8.5 Polypeptide synthesis - translation

Question 1

What is translation?

Answer 1

The production of polypeptides from the sequence of codons carried by mRNA.

Question 2

What are the stages of translation?

Answer 2

1. ribosome attaches to the starting codon of one end of a mRNA strand
2. a tRNA molecule that carries a specific amino acid and with a complementary anticodon sequence binds to the mRNA
3. another tRNA molecule that carries another specific amino acid and with a complementary anticodon binds to the next mRNA codon
4. the ribosome moves along the mRNA and brings two tRNA molecules together at one time
5. the amino acids carried by the first two tRNA molecules are linked together by a peptide bond using an enzyme and ATP which is hydrolysed to release energy
6. the ribosome moves to the third codon and links the amino acids on the second and third tRNA molecule
7. the first tRNA molecule is released from its amino acid and is free to collect another amino acid for future use
8. stage 5 to 7 is repeated until a polypeptide chain is built up
9. the synthesis of a polypeptide chain continues until the ribosome reaches a stop codon on mRNA
10. the completed polypeptide chain separates from the ribosome

Question 3

What are the roles of ATP in translation?

Answer 3

1. provide energy to attach to amino acids to tRNA
2. attach amino acids together