homeostasis questions (PMT)

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.

Answer 1

Changes tertiary structure;

No longer complementary (to receptor)

Question 2

A decrease in the activity of PI3K can cause type II diabetes.
Use the figure above to explain why.

Answer 2

Less/no AKT activated;
Fewer/no vesicles move to membrane
Less/no glucose diffuses into cell (so high blood glucose)

Question 3

Using your knowledge of the kidney, explain why glucose is found in the urine of a person with untreated diabetes.

Answer 3

High concentration of glucose in blood/filtrate;

Not all the glucose is (re)absorbed at the proximal convoluted tubule;

Carrier/co-transport proteins are working at maximum rate

Question 4

Describe the role of glucagon in gluconeogenesis.
Do not include in your answer details on the second messenger model of glucagon action.

Answer 4

(Attaches to receptors on target cells and) activates/stimulates enzymes;

Glycerol/amino acids/fatty acids into glucose;

Question 5

Explain how increasing a cell’s sensitivity to insulin will lower the blood glucose concentration.

Answer 5

(More) insulin binds to receptors;
(Stimulates) uptake of glucose by channel/transport proteins

Question 6

Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration.

Answer 6

Less/no ATP is converted to cyclic AMP/cAMP;
Less/no kinase is activated;
Less/no glycogen is converted to glucose

Question 7

Give two reasons why pancreas transplants are not used for the treatment of type II diabetes.

Answer 7

(Usually)Type II produce insulin;
Cells / receptors less sensitive / responsive (to insulin)

Question 8

Give two ways in which people with type 1 diabetes control their blood glucose concentration.

Answer 8

treat with insulin
(Control) diet/control sugar intake

Question 9

Diabetes can damage the nervous system. The response of the rats with diabetes is different from the response of the healthy rats. Use your knowledge of the control of heart rate by the nervous system to suggest an explanation for these results.

Answer 9

1- damage to autonomic nervous system in diabetic rats
2. (Could be) pressure receptors/baroreceptors
(in arteries/aorta/carotid body) don’t work as well;
3. Damage to medulla
4. (When pressure drops damage to)
sympathetic system, so doesn’t speed up (enough);

Question 10

Describe how ultrafiltration occurs in a glomerulus.

Answer 10

1. High blood/hydrostatic pressure
2. water and glucose pass out
3. (Through small) gaps/pores/fenestrations in (capillary) endothelium

Question 11

Furosemide is sometimes used to treat high blood pressure.
Suggest how furosemide would cause a decrease in blood pressure.

Answer 11

lower volume of blood

Question 12

Furosemide inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons.
Explain how furosemide causes an increase in the volume of urine produced.

Answer 12

1. Water potential of filtrate/tubule decreased
2. Less water (reabsorbed) by osmosis (from filtrate/tubule)
3. Collecting duct (is where osmosis occurs)

Question 13

Give the location of osmoreceptors in the body of a mammal.

Answer 13

hypothalamus

Question 14

When a person is dehydrated, the cell volume of an osmoreceptor decreases.
Explain why.

Answer 14

1. water potential of blood will decrease
2. Water moves from osmoreceptor into blood by osmosis.

Question 15

Stimulation of osmoreceptors can lead to secretion of the hormone ADH. Describe and explain how the secretion of ADH affects urine produced by the kidneys.

Answer 15

1. permeability of membranes
2. more water absorbed from the collecting duct
3. Smaller volume of urine;
4. Urine becomes more concentrated.

Question 16

Creatinine is a breakdown product of creatine found in muscle tissues. Apart from age and gender, give two factors that could affect the concentration of creatinine in the blood.

Answer 16

muscle/body mass
ethnicity
exercise.

Question 17

The secretion of osteocalcin (in an inactive form) by osteoblasts is controlled by positive feedback.
Use information from the diagram to explain why this is positive feedback.

Answer 17

1. Osteocalcin causes more (release of) insulin;
2. (More) insulin causes more (inactive) osteocalcin (release)

Question 18

The acidic pH conditions created by osteoclasts cause the inactive form of the protein osteocalcin to change into the active form of osteocalcin.
Suggest how.

Answer 18

1. (Change in pH) changes / breaks ionic / hydrogen bonds;
2. Changes tertiary structure

Question 19

Binding of insulin leads to an increase in the rate of respiration in cells such as osteoblasts.
Explain how.

Answer 19

1.(Insulin) leads to more transport proteins / channel (proteins) / carrier (proteins) for glucose
2. More glucose (for respiration / glycolysis) enters cell

Question 20

(a)Use information in the diagram to suggest how the binding of interferon gamma to its receptor protein leads to the production of phosphorylated STAT1.

Answer 20

1. Binding (of interferon gamma) changes shape/tertiary structure of
   receptor (protein);
2. This activates/switches on the enzyme;
3. Use of ATP (to phosphorylate STAT1)

Question 21

The regulation of the formation of helper T cells by interferon gamma is an example of positive feedback.
Explain why it is an example of positive feedback.

Answer 21

1.causes more helper t-cells to form
2.(So) more interferon (gamma) production - by helper T cells