Translation

Question 1

Translation

Answer 1

Occurs when the sequence of codons on the mRNA is used to assemble a specific sequence of amino acids into a polypeptide chain, at the ribosomes

Question 2

Ribosomes and tRNA

Answer 2

Two sub-units made of protein and rRNA:

• Large sub-unit with two tRNA attachment sites and one release site
• Small sub-unit that binds to mRNA

Each tRNA molecule carries a specific amino acid

Question 3

Stages of Translation

Answer 3

1) Initiation
2) Elongation
3) Termination

Question 4

Initiation

Answer 4

• mRNA is attached to a ribosome at the start codon (AUG)
• The first tRNA molecule with complementary anticodon pairs with the start codon
• Hydrogen bonds form between complementary base pairs of the codon and anti codon

Question 5

Elongation

Answer 5

• Peptide bonds form between amino acids on tRNA molecules
• The first tRNA leaves the ribosome, emptying the attachment site but leaving its amino acid attached via peptide bonds
• The ribosome moves one codon along the mRNA and the next tRNA binds

Question 6

Termination

Answer 6

• The elongation process continues until a stop codon is reached
• The ribosome, mRNA and polypeptide chain all separate

Question 7

Post-Translational Modifications

Answer 7

Modifications include:

• Glycoproteins (Protein + Carbohydrate)
• Lipoproteins (Protein + Lipid)
• Phosphoprotein (Protein + Phosphate)

Polypeptides can also be combined as shown by Haemoglobin