# Explain the role of ribosomes in translation during protein synthesis.

> IB DP Biology Standard Level (2023 syllabus) — D1.2 Protein synthesis · Explain · 4 marks

## Mark scheme (4 marks)

1. Ribosomes are composed of two subunits (large and small) that assemble around the mRNA.
2. The ribosome moves along the mRNA (5′ to 3′) reading successive codons.
3. The ribosome holds tRNA molecules in place (at A and P sites) so that complementary base pairing between codons and anticodons can occur.
4. The ribosome catalyses peptide bond formation between adjacent amino acids, elongating the polypeptide chain.

## Key terms

- [ribosome](https://www.gradenine.co.uk/glossary/ribosome)
- [translation](https://www.gradenine.co.uk/glossary/translation)

## 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-the-role-of-ribosomes-in-7ec5bef9) · Published by Druglandscape Ltd.