Lecture 6 Unit 1 Flashcards
what is tRNA responsible for
delivering the amino acid to the ribosome for addition to the growing polypeptide
what does each tRNA contain
the nucleotide CCA at its 3’ end, and the 3’ hydroxyl of the A is the attachment site for the amino acid
what does aminoacyl tRNA synthetase do
binds to one uncharged tRNA and its corresponding amino acid, it is responsible for charging tRNA
where do enzymes attach the amino acid to the tRNA?
at the 3’ end
what are the 3 phases in the process of translation
- initiation
- elongation
- termination
what does the ribosome do
determines the correct reading frame for the codons
what is the reading frame
where the ribosome begins reading the sequence of nucleotides
where is initiation located in prokaryotes
at the shine-dalgarno sequence
what is the shine-dalgarno sequence?
5’-AGGACGU-3’
can prokaryotes have polycistronic mRNA
yes
can eukaryotes have polycistronic mRNA
no, they have monocistronic mRNA
How does initiation start in eukaryotes
at the 5’ cap and AUG is the start codon
what happens during initiation
- complex scans for AUG codon
- initiation factors bind to 5’ cap
- initiation factors bring ip tRNA
- small subunit recruited
- initiation factors released
- large subunit joins complex
- next tRNA binds with the A site
- Met detaches from tRNA
- peptide bond is formed
- next tRNA binds with the A site
- ribosome shifts one codon
what happens during elongation
- tRNA in E site ejected
- new peptide bond joins polypeptide to tRNA
- small subunit moves one codon
- next tRNA comes into line
- large subunit moves over one codon
- tRNA in E site ejected
- new peptide bond joins polypeptide to tRNAG
- small subunit moves one codon
how is the energy required for the formation of peptide bonds obtained
by breaking the high energy bonds of GTP with elongation factors
