B2 - Enzymes

What are enzymes?

Biological catalysts, they speed up useful chemical reactions in the body.

What is a catalyst?

A substance which increases the speed of reaction without being changed or used up in the reaction.

What is the ‘lock and key’ model of enzymes?

The active site of the enzyme has a unique shape that fits onto the substance involved in the reaction. The substrate slots onto the enzyme’s active site and catalyses the reaction where the substrate either breaks apart or joins together. The enzyme is unchanged after the reaction.

What two factors affect the rate of enzyme-catalysed reactions?

Temperature and pH.

What happens the rate of enzyme reaction as temperature increases?

It increases at first then reaches the optimum temperature then the enzyme becomes denatured if it is too hot and decreases quickly.

How does pH affect enzyme reaction activity?

If the pH is too high or low, the active site of enzymes become denatured, they have an optimum pH which is often 7 but not always.