What are the factors
affecting Enzyme
Activity?
Recap
What are enzymes?
• Biological catalysts made up of proteins
Function of Enzymes
• Enzymes speed up the rate of chemical
reactions in the body; both breaking down
(e.g.: starch into maltose)
and building up reactions. (e.g: amino acids
into proteins).
• Enzymes lower the activation energy
required to start a chemical reaction
Characteristics of Enzymes
• Enzymes are highly specific
in action.
• Enzymes remain chemically
unchanged at the end of
the reaction.
• Enzymes are required in
minute amounts.
ase
Protein
Substrate Name +
-ase
Carbohydrate
ase
Mode of Action
Substrate fits in the enzyme active site,
just like a key fits into a lock.
An enzyme-substrate complex is formed.
Chemical reactions occur at the active site and products
are formed.
What are the factors
affecting Enzyme
Activity?
catalase
Hydrogen peroxide  water and oxygen
What affects enzyme activity?
Petri Dish
1
2
Condition of
potato
pieces
Raw
Cooked Frozen
Observations
3
4
5
Soaked
in
Acid
Soaked
in
Alkali
0°C
• Low temperatures  low Kinetic Energy
of enzymes and substrates.
• No/Very few enzyme-substrate
complexes are formed.
• Enzymes are inactivated.
20°C (increasing temperature)
• Increasing the temperature will lead to the increase
in kinetic energy of enzyme and substrate molecules.
• Enzyme and substrate molecules move with
increasing speed and collide more frequently with
each other.
• This increases the rate of enzyme-substrate complex
formation This increases the rate of enzymesubstrate complex formation and product
formation.
Rate of reaction increases
37°C
• As the temperature continues to
increase, the rate of enzyme activity also
increases until the optimal temperature
is reached.
• Optimal temperature is the temperature
at which the enzyme works best. Rate of
product formation is highest!
Beyond Optimal Temperatures
• At high temperatures (>60°C), weak bonds
within the enzyme molecule are broken
• Enzyme loses its shape and its active site.
• Loss of shape leads to a loss of function.
Enzyme is said to have denatured
• Denaturation is the change in 3D structure of
an enzyme or any other protein caused by
heat or chemicals such as acids or alkali,
causing it to lose its function.
Denaturation
Different enzymes denature at different temperatures. Most enzymes denature at
temperatures higher than 60°C. However, there are some enzymes that stay active even
at high temperatures like 80°C (Enzymes in the bacteria Thermus aquaticus)
Effect of pH on enzyme activity
• Enzyme works best within a narrow pH
range
• Each enzyme works best at particular pH,
known as its optimum pH level.
• At extreme pH levels, enzymes lose their
shape and function and become
denatured.
Effect of pH on enzyme activity
Effect of Substrate on Enzyme Activity