Enzyme Control of Chemical Reactions in Cells

Enzymes are biological catalysts that speed up chemical reactions in cells.
Without enzymes, these reactions would take place too slowly to keep living organisms alive.
Enzymes are not used up in the reactions and can be used over and over again.
Enzymes are made up of proteins and have a specific shape (the active site), which fits onto the substance involved in the reaction (the substrate).
Each type of enzyme is designed to catalyse a specific reaction or type of reaction, meaning they are selective.
Enzymes can work both inside and outside of cells.
The rate of enzyme activity can be affected by temperature, pH levels and substrate concentration.
If the temperature is too high, the enzyme will be denatured, altering its shape and therefore its active site. This prevents the substrate from fitting and the enzyme can no longer function.
If the temperature is too low, the rate of enzyme reaction will be slow because molecules move slower and collide less often.
Enzymes have an optimum pH that they work best at. If the pH is too high or too low, it can denature the enzyme, changing its shape.
Increasing the substrate concentration will increase the rate of enzyme activity, until all the enzymes are occupied – then the rate stays the same.
Inhibitors can slow down or stop enzyme reactions. There are two types: competitive inhibitors (which compete with the substrate for the active site of the enzyme) and non-competitive inhibitors (which attach to the enzyme elsewhere and change its shape making it ineffective).
Enzyme reactions can be represented using lock and key diagrams or induced fit models to visualise the specific interaction between the enzyme and its substrate.
Enzymes have a range of important roles in cells including digestion of nutrients, synthesis of new molecules, and the breakdown of waste products.