Biology- Homeostasis Exam Questions

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 marks

1. Changes tertiary structure;
Reject change in tertiary structure of receptor.
2. No longer complementary (to receptor);
Reject 'active site' or reference to enzyme or substrate

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

1. High concentration of glucose in blood/filtrate;
Accept tubule for filtrate.
2. Not all the glucose is (re)absorbed at the proximal convoluted tubule;
Reject no glucose is (re)absorbed.
3. Carrier/co-transport proteins are working at maximum rate OR
Carrier/co-transport proteins/ are saturated;

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

1. (Attaches to receptors on target cells and) activates/stimulates enzymes;
Reject 'produces enzymes'.
2. Glycerol/amino acids/fatty acids into glucose

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 marks

1. (More) insulin binds to receptors;
2. (Stimulates) uptake of glucose by channel/transport proteins
OR
Activates enzymes which convert glucose to glycogen

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

1. Less/no ATP is converted to cyclic AMP/cAMP;
2. Less/no kinase is activated;
3. Less/no glycogen is converted to glucose
OR
Less/no glycogenolysis;

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 marks

1. (Usually)Type II produce insulin;
2. Cells / receptors less sensitive / responsive (to insulin)
3. (Treated / controlled by) diet / exercise;

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

1. Treat with insulin injections
2. Control diet/ sugar intake

cientists 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.
(a) Explain how the normal mice prevented their blood glucose concentration falling when they had not eaten for 48 hours.
3 marks

1. Release of glucagon
2. Leads to formation of glucose in liver cells
3. From non- carbohydrates/ amino acids ( gluconeogenesis)

When insulin binds to receptors on liver cells, it leads to the formation of glycogen from glucose. This lowers the concentration of glucose in liver cells. Explain how the formation of glycogen in liver cells leads to a lowering of blood glucose concentration.
2 marks

1. Formation of glycogen maintains glucose concentration/ diffusion gradient
2. Glucose enters cell by facilitated diffusion

Adrenaline binds to receptors in the plasma membranes of liver cells. Explain how this causes the blood glucose concentration to increase.
2 marks

1. ADENYLATE CYCLASE activated/ cAMP produced
2. Activates enzymes involved into glycogenolysis

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 marks

1. Glycogen to glucose/ glycogenolysis activated by enzymes

2. Blood glucose concentration increases

Alport syndrome (AS) is an inherited disorder that affects kidney glomeruli of both men and women. Affected individuals have proteinuria (high quantities of protein in their urine).
(a) Suggest how AS could cause proteinuria.
2 marks

1. Affects/damages basement membrane
OR
More protein channels/carriers in basement membrane;
2. Proteins can pass into the (glomerular) filtrate/tubule;

Describe how ultrafiltration occurs in a glomerulus.
3 marks

1.High blood/hydrostatic pressure;
2. Two named small substances pass out eg water, glucose, ions, urea;
3. (Through small) gaps/pores/fenestrations in (capillary) endothelium;
Accept epithelium for endothelium
4. (And) through (capillary) basement membrane;

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.
3 marks

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

.Osmoreceptors are specialised cells that respond to changes in the water potential of the blood.
(a) Give the location of osmoreceptors in the body of a mammal.
1 mark

Hypothalamus

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

1. Water potential will decrease
2. Water moves from osmoreceptors into blood by osmosis

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.
4 marks

1. Permeability of membrane to water is increased
2. More water absorbed from collecting duct
3. Small volume of urine
4. Urine becomes concentrated

In a mammal, urea is removed from the blood by the kidneys and concentrated in the filtrate.
(a) Describe how urea is removed from the blood.
2 marks

1. Hydrostatic pressure
2. Causes ULTRAFILTRATION at Bowman's capsule
3. Through basement membrane
2 max

Explain how urea is concentrated in the filtrate.
3 marks

1. Reabsorption of water by osmosis
2. at the PCT
3. at the collecting duct/ DCT
4. Active transport of ions

Describe how ultrafiltration produces glomerular filtrate
5 marks

1. Blood pressure/ hydrostatic pressure
2. Small molecules
3. Pass through basement membrane
4. Protein too large to pass through/ stay behind
5. Prescence of pores in the capillaries/ presence of podocyte

Some people who have diabetes do not secrete insulin. Explain how a lack of insulin affects reabsorption of glucose in the kidneys of a person who does not secrete insulin.
4 marks

1. High concentration of glucose in the blood
2. High concentration in tubule
3. Reabsorbed by facilitated diffusion/ active transport
4. Requires proteins
5. Not all glucose reabsorbed
6. As proteins are working at a maximum rate

Some desert mammals have long loops of Henle and secrete large amounts of antidiuretic hormone (ADH). Explain how these two features are adaptations to living in desert conditions.
6 marks

For general:
1. More water from filtrate reabsorbed
2. By osmosis
3. From collecting duct
4. Due to longer Loop of Henle

Loop of Henle:
1. Sodium/ Chloride ions absorbed from filtrate in ascending limb
2. Gradient established in medulla

ADH:
1. Acts on collecting duct
2. Makes cells more permeable

TO GAIN FULL MARKS YOU NEED ONE SPECIFIC POINT ABOUT LoH and ADH AS WELL AS GENERAL POINTS FOR BOTH

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 person. Explain why.
3 marks

In diabetic person:
1. Lack of insulin
2. REDUCED uptake of glucose by cells
3. REDUCED conversion of glucose to glycogen

The urine of a non-diabetic person does not contain glucose. Explain why
2 marks

1. Leaves blood at the kidney
2. Taken back into blood
3. Reabsorbed in FIRST CONVULUTED TUBE
2 max ( must mention kidney/ named part)

A high blood glucose concentration could cause glucose to be present in the urine of a diabetic person. Suggest how.
2 marks

1. Large amount of glucose in FILTRATE
2. Cannot all be reabsorbed

A test for glucose in urine uses immobilised enzymes on a plastic test strip. One of these enzymes is glucose oxidase. Explain why the test strip detects glucose and no other substance.
2 marks

1. Enzyme has specific SHAPE to ACTIVE SITE/ active site has specific tertiary structure
2. Only glucose fits/ has complementary structure/ can from ES complex

If the glomerular filtrate of a diabetic person contains a high concentration of glucose, he produces a larger volume of urine. Explain why.
3 marks

1. Glucose in FILTRATE lowers water potential
2. LOWER water potential gradient
3. Less water reabsorbed by osmosis

In some forms of kidney disease, proteins from the blood plasma are found in the urine. Which part of the nephron would have been damaged by the disease to cause proteins from blood plasma to be present in the urine? Explain your answer.
3 marks

1. Glomerulus/ Bowman's capsule
2. Basement membrane
3. Proteins are large/ cannot normally pass through

The kangaroo rat is a small desert mammal. It takes in very little water in its food and it rarely drinks. Its core body temperature is 38 °C. The kangaroo rat takes in some water by feeding and drinking. Describe another method by which the kangaroo rat could obtain water.
2 marks

From aerobic respiration = 2 marks

Where does ADH get released from?

posterior pituitary gland