JEE Chemistry 2026 Question with Solution

Given: Four statements about biomolecules, protein structure, denaturation, and nucleotide linkage are to be checked.

Find: Which statements are correct and hence the correct option.

Evaluate Statement A: Enzymes are biological catalysts and lower the activation energy of a reaction more effectively than acid catalysis in sucrose hydrolysis. Therefore, statement A is true.

Evaluate Statement B: During denaturation, the secondary and tertiary structures are disrupted, but the primary structure with peptide bonds remains intact. Therefore, statement B is true.

Evaluate Statement C: Nucleotides in nucleic acids are joined by phosphodiester linkage between the $3'$ carbon of one pentose sugar and the $5'$ carbon of the next. The glycosidic linkage connects the sugar to the nitrogenous base, not one nucleotide to another. Therefore, statement C is false.

Evaluate Statement D: The overall folding of a single polypeptide chain is called the tertiary structure. Quaternary structure refers to the arrangement of multiple polypeptide chains. Therefore, statement D is false.

So, only statements A and B are correct.

The correct option is B.

Given:

• Statement A compares activation energy in enzyme catalysed and acid catalysed hydrolysis of sucrose.
• Statement B concerns denaturation of proteins.
• Statement C concerns linkage between nucleotides.
• Statement D concerns quaternary structure of proteins.

Find: Identify the true statements.

Step 1: Recall that enzymes are highly specific biological catalysts. They lower the activation energy barrier for the reaction they catalyse.

Step 2: In protein denaturation, weak interactions responsible for higher-order folding are disturbed, but peptide bonds are not broken under ordinary denaturation conditions.

Step 3: In nucleic acids, adjacent nucleotides are connected through phosphodiester bonds, specifically involving the $3'$ and $5'$ carbons of pentose sugars.

Step 4: Protein structural levels are:

• Primary structure: sequence of amino acids
• Secondary structure: local folding such as helix or sheet
• Tertiary structure: overall folding of one polypeptide chain
• Quaternary structure: arrangement of multiple polypeptide subunits

From these facts:

• A is true.
• B is true.
• C is false.
• D is false.

Therefore, the correct answer is A and B only, so the correct option is B.