Translation

Study Notes

Translation is the process by which the genetic code in mRNA is used to synthesize proteins. It involves several stages including initiation, elongation, translocation, and termination, each with specific roles in protein synthesis.

• Initiation — the assembly of mRNA, tRNA, and ribosome components to start translation.
  Example: The small ribosomal subunit binds to the mRNA's start codon.
• Elongation — the addition of amino acids to the growing polypeptide chain.
  Example: A peptide bond forms between amino acids in the ribosomal A and P sites.
• Translocation — the movement of the ribosome along the mRNA strand.
  Example: The ribosome shifts one codon, moving tRNA from the A site to the P site.
• Termination — the release of the polypeptide chain and disassembly of translation components.
  Example: A release factor binds to the stop codon, ending translation.
• Free ribosomes — ribosomes that synthesize proteins for use within the cell.
  Example: Found in the cytosol, not attached to the ER.
• Bound ribosomes — ribosomes that synthesize proteins for secretion or use in lysosomes.
  Example: Attached to the rough ER in eukaryotic cells.
• tRNA Activation — the process of attaching an amino acid to tRNA.
  Example: A tRNA-activating enzyme catalyzes the binding of an amino acid to tRNA.

Exam Tips

Key Definitions to Remember

• Initiation
• Elongation
• Translocation
• Termination
• Free ribosomes
• Bound ribosomes
• tRNA Activation

Common Confusions

• Mixing up the roles of free and bound ribosomes
• Confusing the stages of translation with transcription

Typical Exam Questions

• What is the role of the ribosome in translation? The ribosome facilitates the binding of tRNA to mRNA and catalyzes peptide bond formation.
• How does tRNA become charged? tRNA is charged by binding with a specific amino acid through a tRNA-activating enzyme.
• What happens during the termination stage of translation? A release factor binds to the stop codon, releasing the polypeptide chain and disassembling the ribosome.

What Examiners Usually Test

• Understanding of the translation process and its stages
• Differences between free and bound ribosomes
• The role of tRNA in protein synthesis