Question

The correct statements are:

• Activation energy for enzyme catalysed hydrolysis of sucrose is lower than that of acid catalysed hydrolysis.
• During denaturation, secondary and tertiary structures of a protein are destroyed but primary structure remains intact.
• Nucleotides are joined together by glycosidic linkage between \( C_1 \) and \( C_4 \) carbons of the pentose sugar.
• Quaternary structure of proteins represents overall folding of the polypeptide chain.

• A. A, C and D Only
• B. A, B and D Only
• C. A and B Only
• D. B and C Only

Hint:

Important facts:

• Enzymes decrease activation energy.
• Denaturation does not break peptide bonds.
• DNA nucleotides are linked by phosphodiester linkage.
• Tertiary structure represents overall folding of a chain.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
This question deals with the core biochemical principles governing biomolecules. It evaluates the thermodynamic mechanisms of enzyme catalysis, the structural stability of protein architectures under denaturing stresses, and the specific covalent connectivity of nucleic acids.
Step 2: Detailed Explanation:
Let us analyze each statement individually to check its scientific accuracy: - Statement A: Enzymes are highly specific biocatalysts that accelerate chemical reactions by creating a preferred alternate pathway with a dramatically lower activation energy ($E_a$) barrier. For instance, the acid-catalyzed hydrolysis of sucrose requires an activation energy of about $62 \text{ kJ mol}^{-1}$, whereas the enzyme sucrase drops this barrier to approximately $29 \text{ kJ mol}^{-1}$. Thus, Statement A is correct. - Statement B: Denaturation happens when a protein is subjected to physical or chemical changes (like extreme heat, shifts in pH, or detergents). This disrupts the weak hydrogen bonds, hydrophobic interactions, and disulfide bridges holding the folded form together. Consequently, the secondary, tertiary, and quaternary structures unravel. However, the strong, covalent peptide bonds that construct the primary amino acid sequence are not cleaved and remain fully intact. Thus, Statement B is correct. - Statement C: Within nucleic acids, individual nucleotides are linked together linearly by a phosphodiester linkage connecting the C3' carbon of one pentose sugar to the C5' carbon of the adjacent pentose sugar. Glycosidic linkages instead join the nitrogenous base to the C1' position of the pentose sugar. Thus, Statement C is incorrect. - Statement D: The overall folding, looping, and compact packing of a solitary polypeptide chain into a distinct three-dimensional shape represents its tertiary structure. Quaternary structure specifically refers to the spatial arrangement and interaction of multiple individual polypeptide subunits relative to one another. Thus, Statement D is incorrect. Reviewing the analysis, only statements A and B are correct, which corresponds to option (C).
Step 3: Final Answer:
The correct statements are A and B Only.