Which of the following catalytic activities is performed by an RNA molecule rather than by a protein enzyme?

• A Hydrolysis of dietary proteins by pancreatic proteases
• B Formation of peptide bonds during translation by the large ribosomal subunit ✓
• C Oxidation of succinate in the citric acid cycle
• D Phosphorylation of glucose by hexokinase

Explanation

The peptidyl transferase activity of the 50S ribosomal subunit resides in the 23S rRNA, making peptide bond formation a ribozyme-catalysed reaction; no ribosomal protein lies near the catalytic site. Catalytic RNAs such as RNase P provide other examples. All remaining options describe classical protein enzymes, so they cannot serve as the key. This fact is frequently tested to illustrate that proteins are not the only biological catalysts.

Reference: Lehninger Principles of Biochemistry, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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