Presentation on theme: "Protein Synthesis and Controlled Protein Breakdown"— Presentation transcript:
1Protein Synthesis and Controlled Protein Breakdown Chapter 24Protein Synthesis and Controlled Protein Breakdown
2Chapter ObjectivesKnow the process of protein synthesis and the genetic code (don’t memorize the genetic code)Know how ribosomes workInitiation, elongation, terminationKnow the key steps in protein foldingUnderstand how protein translation is controlledKnow the process of protein degradation
3The Genetic Code Nonsense mutation – stop codon Degenerate code – more than one codon per amino acidConservation
4Overview of Protein Synthesis Amino acids are activated by aminoacyl synthetases using ATPAmino acids are added to tRNAtRNA molecules with their attached amino acid are brought to ribosomeThe growing peptide chain is added to each new amino acidEnergy cost = 1 ATP & 2 GTP
6tRNA Wobble Wobble allows for less tRNA molecules to be needed Notice orientation!!
7Amino Acid Attachment to tRNA Must attach correct amino acid to tRNAWrong amino acid will be incorporated into protein otherwiseSpecific aminoacyl-tRNA synthetase for each tRNA / amino acid pairNeed 20!No consistent recognitionSometimes anticodonSometimes other regions of tRNAAlways side chain of amino acidProcess driven by ATP hydrolysis
11Translation Initiation 30S ribosome subunit binds to Shine-Dalgarno sequence placing AUG in P siteSpecial met-tRNA recognizes IF2 (initiation protein factor 2)IF3 prevents binding of 50S subunit prematurelyShine-Dalgarno50S subunit then associatesIF2&3 are displacedGTP is hydrolyzed