Protein Synthesis Flashcards
Describe what happens in transcription
Pre-mRNA
Introns removed
Exons = mRNA
What are the major components in translation?
Ribosomes tRNA Aminoacyl-tRNA synthetases mRNA molecules Protein factors (facilitators)
What are the sites found in ribosomes?
E-site = exit (where tRNA leaves) P-site = peptidyl (where peptides grow) A-site = amino acyl (where incoming amino acids enter)
What do prokaryotes have?
70s ribosomes
= 30s subunit + 50s subunit
What do eukaryotes have?
80s ribosomes
= 40s subunit + 60s subunit
Describe initiation
Translation
tRNA binds to small ribosomal unit
Complex scans to find start codon
Initiator tRNA binds to start codon
Large ribosomal subunit joins to form initiation complex
How many codons is there?
64
How many amino acids is there?
20
Describe elongation
Translation
mRNA shifted forward, exposing new codon
tRNA binds to matching codon
Polypeptide is linked to new amino acid
Describe secondary structure of tRNA
Amino acid attachment site
Anti-codon
Clover leaf structure
Base pairing
Describe tertiary tRNA structure
L shaped tRNA
Single conformation of tRNA increases efficiency of binding within ribosome
Amino acid in correct position for formation of peptide bonds
How is aminoacyl-tRNA formed?
ATP + amino acid —-> aminoacyl-AMP —-> aminoacyl-tRNA
What does aminoacyl-tRNA do?
Allows tRNA to pick up amino acid using ATP
Describe termination
Translation
Ribosome reaches stop codon on MRNA
The A site of ribosome accepts protein called release factor instead of tRNA
Hydrolyses bod between tRNA + P site + last amino acid of polypeptide
2 ribosomal subunits + other components of assembly dissociate
Describe GM insulin
Bacteria with plasmid
Insert gene that makes insulin into it
What are the post-translational modification of proteins?
Proteolysis
Glycosylation
Phosphorylation
What is proteolysis?
Polypeptide chain is cleaved into fragments which takes on different shapes
What is glycosylation?
The addition of sugars to polypeptide chains
Important in targeting + recognition
What is phosphorylation?
The addition of phosphate groups
Often changes the shape of protein, exposing an active site of an enzyme or binding site for another molecule
What happens in post-translational modification of proteins?
Leader sequence aids transfer of polypeptide over membrane
After transfer leader sequence removed by cleavage
Proinsulin folds into favourable conformation
Disulphide bonds form
Connective sequence cleaved + active form of insulin observed
