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)