Presentation on theme: "Chapter 24 Protein Synthesis and Controlled Protein Breakdown."— Presentation transcript:
Chapter 24 Protein Synthesis and Controlled Protein Breakdown
Chapter Objectives Know the process of protein synthesis and the genetic code (don’t memorize the genetic code) Know how ribosomes work – Initiation, elongation, termination Know the key steps in protein folding Understand how protein translation is controlled Know the process of protein degradation
The Genetic Code Nonsense mutation – stop codon Degenerate code – more than one codon per amino acid Conservation
Overview of Protein Synthesis 1.Amino acids are activated by aminoacyl synthetases using ATP – Amino acids are added to tRNA 2.tRNA molecules with their attached amino acid are brought to ribosome 3.The growing peptide chain is added to each new amino acid 4.Energy cost = 1 ATP & 2 GTP
tRNA Wobble Wobble allows for less tRNA molecules to be needed Notice orientation!!
Amino Acid Attachment to tRNA Must attach correct amino acid to tRNA – Wrong amino acid will be incorporated into protein otherwise Specific aminoacyl-tRNA synthetase for each tRNA / amino acid pair – Need 20! No consistent recognition – Sometimes anticodon – Sometimes other regions of tRNA – Always side chain of amino acid Process driven by ATP hydrolysis
Translation Initiation Shine-Dalgarno 30S ribosome subunit binds to Shine-Dalgarno sequence placing AUG in P site Special met-tRNA recognizes IF2 (initiation protein factor 2) IF3 prevents binding of 50S subunit prematurely 50S subunit then associates IF2&3 are displaced GTP is hydrolyzed