4.2.5 Translation

Steps in Translation:

1. mRNA Attachment to Ribosome:

• The mRNA molecule binds to a ribosome in the cytoplasm.
• The ribosome reads the codons (triplets of bases) on the mRNA, starting at the start codon (AUG).

2. tRNA Brings Amino Acids:

• Transfer RNA (tRNA) collects specific amino acids from the cytoplasm and carries them to the ribosome.
• tRNA has:
• A binding site for one specific amino acid.
• A triplet of bases (anticodon), which is complementary to the mRNA codon.

3. Complementary Base Pairing:

• The anticodon on tRNA binds to its complementary codon on mRNA through base pairing.
• Two tRNA molecules can bind to the ribosome at the same time.

4. Formation of Peptide Bonds:

• The amino acids attached to the tRNA molecules are joined together by peptide bonds, catalysed by peptidyl transferase.
• After the bond forms, the tRNA molecule detaches, leaving the amino acid behind.

5. Polypeptide Chain Formation:

• The ribosome moves along the mRNA, allowing more tRNA molecules to attach and add amino acids to the growing chain.
• This process continues until a stop codon is reached on the mRNA. The stop codon does not code for an amino acid, and the ribosome releases the polypeptide chain.

6. Multiple Ribosomes:

• Several ribosomes, known as a polysome, can translate a single mRNA strand simultaneously, speeding up protein synthesis.