Translation

Oct 7, 2024

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Lecture Notes on Protein Synthesis: Translation

Key Concepts

  • Translation: Process of converting the language of nucleic acids (mRNA) into the language of amino acids (proteins).
  • Involves:
    • Messenger RNA (mRNA): Synthesized in the nucleus, carries the genetic information.
    • Ribosomal RNA (rRNA): Part of the ribosome structure.
    • Transfer RNA (tRNA): Ferries amino acids to the ribosome.
    • Amino acids: Building blocks of proteins.

Stages of Protein Synthesis: Translation

Overview

  • Involves a cycle of events with multiple RNA types interacting.
  • Uses a triplet code (codon) on mRNA to specify amino acids.

Codon Table

  • Codons: Three-base sequences on mRNA coding for a specific amino acid.
  • Start codon: AUG (methionine).
  • Stop codons: UAA, UAG, UGA.
  • Some amino acids correspond to multiple codons.

Process of Translation

  1. Initiation

    • mRNA is recognized by the small ribosomal subunit.
    • Small subunit slides along mRNA to find the start codon (AUG).
    • Initiator tRNA with methionine binds to start codon.
    • Large ribosomal subunit binds, forming a complex.
    • mRNA fits into the ribosome like a zipper.

  2. Elongation

    • Ribosome has three sites: A (Acceptor), P (Peptidyl), E (Exit).
    • Initiator tRNA occupies P site; A site is ready for a new tRNA.
    • tRNA with complementary anticodon enters A site.
    • Peptide bond forms between amino acids at P and A sites.
    • Ribosome shifts, moving tRNA to E site, releasing it, and making space for the next tRNA.

  3. Termination

    • Process repeats until a stop codon is reached (e.g., UAG).
    • No tRNA matches the stop codon; instead, a dissociation complex causes the release of the protein.
    • Ribosomal subunits and mRNA dissociate, ready to start another round if needed.

Ribosomal and mRNA Complexes

  • Multiple ribosomes can translate a single mRNA simultaneously, increasing efficiency.

Visual Aids

  • Saladin's figure (page 122): Effective summary of translation steps.
    • Illustrates DNA, mRNA, tRNA, and resulting amino acid chain.

Study Tips

  • Understand the role of each RNA type in translation.
  • Familiarize with codon table and the process of matching codons to amino acids.
  • Practice with example questions, anticipating similar topics on quizzes/exams.

Note: Refer to Saladin pages 118-125 for detailed reading, especially the figure on page 121.