Which RNA type forms the structural component of ribosomes?

• A. mRNA
• B. rRNA
• C. tRNA
• D. microRNA

Answer: (B)

Ribosomes are built from RNA and proteins, with the structural scaffolding and catalytic core provided by ribosomal RNA. The rRNA molecules fold to form the two ribosomal subunits and create the peptidyl transferase center that catalyzes peptide bond formation, acting as a ribozyme. Messenger RNA carries the genetic code from DNA to the ribosome and guides protein synthesis, but does not contribute to the ribosome’s structure. Transfer RNA delivers amino acids during translation and helps decode codons, yet it is not a component of the ribosome’s architecture. MicroRNA regulates gene expression and has no role in ribosome structure. Therefore, the RNA that forms the structural component of ribosomes is ribosomal RNA.