OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

How does pH impact enzyme activity?

1. Increased pH always enhances the reaction rate

2. Extreme pH levels denature enzymes

3. pH has no role in enzyme function

4. Optimal pH is consistent for all enzymes

The correct answer is: Extreme pH levels denature enzymes

The impact of pH on enzyme activity is crucial as enzymes, being proteins, are sensitive to their environment. When pH levels become extremely acidic or alkaline, this can lead to denaturation, which is a structural alteration of the enzyme. Denaturation affects the active site of the enzyme, where substrate binding occurs, making it difficult or impossible for the enzyme to function effectively. Enzymes have specific optimal pH levels at which they exhibit peak activity. Deviating significantly from this optimal pH can disrupt ionic bonds and hydrogen bonds within the enzyme's structure, leading to the loss of its three-dimensional shape and resulting in reduced catalytic activity or complete inactivity. This highlights the importance of maintaining an appropriate pH for enzymes to function correctly. Understanding that extreme pH levels can lead to denaturation helps clarify how environmental factors influence biochemical reactions and the specific conditions necessary for enzymes to catalyze reactions efficiently.