The correct statements are :
A. Activation energy for enzyme catalysed hydrolysis of sucrose is lower than that of acid catalysed hydrolysis.
B. During denaturation, secondary and tertiary structures of a protein are destroyed but primary structure remains intact.
C. Nucleotides are joined together by glycosidic linkage between \( C_1 \) and \( C_4 \) carbons of the pentose sugar.
D. Quaternary structure of proteins represents overall folding of the polypeptide chain.
Choose the correct answer from the options given below :
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Remember: Primary structure = sequence of amino acids (peptide bonds); Tertiary structure = 3D shape of one chain; Quaternary = interaction between multiple chains.
Step 1: Understanding the Concept:
Biomolecules like proteins, enzymes, and nucleic acids have specific structural features and catalytic mechanisms.
Step 3: Detailed Explanation: Statement A: Enzymes are biological catalysts. They lower the activation energy of a reaction much more efficiently than inorganic catalysts (like \( H^+ \) in acid catalysis). For sucrose hydrolysis, the enzyme sucrase significantly reduces the barrier compared to mineral acids. This is true. Statement B: Denaturation occurs when proteins are subjected to heat or pH changes. It involves the disruption of hydrogen bonds and disulfide bridges that stabilize secondary and tertiary structures. The strong covalent peptide bonds that form the primary structure remain unaffected. This is true. Statement C: Nucleotides in a strand of DNA or RNA are joined by phosphodiester linkages between the \( 3' \) carbon of one sugar and the \( 5' \) carbon of the next. Glycosidic linkages connect the sugar to the nitrogenous base. This is false. Statement D: The overall folding of a \textit{single} polypeptide chain is the tertiary structure. Quaternary structure refers to the spatial arrangement of multiple polypeptide chains (subunits). This is false.
Step 4: Final Answer:
Statements A and B are correct.
