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Enzymes
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Summary Notes
A catalyst is a chemical that speeds up the rate of a reaction.
A catalyst is a chemical that speeds up the rate of a reaction yet remains
unchanged itself.
Enzymes are biological catalysts, made of protein, that speed up chemical
reactions inside a cell.
The substance upon which an enzyme acts on is called a substrate. The
substance(s) that are produced following an enzyme reaction are called products.
Each enzyme is specific as it acts on only one type of substrate.
These are some examples of enzymes and their substrates and products.
 Amylase breaks down starch to maltose.
 Pepsin breaks down protein to amino acids.
 Lipase breaks down fat to fatty acids and glycerol.
Lock and Key Theory
Substrate
Products
Active Site
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Enzyme
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Enzyme
Optimum is the condition at which enzyme activity works best. Each enzyme has
an optimum temperature and an optimum pH.
These are some examples of enzymes and their optimum pH.
 The optimum pH for pepsin is pH 2.5. The range of pH at which pepsin is
active is pH 1 to pH 4.5.
 The optimum pH for catalase is pH 9. The range of pH at which catalase is
active is pH 6 to pH 12.
As temperature increases
enzymes activity increases
until an optimum
temperature is reached.
After this point, as
temperature increases,
enzyme activity decreases
until the enzyme is
denatured.
The enzyme amylase has an optimum temperature of 37˚C.
When an enzyme is denatured the shape of its active site has been altered. The
substrate and enzyme are unable to react.
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Enzymes are used for many commercial applications such as; biological detergents
and clarifying apple juice.