# A patient is diagnosed with a condition in which their nephrons have been damaged, meaning that glucose and amino acids are lost in their urine. Explain why glucose and amino acids are normally absent from urine, describing the region of the nephron involved and the process that prevents their loss.

> WJEC A-Level Biology (Wales) — 4.5 Homeostasis and the kidney · Explain · 5 marks

> In a healthy kidney, the filtrate produced in the capillary knot contains small molecules including glucose, amino acids, urea, water and mineral ions. In a healthy person, glucose and amino acids do not appear in the final urine.

## Mark scheme (5 marks)

1. Glucose and amino acids are present in the filtrate after filtration at the capillary knot / glomerulus
2. Glucose and amino acids are removed from the filtrate by selective reabsorption
3. Selective reabsorption occurs in the kidney tubules / collecting duct
4. All glucose and amino acids are reabsorbed so none remain in the urine
5. In the damaged kidney, selective reabsorption cannot occur properly, so glucose and amino acids remain in the urine / are lost in urine

## Key terms

- [nephron](https://www.gradenine.co.uk/glossary/nephron)

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-patient-is-diagnosed-with-a-dc230f20) · Published by Druglandscape Ltd.