3.6.4.2 - CONTROL OF BLOOD GLUCOSE CONCENTRATION

Question 1

neonatal diabetes is a disease that affects newly born children the disease is caused by a change in the amino acid sequence of insulin.

this change prevents insulin binding to its receptor.

explain why this change prevents insulin binding to its receptor (2)

Answer 1

1. changes tertiary structure
2. no longer complementary to the receptor

Question 2

describe the role of glucagon in gluconeogenesis (2)

Answer 2

1. attaches to receptors on target cells and activates/stimulates enzymes
2. to convert glycerol/amino acids/fatty acids into glucose

Question 3

metformin is a drug commonly used to treat type II diabetes. metformin’s ability to lower the blood glucose concentration involves a number of mechanisms including:

• increasing a cell’s sensitivity to insulin
• inhibiting adenylate cyclase

explain how increasing a cell’s sensitivity to insulin will lower the blood glucose concentration (2)

Answer 3

1. more insulin binds to reeptors
2. stimulates uptake of glucose by transport proteins OR activates enzymes which convert glucose to glycogen (glycogenesis)

Question 4

metformin is a drug commonly used to treat type II diabetes. metformin’s ability to lower the blood glucose concentration involves a number of mechanisms including:

• increasing a cell’s sensitivity to insulin
• inhibiting adenylate cyclase

explain how inhibiting adenylate cyclase may help to lower blood glucose concentration (3)

Answer 4

1. less/no ATP converted to cAMP
2. less/no kinases activates
3. less/no glycogenolysis

Question 5

each year, a few people with type I diabetes are given a pancreas transplant. pancreas transplants are not used to treat people with type II diabetes.

give two reasons why pancreas transplants are not used for the treatment of type II diabetes (2)

Answer 5

1. type 2 produce insulin
2. cells less responsive to insulin OR faulty insulin receptors
3. can be treated and controlled by diet/exercise

Question 6

give two ways in which people with type 1 diabetes control their blood glucose concentration (2)

Answer 6

1. treat with insulin injections
2. control diet/sugar intake

Question 7

scientists investigated the control of blood glucose concentration in mice. they kept a group of normal mice without food for 48 hours. after 48 hours, the blood glucose concentrations of the mice were the same as at the start of the experiment.

explain how the normal mice prevented their blood glucose concentration falling when they had not eaten for 48 hours (3)

Answer 7

1. release of glucagon
2. leads to formation of glucose in liver cells
3. from non-carbohydrates/amino acids/fatty acids

Question 8

give two reasons why it was important that the mice were given the same food each day (2)

Answer 8

1. food is a factor affecting blood glucose
2. to keep starch intake the same

Question 9

the scientists’ hypothesis was that adding the inhibitor of amylase to the food would lead to a lower blood glucose concentration.

use your knowledge of digestion to suggest how the addition of the inhibitor could lead to a lower blood glucose concentration (2)

Answer 9

1. fewer enzyme substrate complexes formed
2. with inhibitor less starch digested to maltose
3. so less glucose from maltose
4. so less absorption of glucose from the gut

Question 10

when insulin binds to receptors on liver cells, it lead to the formation of glycogen from glucose. this lowers the concentration of glucose in the liver cells.

explain how the formation of glycogen in liver cells leads to a lowering of blood glucose concentration (2)

Answer 10

1. formation of glycogen leads to glucose concentration in liver to fall below that in the blood plasma which creates a glucose concentration gradient
2. glucose enters cell/leaves blood by facilitated diffusion via carrier protein

Question 11

adrenaline binds to receptors in the plasma membranes of liver cells.

explain how this causes the blood glucose concentration to increase (2)

Answer 11

1. adenylate cyclase activated/cAMP produced
2. which activates enzymes in the cell so glycogenolysis/gluconeogenesis occurs

Question 12

the rats were not fed for 6 hours before their blood glucose concentration was measured.

explain why (1)

Answer 12

1. glucose/sugar in the food would affect the results
2. food would affect blood glucose levels
3. allows time for blood glucose levels to return to normal

Question 13

diabetic people who do not control their blood glucose concentration may become unconscious and go into a coma. a doctor may inject a diabetic person who is in a coma with glucagon.

explain how the glucagon would affect the person’s blood glucose concentration (2)

Answer 13

1. glycogenolysis by activating enzymes
2. gluconeogenesis

Question 14

a diabetic person and a non-diabetic person each ate the same amount of glucose.

one hour later, the glucose concentration in the blood of the diabetic person was higher than that of the non-diabetic.

explain why (3)

Answer 14

in diabetic perosn:
1. lack of insulin
2. reduced uptake of glucose by liver cells
3. reduced conversion of glucose to glycogen