Effect of changes in temperature on enzyme activity:
- Low temperature:
  - When temperature is too low, the enzyme action becomes ineffective.
  - At low temperature, energy is insufficient for the enzymes to collide with substrates. The reaction will then become very slow.
  - To bind with substrates, enzymes require kinetic energy, also known as movement energy.
  - Kinetic energy is needed for the enzyme and the substrate to collide with each other and form the enzyme-substrate complex.
  - When the temperature is low, the kinetic energy is low, and the enzyme is less active.
  - As temperature increases, the kinetic energy increases.
  - When the enzymes move faster, the frequency of effective collisions between enzymes and substrates will also increase.
  - Therefore the rate of formation of the enzyme-substrate complex increases.
  - This leads to an increase in the formation of the products.
- Optimum temperature:
  - Different enzymes have different optimum temperatures.
  - This is the temperature at which the enzyme is most active.
  - An enzyme reaches its maximum rate of reaction at its optimum temperature.
  - The enzyme activity starts to decrease if the temperature is increased beyond the optimum temperature.
- High temperature:
  - Enzymes are mostly protein molecules. When exposed to high temperatures that exceed the functioning temperature of the enzyme, they become denatured.
  - Denaturation is the change in the structure of an enzyme, which leads to deformation of the shape of the active site of the enzyme.
  - Since the active site loses its important shape, the enzyme and the substrate are no longer complementary to each other.
  - The enzyme can no longer bind with the substrate and hence the enzyme-substrate complex will not be formed.
  - Without enzyme-substrate complexes, reactions cannot proceed, and products will not be produced.
  - Hence, enzyme-substrate reactions will not proceed if the temperature is too high or too low.
    - For example, human enzymes work best at a body temperature or about 37°C. Anything too high can cause the enzymes to denature.
    - This is why high fever above 40°C can be life threatening. Our body functions are severely affected due to the denaturation of enzymes.

Effect of changes in pH on enzyme activity:
- Another factor that can cause the denaturation of enzymes is pH.
- pH is a scale used in chemistry to measure how acidic or basic a solution is.
- Changes in pH can denature enzymes and can alter the shape and function of enzymes, and thus change the structure of the active site.
- Similar to temperature, enzymes have an optimum pH value as well. This can be shown by a graph on the effect of pH on enzyme activity.
- At pH 7 the enzyme is most active.
- When the pH is lower or higher than 7, enzyme activity starts to decrease.
- Different enzymes have different optimum pH values.
- In the graph, at pH below 5 and pH above 9.5, there is no enzymatic activity.
- When enzymes are not in their optimum states, the rate of reaction will decrease.
- The following graph shows the optimal pH values for some of the enzymes present in our digestive system.

5.02 - Enzymes (II)

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