What is the effect of temperature on enzyme activity?

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Temperature affects enzyme activity by changing both how often the enzyme and substrate collide and how stable the enzyme’s shape is. As temperature rises, molecular motion increases, so collisions between substrate and active site happen more frequently and the reaction rate goes up—until the enzyme reaches its optimum temperature. Beyond that, heat starts to disrupt the weak bonds holding the enzyme in its proper shape, changing or destroying the active site and causing denaturation. When denaturation occurs, the enzyme can no longer catalyze the reaction efficiently, so activity drops. So the typical pattern is that activity increases with temperature up to a maximum, then decreases as denaturation sets in. It’s not correct to say there’s no effect or that enzymes always denature with temperature, since many enzymes have a functional temperature range and only denature at sufficiently high temperatures or with extended exposure.