Which of the following statements about enzymes is INCORRECT? MCQ with Answer and Explanation

Which of the following statements about enzymes is INCORRECT?
A. Enzymes are proteins
B. Enzymes lower the activation energy of a reaction
C. Enzymes work optimally at high temperatures (>100°C)
D. Enzymes are highly specific in action
Answer: Option C
Solution (By JKExamLibrary)
Enzymes are biological catalysts that function optimally at moderate temperatures (around 35-40°C for human enzymes). Most enzymes denature and lose activity at temperatures above 50-60°C, as the protein structure unfolds. They are highly specific (lock-and-key model), protein in nature, and lower activation energy without being consumed. Some thermophilic bacteria have enzymes active at high temperatures, but typical enzymes are not stable at >100°C.

Discuss this Question (0)

No comments yet. Be the first to start the discussion!

Practice More chemistry Questions

Question #1
Corrosion of iron is an electrochemical process that requires:
A. Only CO₂
B. An electrolyte, oxygen, and water
C. Only nitrogen
D. Only high temperature

Correct Answer: Option B


Explanation:
Rusting involves anodic oxidation of iron (Fe → Fe²⁺ + 2e⁻) and cathodic reduction of oxygen (O₂ + 2H₂O + 4e⁻ → 4OH⁻) in the presence of water acting as electrolyte. CO₂ can form carbonic acid accelerating it, but not required. Nitrogen is inert. High temperature alone doesn't cause rusting without moisture and oxygen.

This question belongs to: Science chemistry
Question #2
The formation of ammonium ion (NH₄⁺) from NH₃ and H⁺ involves:
A. Coordinate bond
B. Metallic bond
C. Ionic bond
D. Covalent bond

Correct Answer: Option A


Explanation:
NH₃ has a lone pair on nitrogen; it donates this pair to H⁺ to form a coordinate (dative) bond, where both electrons in the bond come from nitrogen. The resulting NH₄⁺ has four equivalent N-H bonds.

This question belongs to: Science chemistry
Question #3
Which of the following increases the rate of a chemical reaction?
A. Using larger pieces of solid reactants
B. Adding a positive catalyst
C. Decreasing concentration of reactants
D. Decreasing temperature

Correct Answer: Option B


Explanation:
A positive catalyst increases reaction rate by lowering activation energy. Decreasing temperature generally slows reactions. Decreasing concentration reduces collision frequency, lowering rate. Larger pieces have less surface area, slower reaction. Other rate-increasing factors: increasing temperature, increasing pressure (for gases), using finely powdered solids, and light for photochemical reactions.

This question belongs to: Science chemistry