# Explain why oxygen moves from the lungs into the blood during breathing.

> Eduqas GCSE Biology — 1.1.2 Movement of substances · Explain · 4 marks

> Cells in the body constantly use oxygen during respiration. The blood arriving at the lungs has a low concentration of oxygen, while the air in the lungs has a high concentration of oxygen.

## Mark scheme (4 marks)

1. Identifies the process as diffusion
2. States that there is a concentration gradient / difference in concentration between the lungs and the blood
3. States that oxygen moves from a region of high concentration (lungs/air) to a region of low concentration (blood)
4. States that no energy is required / it is a passive process

## Related

- [Revision notes for Eduqas GCSE Biology](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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