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

What happens to enzymes if body temperature falls outside the ideal range?

1. They become more efficient

2. They denature

3. They multiply

4. They remain unchanged

The correct answer is: They denature

Enzymes are proteins that act as catalysts in biological reactions, meaning they accelerate chemical reactions necessary for life. Each enzyme operates optimally within a specific temperature range, usually around the body’s normal temperature (approximately 37 degrees Celsius in humans). When body temperature drifts outside this ideal range, particularly when it decreases, enzymes can undergo denaturation. Denaturation refers to the structural changes that occur in enzymes as a result of temperature fluctuations. When the temperature drops, the molecular movement slows down, causing the enzyme's three-dimensional shape to change; this disrupts the active site, where substrate molecules bind. If the active site is altered, the enzyme can no longer effectively bind to its substrate or catalyze reactions. This results in a significant reduction in enzymatic activity, which can impede metabolic processes and overall cellular function. In contrast, if body temperature were to rise above optimal levels, a similar denaturing effect can occur. However, the key focus here is on the effect of lowering temperature, which solidifies the understanding that enzymes are sensitive to temperature changes and can lose their functionality when those changes are outside the ideal range. Thus, denaturation is the most accurate consequence when body temperature falls significantly outside the optimal conditions.