Translation Flashcards
To be able to describe the function and structure of both prokaryotic and eukaryotic ribosomes To comprehend the sequence of events during protein synthesis Describe the events which can modify a protein after is has been synthesised State examples of antibiotics which specifically inhibit protein synthesis in both types of cells
What are the 5 key roles of ribosomes?
- Binds to mRNA - allows codons to be read
- Includes binding sites for tRNA molecules
- Mediate the interaction of non-ribosomal protein factors
- Catalyse peptide bond formation
- Be capable of movement
What are the 3 prokaryotic ribosome binding sites?
A site - aminoacyl site
P site - peptidyl site
E site - exit site
What energy sources are required for translation?
ATP and GTP
How many amino acids are there?
20
What part of the chain does growth occur?
P site and A site
What happens at the E site?
Uncharged tRNA moves to the E site
What is the difference between prokaryotic and eukaryotic coding region?
Prokaryotic can have more than 1 - polycistronic
Eukaryotic only have 1 - monocistronic
What occurs in the initiation phase of translation? (2)
Ribosomes recognise start codon
Initiation AUG codon is recognised by special tRNA - P site
What occurs in the elongation phase of translation? (3)
- Involves addition of amino acids to the carboxyl end of the growing chain
- Delivery of the next aminoacyl-tRNA (GTP hydrolysis)
- The ribosome then advances 3 nucleotides to mRNA end (translocation) (P to E site and A to P site)
What occurs in the termination phase of translation? (2)
Termination codons are recognised by release factors
RF binding causes hydrolysis of bond linking peptide to tRNA site
What is a translation inhibitor? (3)
Streptomycin - member of the ahminoglycosides
Ribosomes misread
Prevents chain initiation (cell death)
What are 2 protein synthesis inhibitors?
Chloramphenicol - inhibits peptidyltransferase activity
Tetracycline - prevents aminoacyl-tRNA into A-site
What happens at post-translational modification? (3)
Ribosome associated chaperones help fold protein
Polypeptide chains are modified
Phosphorylation occurs
