Translation

Question 1

What are the 5 stages of protein synthesis?

Answer 1

Activation- formation of aminoacyl tRNA
Initiation- ribosomes assemble
Elongation
Termination
Post-transitional modification

Question 2

What is the structure of a prokaryotic ribosome?

Answer 2

70s made of 50s (2 RNA strands and 34 proteins) and 30s (1 RNA strand and 21 proteins)

Question 3

Whats is the structure of the eukaryotic ribosome?

Answer 3

80s made of 60s( 3 RNA strands and 49 proteins) and 40s (made of 1 RNA strand and 33 proteins).

Question 4

What is the function of each of the initiation factors?

Answer 4

IF1- prevents binding of non-initiating rRNA
IF2- travels into the cytoplasm and is associated with methionine in eukaryotes
IF3- prevents premature binding of RNA subunits.

Question 5

What is the first amino acid to be brought to the ribosome?

Answer 5

N-Formylmethionine is brought by tRNAf

Question 6

What is the initiation complex made of?

Answer 6

30S subunit, IF1, fMet

Question 7

What is the Shine-Dalgarno sequence?

Answer 7

It is the purine rich sequence on mRNA prior to the start codon that is complementary to the 3’ end sequence of 16S rRNA. It sets the reading frame.

Question 8

What are the energy requirements for protein synthesis?

Answer 8

Activation of aa- 2ATP –> 2AMP
Initiation- 1GTP/protein
Elongation- 2GTP/peptide bond
Release- 1GTP/protein

Question 9

How does the ribosome recogonise where to begin translation?

Answer 9

Shine-Dalgaro sequence in prokaryotes

5’ cap in eukaryotes.

Question 10

What are some post-transitional modifications?

Answer 10

• Hydroxylation of ser, thr, tyr
• Methylation of lys, glu
• Phosphorylation of ser, tyr
• Disulfide bond formation
• Proteolysis: proteolytic cleavage of amino acids.