Ocr As Biology - Protein Synthesis (Translation)

Front 1

What is the second stage of protein synthesis (polypeptide synthesis)?

Back 1

Translation.

Front 2

Where in the cell does translation occur?

Back 2

Ribosomes in the cytoplasm.

Front 3

Give a basic description of what occurs during translation.

Back 3

Amino acids are joined together to make a polypeptide chain (protein), following the sequence of codons carried by the mRNA.

Front 4

[Part 1 of translation] Where does the mRNA strand go? What occurs there once the mRNA strand has reached its destination? Mention the enzymes involved.

Back 4

The mRNA attaches itself to a ribosome and transfer (tRNA) molecules carry amino acids to the ribosome.

Front 5

[Part 2 of translation] Once at the ribosome, what occurs between the mRNA strand and tRNA molecules? What is this process called?

Back 5

• A tRNA molecule with a anticodon that is complimentary to the start codon of the mRNA strand attaches itself.
• A second tRNA molecule does the same to the second codon on the mRNA strand.
• The codon pairing is called complementary base pairing.

Front 6

[Part 3 of translation] What occurs after the first two codons have been paired with tRNA molecules? What enzymes are involved in this process?

Back 6

• Ribosomal RNA (rRNA) in the ribosome catalyses the formation of a peptide bond between the two amino acids of the tRNA molecules.
• The first tRNA molecule moves away, leaving its amino acid behind.
• A third tRNA molecule binds to the next codon on the mRNA. Its amino acid binds together with the amino acid on the second tRNA molecule. Now the second tRNA molecule also moves away, leaving its amino acid behind.

Front 7

[Part 4 of translation] When does this process stop? What is formed at the end of this process.

Back 7

• The process continues producing the linked chain of amino acids (a polypeptide chain) until it reaches a stop codon on the mRNA.
• The newly formed polypeptide chain moves out of the ribosome and translation is complete.