Translation

Question 1

tRNA structure

Answer 1

~ simple cloverleaf structure
~ D-loop, T-loop and anti-codon loop
~ acceptor stem with a 3’ CCA tail
~ contains modified bases (T + D)

Question 2

3’ CCA tail

Answer 2

added post transcriptionally

site of amino acid attachment

Question 3

Aminoacylation/Charging

Answer 3

tRNA-amino acid attachment
~ uses ATP as a cofactor
~ a.a. attached to 3/2’ OH of terminal A of CCA tail
~ produces an aminoacyl-tRNA
~ each a.a./tRNA combo has its own enzyme

Question 4

Wobble pairing

Answer 4

when the 3rd base in the codon/anti-codon shows flexibility in its base pairing

Question 5

Method of specificity of aminoacyltransferases

Answer 5

1. size exclusion of a.a from aminoacylation site
2. editing pre-transfer in editing site (amino acid rejected)
3. editing post-transfer editing site breaks bonds

Question 6

IF1 and IF3

Answer 6

help guide the initiator tRNA to the right place on the small subunit
prevent binding of the large subunit

Question 7

EF-Ts

Answer 7

exchanges GDP for GTP, regenerating EF-Tu

Question 8

EF-Tu

Answer 8

elongation factor
~ forms a complex with GTP and aminoacyl-tRNA and helps it to bind tot he exposed codon in the A site
~ leaves after undergoing GTP hydrolysis

Question 9

EF-G

Answer 9

helps the ribosome move along one codon in the 3’ direction

~ released after GTP hydrolysis

Question 10

The peptide transferase reaction is catalysed by a …

Answer 10

ribozyme

Question 11

Ribozyme

Answer 11

RNA section of the 50S subunit of the ribosome

~ involved with rRNA splicing and the removal of introns

Question 12

Initiation

Answer 12

~ IF3 and IF1 are bound to the small ribosomal unit in the E and A sites
~ IF2 joins the mRNA and the small subunit together by hydrolysing GTP
~ a.a-tRNA binds to the P-site, releasing IF1-3 and causing the large ribosomal subunit to bind

Question 13

Elongation

Answer 13

~ repeated steps of tRNA binding
~ insertion of a.a-tRNA at A site dislodges the uncharged tRNA at E site
~ peptide chain gets longer

Question 14

Termination

Answer 14

~ when a stop codon is reached, a release factor (RF1 or RF2) binds to the stop codon in the A site

Question 15

Recycling

Answer 15

~ ribosome recycling factor and EFG-GTP promote complex disassembly
~ IF3 binds to small subunit to stabilise it