What roles do the ribosome and initiation/elongation/termination factors play in translation?

• A. The ribosome's small and large subunits provide the catalytic center; initiation factors assemble the complex; elongation factors deliver tRNAs and promote peptide bond formation; termination factors recognize stop codons to release the polypeptide.
• B. The ribosome acts as a transporter; initiation factors decap the mRNA; elongation factors splicing; termination factors degrade the protein.
• C. The ribosome's subunits are not needed; initiation factors are not involved; elongation factors terminate translation.
• D. The ribosome catalyzes transcription; initiation factors recruit RNA polymerase; elongation factors remove introns; termination factors polyadenylate.

Answer: (A)

Understanding how the ribosome and its initiation, elongation, and termination factors coordinate to translate mRNA into a protein.

The ribosome, made of small and large subunits, provides the catalytic center for forming peptide bonds, a site created mainly by the large subunit’s rRNA. Initiation factors help assemble the ribosomal subunits with the mRNA and the initiator tRNA at the start codon, establishing the reading frame and readying the complex for elongation. During elongation, elongation factors bring the appropriate aminoacyl-tRNAs to the A site and promote peptide bond formation between the growing polypeptide and the new amino acid; another factor facilitates translocation, moving the ribosome one codon along the mRNA. When a stop codon appears in the A site, termination factors recognize it and trigger release of the finished polypeptide from the tRNA, effectively ending translation.

Other options misplace these roles: the ribosome isn’t a transporter, initiation factors don’t decap mRNA, elongation isn’t about splicing, and transcription is carried out by RNA polymerase, not the ribosome.