Protein Synthesis

Question 1

Describe the structure of prokaryotic ribosomes.

Answer 1

. 70S
. 2 subunits, one small and one large

. 3 sites: A, P, E
. A site (aminoacyl site) - Where incoming tRNA binds
. P site (peptidyl site) - Where tRNA attached to growing peptide chain binds
. E site (exit site) - Where tRNA leaves

Question 2

Describe the structure of eukaryotic ribosomes.

Answer 2

. 80S

. 2 subunits, one small and one large

Question 3

Name the three stages of translation.

Answer 3

Initiation, elongation, termination

Question 4

Compare the coding regions of eukaryotic and prokaryotic mRNA.

Answer 4

Prokaryotic mRNA is polycistronic (can have more than one coding region, each with its own initiation and termination codons
Eukaryotic mRNA is monocistronic (just has one coding region)

Question 5

Give the base sequence of the start codon.

Answer 5

AUG

Question 6

During the elongation stage of translation, where are amino acids added to the polypeptide chain?

Answer 6

Amino acids are added to the carboxyl end of the polypeptide chain

Question 7

What causes the newly-translated protein to be released from the E site in the termination stage of translation?

Answer 7

Release factor (RF) hydrolyses the bond between tRNA and the peptide, releasing the protein

Question 8

What happens when a protein is ubiquitinated?

Answer 8

Ubiquitin added, which sends protein for degradation