CUET Preparation Today
Identify the incorrect statement with reference to biomolecules. |
In a β-pleated sheet structure, all peptide chains are stretched out to maximum extension and then laid side by side, which are held together by inter-molecular hydrogen bonding. In fibrous proteins, the parallel polypeptide chains are held together by hydrogen and disulphide bonds. Enzymes can catalyze any biochemical reactions. Deficiency of vitamin K increases the blood clotting time. |
Enzymes can catalyze any biochemical reactions. |
The correct answer is Option (3) → Enzymes can catalyze any biochemical reactions. Biomolecules such as proteins, enzymes, and vitamins perform highly specific biological functions. Enzymes are biological catalysts that accelerate biochemical reactions in living organisms. However, enzymes are highly specific in their action. Each enzyme catalyzes only a particular reaction or a group of closely related reactions due to the specificity of the enzyme’s active site. This specificity arises from the lock-and-key model or induced fit model, where only a specific substrate can bind to the enzyme active site. Therefore, enzymes cannot catalyze any biochemical reaction, but only specific reactions for which they are designed. Thus, statement C is incorrect. Option 1 The β-pleated sheet is a secondary structure of proteins in which the polypeptide chains are fully extended and arranged side by side. These chains are stabilized by intermolecular hydrogen bonds between the peptide groups. Therefore, this statement is correct Option 2 Fibrous proteins such as keratin contain parallel polypeptide chains that are stabilized by hydrogen bonds and disulphide linkages. These bonds provide high mechanical strength and structural stability. Therefore, this statement is correct. Option 3 Enzymes exhibit high substrate specificity and catalyze only specific biochemical reactions. They cannot catalyze all biochemical reactions. Therefore, this statement is incorrect. Option 4 Vitamin K is essential for the synthesis of prothrombin and other clotting factors required for blood coagulation. Deficiency of vitamin K results in delayed blood clotting and increased clotting time. Therefore, this statement is correct.
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