Exam questions · Biology
The Kidneys
- 24 exam questions
- 70 marks
- 36 quick checks
The Urinary System and Urea
Just this lesson-
1 State [1 mark]
State the organ in which urea is made.
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Model answer
The liver.
Mark scheme
- Liver — 1 mark
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2 Name [2 marks]
Name the tube that carries urine from the kidney to the bladder, and the tube that carries urine out of the body.
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Model answer
The ureter carries urine from the kidney to the bladder, and the urethra carries it out of the body.
Mark scheme
- Ureter — 1 mark
- Urethra — 1 mark
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3 Describe [3 marks]
Describe how urea is made in the body.
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Model answer
Excess amino acids that are not needed to make proteins are broken down in the liver. The nitrogen in them is converted into urea. The urea is released into the blood.
Mark scheme
- Excess amino acids are broken down — 1 mark
- In the liver — 1 mark
- Urea is released into the blood — 1 mark
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4 Explain [2 marks]
Explain why urea must be removed from the blood.
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Model answer
Urea is a toxic waste product. If it builds up in the blood, it can damage the cells and the body.
Mark scheme
- Toxic — 1 mark
- Builds up and damages cells — 1 mark
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5 Explain [3 marks]
Explain why the blood in the renal vein has less urea than the blood in the renal artery.
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Model answer
The kidney filters the blood. The urea is removed from the blood in the kidney, and leaves the body in the urine. So the blood that leaves the kidney in the renal vein has little urea.
Mark scheme
- The kidney filters the blood — 1 mark
- Urea removed from the blood — 1 mark
- Leaves in the urine — 1 mark
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6 Evaluate [6 marks]
Describe the path of urea from the cells of the body to the outside of the body, and explain why it is important that urea is removed.
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Model answer
Excess amino acids are broken down in the liver, which makes ammonia and then urea. The urea is released into the blood plasma, and carried to the kidneys in the renal artery. The kidneys filter the urea out of the blood, and it is part of the urine, which is carried down the ureters to the bladder, where it is stored. The urine leaves the body through the urethra. The blood that leaves the kidney in the renal vein has little urea. It is important to remove urea because it is toxic, and it would damage the cells and the body if it built up in the blood.
Mark scheme
- Amino acids broken down in the liver — 1 mark
- Urea released into the blood — 1 mark
- Carried to the kidney — 1 mark
- Filtered out, in urine — 1 mark
- Ureter, bladder, urethra — 1 mark
- Toxic if it builds up — 1 mark
Quick check
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1
Where is urea made?
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C: In the liver
In the liver, from excess amino acids.
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2
What is urea made from?
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B: Excess amino acids
Excess amino acids.
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3
Which organ stores urine?
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D: The bladder
The bladder.
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4
What does the ureter do?
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A: Carries urine from the kidney to the bladder
It carries urine from the kidney to the bladder.
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5
What does the urethra do?
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B: Carries urine out of the body
It carries urine from the bladder out of the body.
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6
Which vessel carries blood into the kidney?
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C: The renal artery
The renal artery.
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7
Why must urea be removed from the body?
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A: It is toxic
It is toxic.
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8
Which blood vessel has the lowest concentration of urea?
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D: The renal vein
The renal vein, because the kidney has filtered the blood.
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9
Which of these is NOT part of the urinary system?
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B: The pancreas
The pancreas is not part of the urinary system.
The Nephron and the Formation of Urine
Just this lesson-
1 State [1 mark]
State where the blood is filtered in a nephron.
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Model answer
In the glomerulus and Bowman's capsule.
Mark scheme
- Glomerulus and capsule — 1 mark
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2 Name [2 marks]
Name two substances that are found in the blood but not in the filtrate.
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Model answer
Blood cells and proteins.
Mark scheme
- Blood cells — 1 mark
- Proteins — 1 mark
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3 Explain [3 marks]
Explain why blood cells are not found in the filtrate.
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Model answer
Blood cells are too big to pass through the walls of the capillaries in the glomerulus. Only small molecules are forced out by the high pressure.
Mark scheme
- Too big — 1 mark
- To pass through the capillary walls — 1 mark
- Only small molecules are filtered — 1 mark
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4 Explain [3 marks]
Explain why there is no glucose in the urine of a healthy person.
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Model answer
Glucose is filtered into the nephron, because it is a small molecule. All of it is reabsorbed into the blood from the tubule, by active transport, so there is none in the urine.
Mark scheme
- Glucose is filtered — 1 mark
- All of it is reabsorbed — 1 mark
- By active transport — 1 mark
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5 Calculate [2 marks]
The concentration of urea in the plasma is 0.03 g per 100 cm³ and in the urine is 1.80 g per 100 cm³. Calculate how many times more concentrated the urea is in the urine.
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Model answer
1.80 divided by 0.03 is 60 times.
