State the substances that are filtered out of the blood at the glomerulus, and explain what happens to these substances as they pass along the renal tubule.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Glucose, ions (e.g. Na⁺, K⁺, Cl⁻) and water are filtered at the glomerulus. All glucose is reabsorbed in the proximal tubule, and most water is reabsorbed in the proximal tubule and descending limb of the loop of Henle. Urea and any excess ions and water remain in the tubular fluid and become part of the urine.
Examiner tips
- Use the exact terms "glucose, ions, water" for the filtered substances. Show the sequence: filtered → reabsorbed (glucose, water) → remains (urea, excess ions, water).
- Mention the proximal tubule for glucose and water reabsorption and the loop of Henle for water reabsorption.
Mark scheme (4 marks)
- Names substances filtered at the glomerulus
- All glucose is reabsorbed back into the blood
- Most water is reabsorbed back into the blood
- Urea (and excess ions/water) remain in the tubule and form urine
Key terms in this question
Related
- All Cambridge International IGCSE Biology (0610) revision notes →
- How to answer a "State and Explain" question →
- Decode the mark scheme abbreviations →