Chapter 4: Enzymes

Enzymes

Are biological catalysts made of proteins. They alter the rate of chemical reactions without being chemically changed at the end of reaction and are specific nature.

Enzyme-Catalysed Reaction:

• Amylase digests starch.

• Cellulase digests cellulose (only in plants not in humans).

• Protease digests proteins.

• Lipase digests fats.

Characteristics of Enzymes:

• Speed up chemical reactions.

• Required in minute amounts.

• Are specific.

Factors affecting Enzyme Activity:

• pH: they work best at optimum pH. As pH moves away from the pH scale the rate of reaction decreases. A change in pH causes the shape of active site to change.

• Temperature: works best at optimum temperature. At a temperature above optimum temperature the enzyme denatures.

• Enzyme and Substrate concentration: as the substrate concentration increases the rate of reaction increases to an initial point to make reaction constant + Increase in enzyme concentration increases rate of enzyme reaction.

Lock and Key hypothesis: