Lecture 8 Flashcards
What is ATP broken down to in aminoacylation?
AMP + pyrophosphate
Where is the amino acid attached to?
3’ OH end of the adenine at the end of the acceptor arm
What is the names given to charged tRNA and uncharged tRNA?
Uncharged - tRNAser
Charged - Ser-tRNAser
Features of ribosomes
Complex of rRNA and proteins
Contain two subunits of unequal size
E. coli - 70S ribosome (50S large subunit + 30S small subunit)
Eukaryotes - 80S ribosome (60S large subunit + 40S small subunit)
Secondary structure
- space for mRNA and two tRNA molecules
- two tRNA binding sites
Ribosome attaches at the 5’ end of the mRNA
What are the sites found in the cleft of the ribosome?
A site - aminoacyl site where incoming aminoacyl-tRNA binds
P site - peptidyl site contains the peptidyl-tRNA with the growing polypeptide chain
E site - exit site where the previous tRNA leaves the ribosome
Describe the mechanism of translation?
Initiation - assemble of a ribosome on an mRNA
Elongation - repeated cycles of amino acid delivery, peptide bond for,action and translocation (movement of ribosome along mRNA strand)
Termination - the release of the completed polypeptide chain
What is a polysome?
Several ribosomes translating one mRNA at a time
Coupled transcription translation in prokaryotes, translation occurs when mRNA is being made
What is the difference between prokaryote and eukaryote translation?
Very similar in general; som differences in details of ribosome structure and each three stages of the process
What is post translational modification?
Altering the protein after it has been synthesised
- removal of N-terminal methionine
- formation of di-sulphide bonds
- proteolytic cleavage
- chemical modification
What is the product called when an amino acid joins to a tRNA?
What is it catalysed by and why do these enzymes have to be very specific?
Aminoacyl-tRNA
Catalyses by aminoacyl-tRNA synthetases
Specific because can’t afford any errors, 1% error would lead to 1 in every 100 amino acids being wrong
