Why does a change in pH usually produce a change in the ability of an enzyme to act as a catalyst?
A. When the pH changes, the enzyme may lose its native conformation and lose its ability to function as a catalyst.
B. When the pH changes, enzymes are surrounded by a solvation shell that prevents them from interacting with substrates.
C. When the pH changes, the substrates are protonated and no longer bind to the binding site.
D. When the pH changes, the binding sites of enzymes interact with additional protons causing a localized positive charge that repels the substrate.
The correct answer is A. when the pH changes, the enzyme may lose its native conformation and lose its ability to function as a catalyst.
Explanation:
Enzymes are proteins with a specific three-dimensional structure that allows them to catalyze biochemical reactions. This structure is often referred to as the enzyme's native conformation. The native conformation is crucial for the enzyme's activity because it determines the shape of the active site, where the enzyme binds to its substrate.
pH is a measure of the acidity or alkalinity of a solution. It is known that enzymes have an optimal pH at which they function most efficiently. The reason for this is that changes in pH can disrupt the electrostatic interactions within the enzyme molecule, including ionic and hydrogen bonds, which are crucial for stabilizing the enzyme's three-dimensional structure.
When the pH deviates from the optimal range, the enzyme can undergo conformational changes, leading to a loss of its native structure. This loss of conformation can result in the disruption or distortion of the active site, preventing the enzyme from effectively binding to its substrate. Consequently, the enzyme's catalytic activity decreases or even ceases altogether, leading to a change in its ability to act as a catalyst. Therefore, option A correctly explains why a change in pH usually produces a change in the ability of an enzyme to act as a catalyst.