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Exam questions · Biology · Hormonal Coordination in Humans

Kidney Failure, Dialysis and Transplants

  • 7 exam questions
  • 22 marks
  • 8 quick checks
  1. 1 State [2 marks]

    State two treatments for kidney failure.

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    Model answer

    Dialysis (using a machine) and a kidney transplant.

    Mark scheme

    • Dialysis — 1 mark
    • Kidney transplant — 1 mark
  2. 2 Name [3 marks]

    Figure 1 shows a dialysis machine. Name the parts shown at A, B and C.

    A dialysis machine with three parts marked A, B and C.
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    Model answer

    A is the partially permeable membrane. B is the dialysis fluid. C is the blood.

    Mark scheme

    • A: partially permeable membrane — 1 mark
    • B: dialysis fluid — 1 mark
    • C: blood — 1 mark
  3. 3 Describe [4 marks]

    Describe how a dialysis machine removes urea from the blood of a patient.

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    Model answer

    The patient's blood flows on one side of a partially permeable membrane, and dialysis fluid flows on the other side. The dialysis fluid has no urea, so urea diffuses from the blood through the membrane into the fluid. Blood cells and proteins are too big to cross, so they stay in the blood. The cleaned blood returns to the patient.

    Mark scheme

    • Blood on one side of a partially permeable membrane, dialysis fluid on the other — 1 mark
    • Urea diffuses from the blood into the dialysis fluid — 1 mark
    • Blood cells and proteins cannot cross — 1 mark
    • The cleaned blood returns to the patient — 1 mark
  4. 4 Explain [3 marks]

    The dialysis fluid contains the same concentration of glucose as normal blood. Explain why.

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    Model answer

    If the concentrations of glucose are the same on both sides of the membrane, there is no net diffusion of glucose. The patient therefore does not lose glucose from the blood, as they would if there were none in the fluid.

    Mark scheme

    • Same concentration on both sides, so no net movement of glucose — 1 mark
    • The patient does not lose glucose — 1 mark
    • It would diffuse out if there were none in the fluid — 1 mark
  5. 5 Explain [3 marks]

    Explain why the dialysis fluid is kept flowing past the membrane instead of staying still.

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    Model answer

    The flow carries the urea away, so the concentration of urea in the fluid stays low. This keeps a steep concentration gradient across the membrane, so urea keeps diffusing out of the blood.

    Mark scheme

    • Flow carries the urea away — 1 mark
    • The urea concentration in the fluid stays low — 1 mark
    • A steep concentration gradient keeps urea diffusing out — 1 mark
  6. 6 Evaluate [4 marks]

    Evaluate the advantages and disadvantages of treating kidney failure by dialysis and by a kidney transplant.

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    Model answer

    Dialysis is available straight away and keeps the patient alive while they wait for a donor. However, it has to be repeated several times a week and restricts the patient's life. A transplant provides a working kidney and frees the patient from dialysis, but there are few donors, the kidney may be rejected, and the patient needs drugs for life, which increase the risk of infection.

    Mark scheme

    • Dialysis: advantage, such as available at once — 1 mark
    • Dialysis: disadvantage, such as repeated often — 1 mark
    • Transplant: advantage, such as no need for dialysis — 1 mark
    • Transplant: disadvantage, such as few donors / rejection / drugs — 1 mark
  7. 7 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 patient's immune system may recognise the new kidney as foreign and attack it, which is rejection. The drugs reduce the activity of the immune system, so the kidney is less likely to be rejected. They have to be taken for life because the risk does not go away.

    Mark scheme

    • The immune system may attack the new kidney — 1 mark
    • The drugs reduce the activity of the immune system — 1 mark
    • The risk of rejection continues — 1 mark

Quick check

  1. 1

    What does a dialysis machine remove from the blood?

    1. AGlucose
    2. BBlood cells
    3. CUrea
    4. DProtein
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    C: Urea

    Dialysis removes urea and excess ions from the blood.

  2. 2

    What separates the blood from the dialysis fluid?

    1. AA partially permeable membrane
    2. BA tube of glass
    3. CA layer of fat
    4. DA wall of cells
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    A: A partially permeable membrane

    A partially permeable membrane lets small molecules through but not blood cells or proteins.

  3. 3

    How does urea move from the blood into the dialysis fluid?

    1. ABy active transport
    2. BBy osmosis only
    3. CBy being pumped
    4. DBy diffusion
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    D: By diffusion

    Urea diffuses from a higher concentration in the blood to a lower concentration in the fluid.

  4. 4

    What is rejection?

    1. AThe failure of a dialysis machine
    2. BThe immune system attacking the new organ
    3. CThe loss of the donor
    4. DThe growth of the kidney
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    B: The immune system attacking the new organ

    Rejection is the attack of the immune system on a transplanted organ.

  5. 5

    Why do transplant patients take immunosuppressant drugs?

    1. ATo make the kidney work faster
    2. BTo clean the blood
    3. CTo reduce the risk of rejection
    4. DTo prevent diabetes
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    C: To reduce the risk of rejection

    The drugs reduce the activity of the immune system, so the new kidney is less likely to be rejected.

  6. 6

    Which is an advantage of dialysis over a transplant?

    1. AIt is available straight away
    2. BIt cures kidney failure
    3. CIt needs no machine
    4. DIt needs no time
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    A: It is available straight away

    Dialysis is available straight away, but a transplant needs a matching donor.

  7. 7

    Which is a disadvantage of a kidney transplant?

    1. AIt takes hours every week
    2. BIt uses a machine
    3. CIt removes glucose from the blood
    4. DThere are not enough donor kidneys
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    D: There are not enough donor kidneys

    There are not enough donors, and the kidney may be rejected.

  8. 8

    Why do blood cells stay in the blood in a dialysis machine?

    1. AThey are destroyed
    2. BThey are too big to cross the membrane
    3. CThey are carried away with the urea
    4. DThey are filtered out
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    B: They are too big to cross the membrane

    Blood cells are too big to pass through the partially permeable membrane.