# A biochemist is studying the structure of DNA. She notes that DNA is a natural polymer made from nucleotide monomers joined together by condensation polymerisation. Explain why DNA is described as a condensation polymer, and compare the type of polymerisation used to make DNA with addition polymerisation.

> OCR A-Level Chemistry A (H432) — 6.2 Nitrogen compounds, polymers and synthesis · Explain · 5 marks

> DNA is a naturally occurring polymer found in the nuclei of cells. It is formed when nucleotide monomers join together in a condensation polymerisation reaction. Addition polymerisation is another type of polymerisation used to make many synthetic polymers.

## Mark scheme (5 marks)

1. In condensation polymerisation, monomers join together and lose small molecules
2. The monomers in condensation polymerisation have two functional groups
3. In addition polymerisation, monomers join together without losing any small molecules / no by-products are produced
4. Addition polymerisation uses monomers that contain a carbon–carbon double bond / are unsaturated (alkenes)
5. DNA can be described as a condensation polymer because the nucleotide monomers join together releasing small molecules / water, forming long polymer chains

## Key terms

- [condensation polymerisation](https://www.gradenine.co.uk/glossary/condensation-polymerisation)
- [addition polymerisation](https://www.gradenine.co.uk/glossary/addition-polymerisation)
- [monomers](https://www.gradenine.co.uk/glossary/monomers)
- [polymer](https://www.gradenine.co.uk/glossary/polymer)

## Related

- [Revision notes for OCR A-Level Chemistry A (H432)](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-biochemist-is-studying-the-structure-633f1e82) · Published by Druglandscape Ltd.