# Explain why RNA is described as a single-stranded molecule and outline how this structural feature relates to the functional diversity of RNA molecules within a cell.

> IB DP Biology Standard Level (2023 syllabus) — A1.2 Nucleic acids · Explain · 4 marks

## Mark scheme (4 marks)

1. RNA consists of a single polynucleotide strand (rather than two complementary strands held together by hydrogen bonds between bases)
2. The single strand can fold back on itself, forming localised complementary base pairs / hairpin loops / three-dimensional shapes
3. This folding ability allows tRNA to adopt a specific cloverleaf / L-shaped structure that enables it to carry amino acids and recognise codons during translation
4. mRNA functions as a linear template / carries a sequence of codons read by ribosomes, and rRNA has a structural and catalytic role in ribosomes — accept any named RNA type with a correct functional link

## Key terms

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

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](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/explain-why-rna-is-described-as-2d88b875) · Published by Druglandscape Ltd.