What mistakes do students make with Describe the function of kidneys in maintaining the…?

Saying the kidneys make water. Put it right by stating they reabsorb water from the filtrate. Confusing water balance with temperature regulation. Put it right by focusing on water content of body fluids. Stating that urine concentration stays constant. Put it right by linking it to water reabsorption.

What are the exam tips for Describe the function of kidneys in maintaining the… in Biology AQA GCSE?

Use the terms reabsorption, filtrate and urine concentration. Give a cause-and-effect chain: blood concentration → water reabsorption → urine concentration. Include a specific example such as drinking little water or sweating heavily.

AQA · GCSE · Biology

Course version: 8461 · Version from Sept 2018

Students should be able to describe the function of kidneys in maintaining…

Full specification wording

Maintaining water and nitrogen balance in the body (biology only): Students should be able to describe the function of kidneys in maintaining the water balance of the body.

The kidneys maintain water balance by adjusting how much water is reabsorbed from the filtrate back into the blood, so that the volume and concentration of body fluids stay within a safe range.

Checked against the AQA 8461 specification (opens in a new tab) on 21 September 2026.

Point 10 of 17
2 key terms

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

The kidneys regulate the water content of body fluids.
Water is reabsorbed from the filtrate back into the blood.
The amount of water reabsorbed determines urine concentration and volume.
When blood is too concentrated, more water is reabsorbed and a smaller volume of concentrated urine is produced.
When blood is too dilute, less water is reabsorbed and a larger volume of dilute urine is produced.

Common mistakes and how to put them right

Saying the kidneys make water.
Put it right by stating they reabsorb water from the filtrate.
Confusing water balance with temperature regulation.
Put it right by focusing on water content of body fluids.
Stating that urine concentration stays constant.
Put it right by linking it to water reabsorption.

Exam tips

Use the terms reabsorption, filtrate and urine concentration.
Give a cause-and-effect chain: blood concentration → water reabsorption → urine concentration.
Include a specific example such as drinking little water or sweating heavily.

Try the lesson

The start of the Maintaining water and nitrogen balance in the body (biology only): Students should be able to describe the function of kidneys in maintaining the water balance of the body. lesson, made from checked teaching notes for this specification point.

Have a go first

Which statement describes the function of the kidneys in maintaining the water balance of the body?

Tip: press 1 to 4 to choose

Listen

The kidneys maintain water balance by adjusting how much water is reabsorbed from the filtrate back into the blood, so that the volume and concentration of body fluids stay within a safe range. If the blood is too concentrated, more water is reabsorbed and a small volume of concentrated urine is produced. If the blood is too dilute, less water is reabsorbed and a large volume of dilute urine is produced. For example, after drinking little water on a hot day, the kidneys conserve water and urine becomes darker and more concentrated. This keeps cells at a suitable concentration so they function properly. A strong answer earns marks for these points. The kidneys regulate the water content of body fluids. Water is reabsorbed from the filtrate back into the blood. The amount of water reabsorbed determines urine concentration and volume. When blood is too concentrated, more water is reabsorbed and a smaller volume of concentrated urine is produced. A common slip: Saying the kidneys make water. Instead, stating they reabsorb water from the filtrate. Exam tip: Use the terms reabsorption, filtrate and urine concentration.

See it

A top-to-bottom flowchart with two parallel chains that join at the end. The left chain starts with a box reading 'Blood too concentrated', which leads to 'More water reabsorbed from filtrate into blood', then to 'Small volume of concentrated urine produced'. The right chain starts with 'Blood too dilute', which leads to 'Less water reabsorbed from filtrate into blood', then to 'Large volume of dilute urine produced'. Both final urine boxes lead into a single box reading 'Water content of body fluids kept in safe range'. — It shows how the kidneys adjust water reabsorption from the filtrate to produce concentrated or dilute urine and so keep the water content of body fluids in a safe range.

Key words

Say what each word means before you turn the card.

Kidney function

Try answering aloud or in your head before turning the card.

Reabsorption

Try answering aloud or in your head before turning the card.

See every definition

Kidney function: The kidneys regulate the water content of body fluids by adjusting how much water is reabsorbed from the filtrate back into the blood.
Reabsorption: Water is reabsorbed from the filtrate back into the blood, and the amount reabsorbed determines urine concentration and volume.

Label the diagram

Some boxes have lost their names. Pick the right name for each number.

The diagram again, with 3 boxes numbered instead of named. A top-to-bottom flowchart with two parallel chains that join at the end. The left chain starts with a box reading 'Blood too concentrated', which leads to 'More water reabsorbed from filtrate into blood', then to 'Small volume of concentrated urine produced'. The right chain starts with 'Blood too dilute', which leads to 'Less water reabsorbed from filtrate into blood', then to 'Large volume of dilute urine produced'. Both final urine boxes lead into a single box reading 'Water content of body fluids kept in safe range'.

1Box 1
2Box 2
3Box 3

0 of 3 labelled

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