JEE Main · 2026 · 21 Jan 2026 · Shift 2 · Biomolecules

Enzymes open an alternative pathway of far lower activation energy than the acid-catalysed route, so the enzyme-catalysed hydrolysis of sucrose has the lower activation energy and the first statement is correct. Denaturation disrupts the hydrogen bonds and other weak interactions that hold the secondary and tertiary structures, while the covalent peptide backbone defining the primary structure survives, so the second statement is correct. Nucleotides are linked through phosphodiester bonds between the 3' and 5' carbons of successive sugar units, not by a glycosidic ${\mathrm{C}}_1$-${\mathrm{C}}_4$ link, so the third statement is wrong. The overall folding of a single polypeptide chain is its tertiary structure, while the quaternary structure describes how several chains assemble, so the fourth statement is wrong. Only the first two statements are correct.