# A researcher investigating membrane permeability treated red blood cells with a detergent that dissolves the phospholipid bilayer. Explain why this treatment caused haemoglobin to leave the cells but did not cause the loss of glucose-transport proteins from the cell contents.

> OCR A-Level Biology A (H420) — 2.5 Biological membranes · Explain · 4 marks

> Red blood cells are specialised cells that lack a nucleus and most membrane-bound organelles. They contain the oxygen-carrying protein haemoglobin dissolved in the cytoplasm and possess integral glucose-transport proteins embedded within their cell-surface membrane.

## Mark scheme (4 marks)

1. The phospholipid bilayer is dissolved/disrupted by the detergent, destroying the integrity of the cell-surface membrane.
2. Haemoglobin is a soluble protein dissolved in the cytoplasm, so once the membrane is destroyed it is free to leave the cell.
3. Glucose-transport proteins are integral/transmembrane proteins embedded within the phospholipid bilayer.
4. When the bilayer is dissolved by the detergent, the glucose-transport proteins are also removed/dispersed with the membrane material and are therefore not left behind in the cell contents.

## Key terms

- [phospholipid bilayer](https://www.gradenine.co.uk/glossary/phospholipid-bilayer)
- [haemoglobin](https://www.gradenine.co.uk/glossary/haemoglobin)

## Related

- [Revision notes for OCR A-Level Biology A (H420)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-researcher-investigating-membrane-permeability-treated-3f7346ab) · Published by Druglandscape Ltd.