Factors Affecting Enzyme Activity - Practice Questions & MCQ

Factors Affecting Enzyme Activity

1. Substrate Concentration and Km: 

• Generally, enzyme activity increases as substrate concentration increases because there are more collisions between substrate molecules and the enzyme.
• As more substrate molecules fill active sites, more product results per unit time.
• But when the active sites are filled almost continuously with substrate, the rate of the reaction cannot increase any more. Maximum rate has been reached.
• Michaelis Menten Constant, Km describes the substrate concentration that is needed to achieve a reaction that is exactly half the maximum velocity of the reaction.
• For example, the Km is decreased when the competitive inhibitor is present.

2. Optimal pH:

• Each enzyme has an optimal pH at which the rate of the reaction is highest.
• At this pH value, these enzymes have their normal configurations.
• A change in pH can alter the ionization of the side chains and disrupt normal interactions, and under extreme conditions of pH, the enzyme becomes inactive.

3. Optimal Temperature:

• Typically, as the temperature rises, enzyme activity increases because warmer temperatures cause more effective collisions between enzyme and substrate.
• If the temperature rises beyond a certain point, enzyme activity eventually levels out and then declines rapidly because the enzyme is denatured.
• An enzyme’s shape changes during denaturation, and then it can no longer bind its substrate(s) efficiently

4. Protein poisons:

• Cyanides, azides, iodoacetate, and salts of heavy metals destroy tertiary structure of enzymes by either combining with cofactor or a group of apoenzyme (- SH group, -COOH).