Translation Flashcards
Outline the mechanism by which tRNA becomes aminoacyl-tRNA - what is another term for this tRNA
- Aminoacyl-tRNA synthase binds to the correct AA using ATP and forming AMP
- tRNA binds to the AA displacing AMP
- ‘Charged tRNA’ is released from the enzyme
Some tRNA anticodons can bind to more than 1 mRNA codon - why?
Wobble hypothesis
What are ribosomes made up of
rRNA and proteins
Which subunit of a ribosome binds to what and how do they differ in P and E
Large - tRNA
Small - mRNA
P - 70s - 50s + 30s
E - 80s - 60s + 40s
Ribosomes have 4 binding sites - 1 for mRNA and 3 for tRNA - describe the 3 for tRNA
P-site - Holds the tRNA carrying the growing polypeptide chain
A-site - Holds the tRNA carrying the next AA to be added to the chain
E-site - Site where tRNA exits the ribosome
What are the 3 phases of Translation
Association and initiation
Elongation
Termination
Outline the 1st step in translation - What is the name of the complex formed
- Small subunit binds to mRNA along with initiation factors and specific initiator tRNA with anticodon AUG
- Large ribosomal subunit joins to tRNA forming the ‘Translational Initiation Complex’
There is a 3-step cycle in elongation - outline each phase
1. Codon recognition
2. Peptide bond formation
3. Translocation
- The anticodon of charged tRNA base pairs with complementary codon in A site
- Large subunit catalyses the formation of a peptide bond between the new AA in the A site and the AA in the P site
- This removes the polypeptide from the tRNA in the P site and attaches it to the AA in the A site
- The ribosome translocates the tRNA in the A site to the P site and the empty tRNA in the P site is moved to the E site where it is released
Outline the termination of translation
- When the ribosome reaches a stop codon on the mRNA the A site accepts a release factor
- This factor breaks bond between tRNA molecule and the polypeptide in the P site
Give 1 example of post-translational modification
N-terminus of the AA is removed or modified
