BIOL 2050 1nd Edition Lecture 26 Outline of Last Lecture I. Mutations Outline of Current Lecture I. Translationa. tRNAb. Ribosomesc. Polypeptidesd. Functional proteinCurrent LectureTranslation: genetic information flows from mRNA to proteintRNA: helps translate an mRNA message into a protein- Molecules of tRNA are not identicalo Codes for a specific amino acid at one endo Each has an anticodon on the other end Base pairs with a complementary codon on mRNA- Accurate translation requires two steps:o A correct match between tRNA and an amino acid, done by aminoacyl-tRNA synthetaseo A correct match between the tRNA anticodon and an mRNA codonRibosomes- Facilitate specific coupling of tRNA anticodons with mRNA codons in protein synthesis- Binding sites:o P site: holds the tRNA that carries the growing polypeptide chaino A site: hold the tRNA that carries the next amino acid to be added to the chaino E site: is the exit site, where discharged tRNAs leave the ribosomePolypeptide- Three stages:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Initiation: brings together mRNA, a tRNA with the first amino acid, and the two ribosomal subunitso Elongation: amino acids are added on one by one to the preceding amino acid at the C-terminus of the growing chain Steps- Codon recognition- Peptide bond formation- Translocation o Termination: when a stop codon in the mRNA reaches the A site of the ribosome. Addition of a water molecule instead of an amino acid Polypeptide is releasedo All three stages require protein factors that aid in the process- Polyribosomes: a number of ribosomes that translate an mRNA simultaneouslyFunctional Protein- Polypeptide chains are modified after translation or targeted to specific sites in the cell- Polypeptide chain spontaneously coils and folds into a three-dimensional shapeo Some are activated by enzymeso Others come together to form the subunits of a protein- Polypeptides destined for the ER or secretion are marked by a signal peptideo Signal-recognition particle: binds to a signal peptide Brings the signal peptide and its ribosome to the
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