Question 1

What is blood glucose monitored by?

Answer 1

Cells in the pancreas.

Question 2

What is the normal concentration of glucose in the blood?

Answer 2

Around 90mg per 100cm³

Question 3

What happens to blood glucose after exercise?

Answer 3

It falls - as more glucose is used in respiration to release energy.

Question 4

What happens to blood glucose concentration after eating carbohydrates?

Answer 4

It rises

Question 5

What two hormones control blood glucose concentration?

Answer 5

Insulin and glucagon

Question 6

What secretes insulin into the blood?

What secretes glucagon into the blood?

Answer 6

Insulin = beta cells in the islets of Langerhans

Glucagon = alpha cells in the islets of Langerhans

Question 7

What is the role of insulin in controlling blood glucose?

Answer 7

It lowers blood glucose concentration when it is too high.

Question 8

How does insulin lower blood glucose concentration?

Answer 8

1. Insulin binds to receptors on cell membranes of liver cells and muscle cells.
2. Increases the permeability of muscle-cell membranes to glucose.
3. Cells take up glucose by increasing the number of channel proteins in the cell membranes.
4. Insulin also activates enzymes in liver and muscle cells that convert glucose to glycogen - glycogenesis.
5. Insulin also increases the rate of respiration of glucose, esp. in muscle cells.

Question 9

What is the role of glucagon in controlling blood glucose concentration?

Answer 9

It raises blood glucose concentration when it’s too low.

Question 10

How does glucagon raise blood glucose concentration?

Answer 10

1. Glucagon binds to receptors on cell membranes of liver cells.
2. Activates enzymes that break down glycogen into glucose - glycogenolysis.
3. Glucagon also activates enzymes involverd in the formation of glucose from glycerol and amino acids -gluconeogenesis.
4. Also decreases rate of respiration of glucose in cells.

Question 11

Glycogenesis

Answer 11

The process of forming glycogen from glucose.

Question 12

Glycogenolysis

Answer 12

The process of breaking down glycogen.

Question 13

Gluconeogenesis

Answer 13

The process of forming glucose from non-carbohydrates.

Question 14

What type of feedback mechanisms keep blood glucose normal?

Answer 14

Negative feedback

Question 15

Describe the negative feedback mechanism when blood glucose is too high:

Answer 15

• Pancreas detects change in blood glucose.
• B cells secrete insulin, a cells stop secreting glucagon.
• Insulin binds to receptors on liver and muscle cells.
  
  • Cells take up more glucose.
  • Glycogenesis is activated.
  • Cells respire more glucose.
• Less glucose in the blood - normal concentration.

Question 16

Describe the negative feedback mechanisms when blood glucose concentration is too low:

Answer 16

• Pancreas detects change.
• a cells secrete glucagon, B cells stop secreting insulin.
• Glucagon binds to receptors on liver cells.
  
  • Glycogenolysis is activated.
  • Gluconeogenesis is activated.
  • Cells respire less glucose.
• Cells release glucose into the blood - normal levels return.

Question 17

GLUT4

Answer 17

A channel protein that transports glucose in skeletal and cardiac muscle cells.

Question 18

Where is GLUT4 stored when insulin levels are low?

Answer 18

In vesicles in the cytoplasm of cells.

Question 19

What happens to GLUT4 when insulin binds to receptors on the cell-surface membrane?

Answer 19

It’s movement is triggered to the membrane.

GLUT4 can then be transported into the cell through the GLUT4 protein, by facilitated diffusion.

Question 20

When is adrenaline secreted?

Answer 20

When blood glucose concentration is low, when you’re stressed and when you’re exercising.

Question 21

What is the role of adrenaline in controlling blood glucose concentration?

Answer 21

Binds to receptors in the cell membrane of liver cells.

• Activates glycogenolysis.
• Inhibits glycogenesis.
• Activates glucagon secretion and inhibits insulin secretion = increasing blood glucose.

Question 22

How does adrenaline get the body ready for action?

Answer 22

Makes more glucose available for muscles to respire.

Question 23

What is special about adrenaline and glucagon?

Answer 23

Act via a second messenger - can activate glycogenolysis inside a cell even though they bind to receptors outside the cell.

Question 24

Describe the second messenger model:

Answer 24

1. Glucagon/insulin binds to receptors and activates adenylate cyclase.
2. Converts ATP into a chemical signal called a ‘second messenger’ = cyclic AMP.
3. cAMP activates enzyme protein kinase A.
4. Protein kinase A activates a cascade that breaks down glycogen into glucose - glycogenolysis.

Question 25

Name a condition that occurs when blood glucose concentration is not controlled:

Answer 25

Diabetes mellitus

Question 26

What is the cause of Type 1 diabetes?

Answer 26

Immune system attacks B cells in islets of Langerhans so they don't produce insulin. ## Footnote *Believed that a genetic predisposition or development of a viral infection might trigger this.*

Question 27

In Type 1 diabetes, what happens after eating?

Answer 27

Blood glucose levels rise and stay high - hyperglycaemia. *Kidneys can't reabsorb all the glucose and so some is excreted in urine.*

Question 28

How is Type 1 diabetes treated?

Answer 28

* Insulin therapy - regular insulin injections/insulin pump. * Eating regularly and controlling simple carbonhydrate intake to avoid sudden rise in glucose.

Question 29

What are the risk factors for Type 2 diabetes?

Answer 29

* Obesity * Family history * Lack of exercise * Age * Poor diet.

Question 30

What is wrong with B cells in Type 2 diabetes?

Answer 30

B cells don't produce enough insulin or when the body cells don't respond properly to insulin because the insulin receptors on their membranes don't work.

Question 31

How is Type 2 diabetes treated?

Answer 31

* Eating a balanaced diet. * Weight loss. * Regular exercise. * Glucose-lowering medication can be taken. * Insulin injections may be needed.

Question 32

How have health advisors responded to the increase in Type 2 diabetes?

Answer 32

* NHS campaigns like 'Change4Life' - educate people on healthier lifestyle choices. * Challenged food industry to reduce the advertising of junk food especially to children, to improve the nutritional value of products and to use clearer labelling on products.

Question 33

How have food companies responded to criticism?

Answer 33

* Using sugar alternatives to sweeten food/drinks. * Reducing sugar, fat and salt content of products.

Question 34

What is the normal concentration of glucose in urine ?

Answer 34

Between 0 and 0.8 mM

Question 35

How is quantitative Benedict's reagent different to normal Benedic't reagent?

Answer 35

When heated with glucose, the initial blue colour is lost but a brick-red precipitate is not produced.

Question 36

What is a colorimeter used for?

Answer 36

To measure the light absorbance of the solution after the quantitative Benedict's test has been carried out.

Question 37

Describe the absorbance of a solution with a high concentration of glucose:

Answer 37

The higher the concentration of glucose, the more blue colour will be lost, decreasing the absorbance of the solution.

Question 38

Describe how you would make a calibration curve and use it to test a urine sample:

Answer 38

1. Perform a quantitative Benedict's test on each solution and a negative control of pure water. 2. (Add to a water bath that's at boiling point) 3. Use a colorimeter (with a red filter) to measure the absorbance of the Benedict's solution remaining in each tube. 4. Use results to make the calibration curve showing absorbance against glucose concentration. 5. Test the urine sample, in the same way as the known concentrations, and use the claibration curve to find the concentration of glucose in the sample.