Translation

Question 1

What charges tRNA and how

Answer 1

aaRS and it has an active site for the 2 molecules- links them by ATP driven process when they’re bound to active site. Forms high energy ester bond. aaRS recognise tRNA by identifiers on acceptor stem.

Question 2

Formation of 43S pre-initiation complex

Answer 2

Addition of Met tRNA bound to eIF2 and GTP to 40S-eIF3 complex

Question 3

Formation of 43S initiation complex

Answer 3

43s Pre-initation complex binds to mRNA-eIF4 complex

Question 4

How is mRNA made circular

Answer 4

eIF4 complex binds to 5’ cap of mRNA and the pABP and bring them together to form a loop

Question 5

What happens when AUG start codon is reached

Answer 5

Triggers irreversible hydrolysis of GTP attached to eIF2, stops further unwinding

Question 6

What happens when small ribosomal subunit is positioned at the start codon and GTP has been hydrolysed

Answer 6

eIF 1,2,3,4 dissociate and 60S attaches, catalysed by eIF5. Met tRNA bound to AUG becomes P site

Question 7

aatRNA binding

Answer 7

aatRNA binds to A site by bp and brings eIF1a, GTP

Question 8

Conformational change

Answer 8

GTP in eIF1a,GTP hydrolyses, conformational change in ribosome , leading to tighter binding to the A site and release of eIF1a,GTP complex. Brings 2nd aatRNA closer to 1st

Question 9

Transpeptidation

Answer 9

2 AAs react and peptide bond forms, catalysed by peptidyltransferase. Peptide bond transferred to AA on A site

Question 10

Translocation

Answer 10

Ribosome moves distance of 1 codon, P site becomes E site. Monitored by hydrolysis of GTP

Question 11

Why does circular structure increase efficiency

Answer 11

recycling of ribosomes, ribosomes dissociating can quickly find 5’ end, multiple ribosomes, simultaneous translation

Question 12

Association of large subunit

Answer 12

When small subunit correctly positioned at AUG

Large subunit attached mediated by irreversible GTP hydrolysis and aided by eIF5