Which factor decreases enzymatic speed when conditions become extreme?

Which factor decreases enzymatic speed when conditions become extreme?

• A. pH
• B. Substrate concentration
• C. Temperature beyond a certain point
• D. Rising temperature

Answer: (C)

Enzymes have an optimum temperature at which they function best. As temperature rises, molecular collisions between enzymes and substrates occur more frequently, so the reaction rate increases up to that optimum. Beyond that point, the heat disrupts the enzyme’s delicate three-dimensional structure, breaking hydrogen bonds and other interactions that maintain the active site's shape. When the active site is distorted, substrates no longer bind properly, and catalysis slows or stops. That is why the statement describing a temperature beyond a certain point best explains the decrease in enzymatic speed under extreme conditions. The other factors don’t fit the same way here. Substrate concentration boosts rate only until enzymes become saturated, not because extreme conditions reduce speed. A general rise in temperature tends to increase speed up to the optimum, rather than immediately decreasing it. While extreme pH can also harm enzymes, the option focusing on exceeding an optimal temperature specifically captures the loss of activity due to denaturation from heat.

Enzymes have an optimum temperature at which they function best. As temperature rises, molecular collisions between enzymes and substrates occur more frequently, so the reaction rate increases up to that optimum. Beyond that point, the heat disrupts the enzyme’s delicate three-dimensional structure, breaking hydrogen bonds and other interactions that maintain the active site's shape. When the active site is distorted, substrates no longer bind properly, and catalysis slows or stops. That is why the statement describing a temperature beyond a certain point best explains the decrease in enzymatic speed under extreme conditions.

The other factors don’t fit the same way here. Substrate concentration boosts rate only until enzymes become saturated, not because extreme conditions reduce speed. A general rise in temperature tends to increase speed up to the optimum, rather than immediately decreasing it. While extreme pH can also harm enzymes, the option focusing on exceeding an optimal temperature specifically captures the loss of activity due to denaturation from heat.