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

• 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

TEMPERATUREpH

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