Question

Which of the following exhibit catalytic function

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

Hint:

The peptide bond formation step during translation is catalyzed directly by rRNA acting as a ribozyme inside the active site of the ribosome.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Most biological catalysts are proteins (enzymes), but certain RNA molecules can also act as catalysts.
These catalytic RNA molecules are referred to as ribozymes.

Step 2: Detailed Explanation:
Let us analyze the functions of the different RNA classes listed in the options:
- Messenger RNA (mRNA) (A) serves as a template that carries genetic information from DNA to the ribosome for translation, but it lacks catalytic activity.
- Transfer RNA (tRNA) (C) acts as an adapter molecule that delivers specific amino acids to the ribosome, matching codons with anticodons, but it does not perform catalysis.
- Small interfering RNA (siRNA) (D) is involved in the RNA interference pathway to guide protein complexes to target complementary mRNA molecules, but it does not carry out catalytic cleavage itself.
- Ribosomal RNA (rRNA) (B) is a major structural and functional component of ribosomes.
Crucially, peptidyl transferase activity—the enzymatic reaction that forms peptide bonds between amino acids during translation—is catalyzed directly by the 23S rRNA in prokaryotes and the 28S rRNA in eukaryotes.
The active site of the ribosome is composed entirely of RNA, demonstrating that the ribosome is a ribozyme.
Therefore, ribosomal RNA exhibits catalytic function.

Step 3: Final Answer:
The correct option is (B).