Unit One‎ > ‎


Enzymes are biological catalysts, this is a substance that increases the rate of a chemical reaction by lowering the amount of energy needed to make the reaction occur. Without these biological catalysts, biochemical pathways such as respiration would occur much slower.

Enzymes are made of protein, they are said to be specific to their substrate and also work through a lock and key mechanism.

Here's a little YouTube clip to help you understand everything about enzymes:

Enzyme Action

Factors Affecting Enzyme Action

many different things can affect the rate of the reaction of an enzyme, these include: Temperature, pH, enzyme concentration and substrate concentration.

A high temperature causes the denaturation of the enzyme, causing the reaction to slow down and eventually stop. Enzymes work in an optimum pH (usually 7 - neutral), however there are exceptions. If an enzyme is in it's optimum temperature then it will be able to work at a muchfaster rate than if it was in an unsuitable pH. If enzyme concentration is high then the reaction rate will be high (as long as there is                                                                    an adequate supply of substrate), whereas if the substrate concentration is high then the                                         reaction rate will be high.


  • Non-competitive - these attach to the side of the enzyme and denature their active site, rendering them useless.
  • Competitive - These compete with the substrate for the active site of the enzyme, the reaction rate continues at the same speed but quickly stops as all of the active sites have been used up.
Here is a simple graph to show the effects of inhibitors: