Which statement is true about enzymes?

Which statement is true about enzymes?

• A. They are part of the product
• B. They are used up in the reaction
• C. Their activity can be affected by temperature and pH
• D. They slow down the rate of the reaction

Answer: (C)

Enzymes are biological catalysts that speed up reactions by lowering the activation energy, and they aren’t consumed or built into the products—after a reaction, they’re free to catalyze more. The statement that their activity can be affected by temperature and pH is true because enzymes depend on their environment: at an optimal temperature, reactions proceed quickly, but if the temperature is too high, the enzyme can denature and lose its shape, especially around the active site. Acidic or basic conditions (pH) also disrupt the ionization of amino acid residues and the overall structure, reducing or stopping activity outside the optimal range. The other ideas don’t fit because enzymes aren’t part of the product, aren’t used up in the reaction, and, under proper conditions, they accelerate rather than slow down the reaction.

Enzymes are biological catalysts that speed up reactions by lowering the activation energy, and they aren’t consumed or built into the products—after a reaction, they’re free to catalyze more. The statement that their activity can be affected by temperature and pH is true because enzymes depend on their environment: at an optimal temperature, reactions proceed quickly, but if the temperature is too high, the enzyme can denature and lose its shape, especially around the active site. Acidic or basic conditions (pH) also disrupt the ionization of amino acid residues and the overall structure, reducing or stopping activity outside the optimal range. The other ideas don’t fit because enzymes aren’t part of the product, aren’t used up in the reaction, and, under proper conditions, they accelerate rather than slow down the reaction.