Enzymes Enzymes are proteins Enzymes are biological catalysts They increase the rate of reactions Ex. photosynthesis, respiration, protein synthesis Each enzyme is specific to a substrate Substrates are changed into products Enzymes are not used up in a reaction – they can be used over and over again

The “lock and key” theory Each enzyme has a different shape Within the shape is the active site Only one type of substrate fits into the active site (like a lock and key)

The “lock and key” theory The enzyme is the “lock” The substrate is the “key”

The “lock and key” theory Once the substrate is attached to the active site it is turned into the 2 products

Denaturing enzymes TEMPERATURE pH Enzymes can be denatured If the shape of enzyme changes, the substrate cannot fit into the active site Two factors can cause enzymes to be denatured TEMPERATURE pH

How? Temperature As temperature increases, so does the rate of reaction. But only up to a certain point as the enzyme becomes denatured at too high temperatures. At 40°C the enzyme works at its optimum

How? pH Different enzymes work best at different pH values. The optimum pH value depends on the enzymes and where it works. This enzymes optimum is pH8. But enzymes become denatured at pH values too far from their optimum. Enzymes in the stomach have an optimum pH of 2