Biology • Year 12 • Module 5 • Lesson 11
Translation — From mRNA to Polypeptide
Lock in the core vocabulary of translation, separate the roles of mRNA, tRNA and the ribosome, and master codon-anticodon pairing before tackling the apply tier.
1. Term–definition match
The ten definitions below are shuffled. In the right-hand column write the matching term from this list: translation, ribosome, mRNA, tRNA, codon, anticodon, peptide bond, polypeptide, amino acid, polypeptide elongation. 10 marks
| # | Definition (shuffled) | Matching term |
|---|---|---|
| 1.1 | A three-base sequence on mRNA that specifies one amino acid in the polypeptide chain. | |
| 1.2 | A monomer that joins to others by covalent bonds to form a polypeptide. | |
| 1.3 | The process of using the mRNA code to assemble a polypeptide. | |
| 1.4 | A three-base sequence on tRNA that pairs with a complementary codon on mRNA. | |
| 1.5 | The molecule that is read by the ribosome and that carries codons copied from a gene. | |
| 1.6 | A chain of amino acids joined in a sequence determined by the genetic code. | |
| 1.7 | The site in the cytoplasm where mRNA is read and amino acids are joined. | |
| 1.8 | The covalent bond that links adjacent amino acids in a polypeptide. | |
| 1.9 | The transfer RNA molecule that carries a specific amino acid to the ribosome. | |
| 1.10 | The repeating cycle of codon matching, amino acid delivery and peptide bond formation that lengthens the chain. |
2. True or false — with correction
For each statement, circle T or F. If the statement is false, write the corrected version on the line below. 12 marks (1 for T/F, 1 for the correction where needed)
2.1 Translation occurs in the nucleus, where the DNA is stored. T / F
2.2 mRNA carries codons; tRNA carries amino acids and has an anticodon. T / F
2.3 The ribosome reads the mRNA one base at a time. T / F
2.4 The anticodon on a tRNA is identical to the codon it pairs with on the mRNA. T / F
2.5 Peptide bonds link adjacent amino acids in the growing polypeptide. T / F
2.6 Each tRNA molecule carries a different amino acid every time it is reused. T / F
3. Function recall
Answer each in 1–2 sentences using precise terms from the lesson. 10 marks (2 each)
3.1 What is the function of the ribosome in translation?
3.2 What is the function of tRNA in translation?
3.3 What is the function of codon-anticodon pairing at the ribosome?
3.4 What is the function of the peptide bond during polypeptide elongation?
3.5 What is the function of translation for the cell as a whole?
4. Cloze — fill the blanks
Complete the paragraph below using each term from the word bank once. 10 marks (1 per blank)
Word bank: ribosome · codons · anticodon · amino acid · peptide bond · tRNA · mRNA · cytoplasm · polypeptide · complementary
During translation, the (4.1) ______________ that was transcribed in the nucleus moves out into the (4.2) ______________ and binds to a (4.3) ______________. The ribosome reads the message three bases at a time as (4.4) ______________. Each (4.5) ______________ molecule carries one specific (4.6) ______________ at one end and has an (4.7) ______________ at the other end. The anticodon pairs with a (4.8) ______________ codon on the mRNA. Once two amino acids are held next to each other at the ribosome, a (4.9) ______________ forms between them. As this process repeats codon by codon, a growing (4.10) ______________ is assembled.
Q1 — Term–definition matches (10 marks)
1.1 codon • 1.2 amino acid • 1.3 translation • 1.4 anticodon • 1.5 mRNA • 1.6 polypeptide • 1.7 ribosome • 1.8 peptide bond • 1.9 tRNA • 1.10 polypeptide elongation.
Marking notes. 1 mark per correct match.
Q2 — True / false with correction (12 marks)
2.1 False. Correction: translation occurs in the cytoplasm at ribosomes (on the rough ER for secreted proteins, or free in the cytoplasm); transcription occurs in the nucleus, but mRNA must be exported before it can be translated. [1 + 1]
2.2 True. [1] (No correction needed — this is the lesson's central exam trap.)
2.3 False. Correction: the ribosome reads mRNA three bases at a time — each three-base unit is a codon that specifies one amino acid. [1 + 1]
2.4 False. Correction: the anticodon is complementary to the codon, not identical (e.g. anticodon UAC pairs with codon AUG). [1 + 1]
2.5 True. [1]
2.6 False. Correction: each tRNA has a fixed anticodon and is charged with one specific amino acid that corresponds to that codon; it carries the same amino acid each time, not a different one. [1 + 1]
Marking notes. 1 mark for correct T/F, 1 mark for the correction where the statement is false (no correction required if true).
Q3 — Function recall (10 marks)
3.1 Ribosome (2): The ribosome binds to mRNA in the cytoplasm and reads the codon sequence three bases at a time; it also coordinates tRNA pairing and catalyses peptide bond formation between adjacent amino acids.
3.2 tRNA (2): Each tRNA brings one specific amino acid to the ribosome and uses its anticodon to pair with the matching codon on mRNA, so that amino acids arrive in the order specified by the genetic code.
3.3 Codon-anticodon pairing (2): Pairing between the tRNA anticodon and the complementary mRNA codon ensures the correct amino acid is placed in the correct position in the growing polypeptide, so the amino acid sequence reflects the mRNA sequence.
3.4 Peptide bond (2): Peptide bonds covalently link adjacent amino acids in the chain so that the polypeptide stays joined together as it elongates and the ribosome moves on to the next codon.
3.5 Translation (2): Translation converts the coded information in mRNA into a specific amino acid sequence, producing the polypeptides needed for enzymes, structural proteins, transport proteins and signalling proteins.
Marking notes. 1 mark per relevant point, max 2 per item.
Q4 — Cloze (10 marks)
4.1 mRNA • 4.2 cytoplasm • 4.3 ribosome • 4.4 codons • 4.5 tRNA • 4.6 amino acid • 4.7 anticodon • 4.8 complementary • 4.9 peptide bond • 4.10 polypeptide.
Marking notes. 1 mark per correct term. Accept "transfer RNA" for tRNA and "messenger RNA" for mRNA.