Mark scheme
- 1.80 divided by 0.03 — 1 mark
- 60 times — 1 mark
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6 Evaluate [6 marks]
Describe how the kidney forms urine from blood, and explain how the structure of the nephron helps this.
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Model answer
Blood flows into the glomerulus, where the pressure is high, because the vessel that leaves is narrower. The high pressure forces small molecules, such as water, glucose, urea and ions, out through the thin walls of the capillaries into Bowman's capsule, but blood cells and proteins are too big, so they stay in the blood. This is filtration, and it is not selective. In the first part of the tubule, all of the glucose is reabsorbed into the blood by active transport, which needs energy, so the cells have many mitochondria. Water is reabsorbed by osmosis, in the loop of Henle and the collecting duct. The urea is not reabsorbed, so it leaves in the urine with the excess water and excess ions.
Mark scheme
- High pressure forces small molecules out — 1 mark
- Cells and proteins stay in the blood — 1 mark
- All glucose reabsorbed — 1 mark
- By active transport, using energy — 1 mark
- Water reabsorbed by osmosis — 1 mark
- Urea leaves in the urine — 1 mark
Quick check
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1
Where does filtration take place?
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B: In the glomerulus and Bowman's capsule
In the glomerulus and Bowman's capsule.
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2
Which of these is NOT filtered out of the blood into the capsule?
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D: Blood cells
Blood cells are too large.
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3
How is glucose reabsorbed?
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C: By active transport
By active transport.
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4
How is water reabsorbed?
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A: By osmosis
By osmosis.
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5
What is the liquid in Bowman's capsule?
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B: The filtrate
The filtrate.
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6
Why does the proximal tubule have many mitochondria?
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D: To supply energy for active transport
To supply energy for active transport.
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7
What is in the urine of a healthy person?
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A: Urea, excess ions and excess water
Urea, excess ions and excess water.
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8
Why does the glomerulus have a high pressure?
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C: The vessel leaving is narrower than the one entering
The vessel that leaves is narrower than the vessel that enters.
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9
Why is the urea more concentrated in urine than in the plasma?
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B: Water is reabsorbed but urea is not
Water is reabsorbed but urea is not.
ADH and Water Balance (Higher tier)
Just this lesson-
1 State [1 mark]
State the name of the gland that releases ADH.
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Model answer
The pituitary gland.
Mark scheme
- Pituitary gland — 1 mark
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2 Describe [2 marks]
Describe the effect of ADH on the collecting duct.
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Model answer
ADH makes the walls of the collecting duct more permeable to water, so more water is reabsorbed into the blood.
Mark scheme
- More permeable to water — 1 mark
- More water reabsorbed — 1 mark
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3 Explain [3 marks]
Explain why a person who has not had a drink for a long time produces a small volume of dark urine.
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Model answer
The water content of the blood falls, so more ADH is released by the pituitary gland. ADH makes the collecting ducts more permeable, so more water is reabsorbed into the blood. So the urine has a small volume, and it is concentrated and dark.
Mark scheme
- More ADH released — 1 mark
- Collecting duct more permeable, more water reabsorbed — 1 mark
- Small volume of concentrated urine — 1 mark
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4 Explain [3 marks]
Explain what happens to the release of ADH after a person drinks a large amount of water.
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Model answer
The water content of the blood rises, and the hypothalamus detects it. The pituitary gland releases less ADH, so the collecting duct is less permeable, less water is reabsorbed, and a large volume of dilute urine is produced.
Mark scheme
- Water content rises, detected — 1 mark
- Less ADH released — 1 mark
- Less water reabsorbed, dilute urine — 1 mark
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5 Explain [3 marks]
Explain why the control of the water content of the blood is an example of negative feedback.
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Model answer
A fall in the water content causes the release of ADH, which causes more water to be reabsorbed, so the water content rises back to normal. When it is normal, less ADH is released. The response reverses the change.
Mark scheme
- Change causes ADH release — 1 mark
- Response reverses the change — 1 mark
- Less ADH when normal — 1 mark
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6 Evaluate [6 marks]
A person has a condition in which the pituitary gland does not release ADH. Predict the effects on the person's urine and explain them, and suggest how the person could be treated.
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Model answer
Without ADH, the walls of the collecting duct stay impermeable to water, so very little water is reabsorbed by osmosis. The person produces a very large volume of dilute urine, and loses a lot of water from the body. The blood becomes more concentrated, so the person is very thirsty, and could become dehydrated. The person could be treated by taking a drug that acts like ADH, for example as a nasal spray, so that the collecting duct is more permeable, and more water is reabsorbed. The person also needs to drink enough water.
Mark scheme
- Collecting duct impermeable without ADH — 1 mark
- Little water reabsorbed by osmosis — 1 mark
- Large volume of dilute urine — 1 mark
- Dehydration or thirst — 1 mark
- Treat with ADH or a similar drug — 1 mark
- Drink enough water — 1 mark
Quick check
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1
Which gland releases ADH?
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C: The pituitary
The pituitary gland.
