Heat an enzyme to 60 °C, then cool it. Does it work again?

1 Predict

An enzyme that works best at 37 °C is heated to 60 °C, then cooled back to 37 °C. Does it work again?

2 Test it

Drag the temperature down to the cold, back up, then past 50 °C, then cool it again.

3 Why

Answer: No, it stays denatured

Cold only slows an enzyme down: its molecules move less, but its shape is intact, so it works again when warmed.

Heat breaks the hydrogen and ionic bonds that hold the enzyme’s shape. The active site changes, the substrate no longer fits, and cooling does not restore it: the enzyme is denatured for good.