An elongating ribosome is bound to appropriate tRNAs in both the A and P sites a

Question

An elongating ribosome is bound to appropriate tRNAs in both the A and P sites and is ready for peptidyl transfer. What happens next?

A. The carboxyl end of the polypeptide chain is released from the P-site tRNA and joined to the free amino group of the amino acid linked to the A-site tRNA.

B. The carboxyl end of the amino acid is released from the A-site tRNA and joined to the free amino group of the polypeptide chain linked to the P-site tRNA.

C. The tRNA with the growing peptide chain is translocated to the E-site where the amino acid from the A-site tRNA will be linked to the polypeptide chian.

D. The tRNA with the amino acid attached is translocated to the E-site before it is linked to the growing polypeptide chain.

A. The carboxyl end of the polypeptide chain is released from the P-site tRNA and joined to the free amino group of the amino acid linked to the A-site tRNA.

B. The carboxyl end of the amino acid is released from the A-site tRNA and joined to the free amino group of the polypeptide chain linked to the P-site tRNA.

C. The tRNA with the growing peptide chain is translocated to the E-site where the amino acid from the A-site tRNA will be linked to the polypeptide chian.

D. The tRNA with the amino acid attached is translocated to the E-site before it is linked to the growing polypeptide chain.

Explanation / Answer

answer A

In the elongation process, the ribosome peptidyl transferase centre catalyzes the aminolysis of an ester bond, where the -NH2 (Amino) group of A-site aminoacyl tRNA nucleophilically attacks the P-site peptidyl tRNA at the carbonyl carbon of the ester bond that links the peptide to the tRNA. Naturally Amines react fast because of their high nucleophilicity due to the presence of lone pair of electrons on nitrogen atom with esters to form peptide bonds. The ribosome accelerates this reaction by 106- to 107 times. so, the answer is A i.e., The carboxyl end of the polypeptide chain is released from the P-site tRNA and joined to the free amino group of the amino acid linked to the A-site tRNA.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.