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2
What does ADH do?
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A: Makes the collecting duct more permeable to water
It makes the collecting duct more permeable to water.
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3
What happens to the urine when there is a lot of ADH?
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D: A small volume of concentrated urine
It is a small volume of concentrated urine.
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4
When is a lot of ADH released?
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B: When the water content of the blood is too low
When the water content of the blood is too low.
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5
How does water move out of the collecting duct?
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A: By osmosis
By osmosis.
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6
After a large drink, what happens to ADH release?
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C: Less is released
Less ADH is released.
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7
What part of the brain detects the water content of the blood?
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D: The hypothalamus
The hypothalamus.
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8
Why is urine dark on a hot day?
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B: It is concentrated, because more water is reabsorbed
It is concentrated, because more water is reabsorbed.
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9
What type of control is the control of water content?
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A: Negative feedback
Negative feedback.
Kidney Failure, Dialysis and Transplants
Just this lesson-
1 State [1 mark]
State what is meant by kidney failure.
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Model answer
The kidneys no longer filter the blood properly.
Mark scheme
- Kidneys do not filter the blood — 1 mark
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2 Name [2 marks]
Name two substances that build up in the blood when the kidneys fail.
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Model answer
Urea and excess ions.
Mark scheme
- Urea — 1 mark
- Excess ions, or excess water — 1 mark
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3 Describe [3 marks]
Describe how a dialysis machine removes urea from the blood of a patient.
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Model answer
The blood flows along tubes with partially permeable walls, which are surrounded by dialysis fluid. The dialysis fluid has no urea, so the urea diffuses from the blood, through the membrane, into the fluid. The cleaned blood returns to the patient.
Mark scheme
- Blood flows next to a partially permeable membrane — 1 mark
- Urea diffuses into the dialysis fluid — 1 mark
- Cleaned blood returns to the patient — 1 mark
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4 Explain [3 marks]
Explain why the dialysis fluid is changed during a treatment.
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Model answer
Urea diffuses from the blood into the dialysis fluid, and the concentration of urea in the fluid rises. If the fluid was not changed, the concentration gradient would fall, and the urea would stop moving. New fluid keeps the gradient steep.
Mark scheme
- Urea builds up in the fluid — 1 mark
- Gradient falls without new fluid — 1 mark
- New fluid keeps the gradient steep — 1 mark
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5 Explain [3 marks]
Explain why a patient who has had a kidney transplant has to take drugs for the rest of their life.
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Model answer
The immune system of the patient recognises the antigens on the donor kidney as foreign, and attacks it, which is rejection. The drugs suppress the immune system, so the new kidney is not rejected.
Mark scheme
- Antigens on the donor kidney are foreign — 1 mark
- Immune system attacks, which is rejection — 1 mark
- Drugs suppress the immune system — 1 mark
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6 Evaluate [6 marks]
A patient with kidney failure is offered either regular dialysis or a kidney transplant. Evaluate the two treatments.
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Model answer
Dialysis can be started at once, and it does not need a donor, so it keeps the patient alive while waiting for a kidney. But it takes three to four hours, about three times a week, it restricts the diet, and it is very expensive over many years, and it does not cure the problem. A transplant gives the patient a working kidney, so the patient is free of the machine, can have a more normal diet and life, and it is cheaper in the long run. However, there are too few donors, so the patient may wait a long time. There is a risk of rejection, so the patient has to take immunosuppressant drugs for life, which increases the risk of infection, and the operation is major. A transplant is generally better if a match can be found, but dialysis is needed while waiting.
Mark scheme
- Dialysis available at once — 1 mark
- Dialysis disadvantages: time, diet, expense — 1 mark
- Transplant gives a normal life — 1 mark
- Transplant cheaper in the long run — 1 mark
- Shortage of donors and rejection — 1 mark
- Balanced conclusion — 1 mark
Quick check
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1
What builds up in the blood in kidney failure?
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B: Urea and excess ions
Urea and excess ions.
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2
What does dialysis fluid contain?
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C: Glucose and ions at healthy concentrations, but no urea
Glucose and ions at healthy concentrations, but no urea.
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3
How does urea leave the blood in dialysis?
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A: By diffusion through a partially permeable membrane
By diffusion through a partially permeable membrane.
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4
Why does the dialysis fluid contain glucose?
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D: So that glucose does not diffuse out of the blood
So that glucose does not diffuse out of the blood.
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5
What is rejection?
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B: The immune system attacks the donor organ
The immune system attacks the donor organ.
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6
Why do transplant patients take immunosuppressant drugs?
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C: To stop rejection of the new kidney
To stop rejection of the new kidney.
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7
How often is dialysis usually needed?
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A: About three times a week
About three times a week.
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8
Which is an advantage of a transplant over dialysis?
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D: The patient can have a more normal life
The patient can have a more normal life.
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9
Which is a disadvantage of kidney transplants?
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B: There are too few donors
There are too few donors.