Ribosomes are found in all living cells. Explain the role of ribosomes in protein synthesis, including how the sequence of amino acids in a protein is determined.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Every protein in an organism is assembled at a ribosome. The order in which amino acids are joined together determines the final shape and function of the protein.
Model answer (5 marks)
Ribosomes are the cellular sites where proteins are assembled.
mRNA, produced in the nucleus, carries the genetic information to the ribosome.
The ribosome reads the mRNA sequence of bases.
Each set of three bases (a codon) specifies a particular amino acid.
Amino acids are linked together in the order dictated by the codons, forming a polypeptide chain that folds into the final protein.
mRNA, produced in the nucleus, carries the genetic information to the ribosome.
The ribosome reads the mRNA sequence of bases.
Each set of three bases (a codon) specifies a particular amino acid.
Amino acids are linked together in the order dictated by the codons, forming a polypeptide chain that folds into the final protein.
Examiner tips
- Use the exact terms: ribosome, mRNA, codon, amino acid, polypeptide.
- Show the flow: nucleus → mRNA → ribosome → amino acids in codon order.
- Include the role of the ribosome as the assembly site.
- Keep each point brief and to the point.
Mark scheme (5 marks)
- Ribosomes are the site where proteins are made / assembled
- mRNA carries the genetic code from the nucleus to the ribosome
- The ribosome reads the sequence of bases on the mRNA
- Each sequence of three bases (a codon / triplet) codes for a specific amino acid
- Amino acids are joined together in a specific order / sequence to form a protein (polypeptide)
Key terms in this question
ribosome · amino acid · protein
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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