Pearson Edexcel · GCSE · Biology
Course version: 1BI0 · Version from Sept 2016
7.21B Describe the treatments for kidney failure, including kidney…
Full specification wording
Topic 7 – Animal coordination, control and homeostasis: 7.21B Describe the treatments for kidney failure, including kidney dialysis and organ donation
Kidney failure means the kidneys no longer adequately remove urea and balance water and ions, so treatment must replace that filtering role.
Checked against the Pearson Edexcel 1BI0 specification (opens in a new tab) on .
- Point 18 of 19
Study notes
From the checked teaching notes for this specification point.
The idea
Kidney failure means the kidneys no longer adequately remove urea and balance water and ions, so treatment must replace that filtering role. Dialysis does this outside the body: blood is drawn from the patient, passed through a dialysis machine containing partially permeable tubing surrounded by dialysis fluid, and returned. The fluid has the same concentration of useful substances such as glucose and mineral ions as the blood, so these are not lost, but it contains no urea, so urea diffuses out of the blood down its concentration gradient. Dialysis must be repeated regularly because waste builds up between sessions. Organ donation is a longer-term treatment: a donated kidney is transplanted so the patient regains working kidneys and no longer needs dialysis, but the immune system may reject the organ, so immunosuppressant drugs are needed and a suitable donor must be available.
What earns the marks
- Dialysis removes urea from the blood by diffusion across a partially permeable membrane into dialysis fluid that contains no urea, maintaining a concentration gradient.
- Dialysis fluid has the same concentration of glucose and mineral ions as the blood so useful substances are not lost from the blood.
- Dialysis must be carried out regularly (several sessions per week) because waste products build up between treatments.
- Organ donation (kidney transplant) replaces the failed kidney so the patient no longer needs dialysis.
- A transplanted kidney may be rejected by the immune system, so immunosuppressant drugs are required and a matched donor must be available.
Common mistakes and how to put them right
Thinking dialysis fluid should contain urea.
Put it right: The fluid contains no urea so urea diffuses out of the blood.
Believing dialysis cures kidney failure permanently.
Put it right: Dialysis is a repeated treatment, whereas a successful transplant can restore kidney function long term.
Assuming a transplant needs no medication.
Put it right: Immunosuppressant drugs reduce the risk of rejection of the donated organ.
Exam tips
- Link each treatment to the kidney's normal job of removing urea and balancing water and ions.
- For dialysis, name the direction of diffusion of urea and explain why the fluid's glucose and ion concentrations matter.
- For donation, state both the benefit (no further dialysis) and the drawback (risk of rejection and need for immunosuppressants).
Try the lesson
The start of the Topic 7 – Animal coordination, control and homeostasis: 7.21B Describe the treatments for kidney failure, including kidney dialysis and organ donation lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement describes what kidney dialysis does for a person whose kidneys have failed?
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