Translation Flashcards
what is the role of tRNA?
carries a specific amino acid and has a complementary code to mRNA
what shape is a tRNA molecule?
3D L shape
describe the process of the amino acid attaching to the tRNA?
- enzyme with active site same shape as tRNA
- catalyses covalent bond between amino acid making it charged
what drives the forming of the covalent bond between amino acid and tRNA?
ATP hydrolysis
descibe flexible base pairing?
rule for base pairing between 3rd base of anti codon and codon is relaxed = wobble
what is the site for translation?
ribosomes
what are the 3 tRNA binding sites?
1) a site
2) P site
3) E site
what does the ribosome do?
catalyses formation of peptide bond
what do ribosomes consist of?
large sub unit and small sub unit made of proteins and ribosomal RNA
what are the 3 stages of building a polypeptide?
1) initiation
2) elongation
3) termination
what happens in the initiation stage?
mRNA binds to mRNA binding site on the small ribosome subunit
tRNA binds in P site of large ribosomal sub unit
What are 2 things that are required to bring all the components together for the initiation stage to happen?
- transcription factors
- GTP
What happens in the elongation stage?
- codon recognition - tRNA base pairs with complementary mRNA anticodon
- amino acids 1 by 1
- peptide bond formation between between polypeptide in P site and amino acid in A site
- Translocation - tRNA exits from E site
what start codon is the initiator of the polypeptide chain?
methionine
what happens during termination?
- when one of the 3 stop codons reaches the A site
- release factors bind to stop codon - causes hydrolysis of peptide bond
- polypeptide chain released into cytoplasm
what does the termination process require?
hydrolysis of 2 GTPs
what are protein called which help polypeptides fold correctly?
chaperones
which terminus are amino acids added to?
C terminus - carboxyl end
what are silent substitutions?
the replacement of a nucleotide which has no effect because it still codes for the same amino acid
what is missense substitutions?
altered codon still codes for an amino acid but not necessarily for the right one
what is a nonsense substitution?
cause translation to be terminated prematurely because codon now codes for stop codon not an amino acid
