Enzymes

What are they

Proteins that function as a biological catalyst

Characteristics

Speed up rate chemical reactions (Digestion of food molecules)

High specific

Remain chemically unchanged after reaction

Required in minute amounts

One type of enzyme can only catalyse one type of reaction

Can be reused

Affected by temperature and pH

Denaturation: Active site of an enzyme irreversibly changes shape and the substrate can no longer fit to the active site of the enzyme

Enzymes are made of protein and will denature at high temperature and extreme change in pH

Lock and Key Hypothesis

E.g. Starch (Substrate) and Amylase (Enzyme)

Only starch can bind complementarily to the active site of amylase

Enzyme-Substrate complex is formed

Starch (Substrate) acts as the 'Key'

Starch (Substrate) forms maltose(Product) which leaves the active site of amylase

Amylase (Enzyme) acts as the 'Lock'

Amylase(Enzyme) remains unchanged and can be reused again

Effect of temperature on enzyme activity

As temperature increases

At optimum temperature

At low temperature

Above optimum temperature

Enzyme is less active/inactive

Reaction is slow/ No reaction

Enzyme and substrate possess more kinetic energy and move faster

Enzyme is most active

Enzymes gradually denature

Enzyme activity and speed of reaction increases

For every 10°C increase, rate of reaction doubles

Rate of reaction is highest

Substrate cannot bind complementarily to active site of enzyme

At high temperatures, enzymes are completely denatured

Reaction stops

Effect of pH on enzyme activity

At optimum pH

As pH increases/decreases from optimum pH

Enzyme is most active

Rate of reaction is highest

Enzymes are gradually denatured

Substrate cannot bind complementarily to active site of enzyme

At pH levels very far from the optimum pH, the enzymes are full denatured

Reaction eventually stops

Different enzymes work at different ranges of pH, extreme changes of pH denature the enzyme

Salivary amylase in mouth (pH 7)

Pancreatic enzymes in small intestine (pH 9)

Pepsin in Stomach (pH 1-2)