Study Notes
Enzyme action is influenced by various factors including temperature, pH, enzyme and substrate concentrations, inhibitors, and the Michaelis-Menten constant. Immobilizing enzymes offers benefits such as reusability and stability.
- Temperature — The speed of enzyme reactions increases with temperature until the enzyme denatures. Example: Human enzymes work fastest at about 40°C.
- pH — Affects enzyme structure by altering ionic interactions. Example: Changes in pH can alter the active site.
- Enzyme concentration — More enzymes increase reaction rate until substrate becomes limiting. Example: Adding more enzymes speeds up reactions if substrate is available.
- Substrate concentration — Increases reaction rate until active sites are saturated. Example: At saturation, increasing substrate doesn't increase rate.
- Inhibitors — Molecules that reduce enzyme activity by binding to the enzyme. Example: Competitive inhibitors bind to the active site.
- Vmax & Michaelis-Menten Constant — Vmax is the maximum reaction rate; Km indicates enzyme affinity for substrate. Example: Low Km means high affinity.
- Immobilizing Enzymes — Enzymes attached to a solid support for stability and reusability. Example: Lactase immobilized in alginate beads for lactose-free milk.
Exam Tips
Key Definitions to Remember
- Optimum temperature: The temperature at which an enzyme works fastest.
- Denaturation: Loss of enzyme structure and function due to high temperature or extreme pH.
- Vmax: Maximum rate of an enzyme-catalyzed reaction.
- Km: Substrate concentration at which the reaction rate is half of Vmax.
Common Confusions
- Confusing competitive and non-competitive inhibitors.
- Assuming increasing substrate concentration always increases reaction rate.
Typical Exam Questions
- What happens to enzyme activity at high temperatures? Enzymes denature and lose activity.
- How does pH affect enzyme activity? It alters the enzyme's structure and active site.
- What is the effect of increasing enzyme concentration? Increases reaction rate until substrate is limiting.
What Examiners Usually Test
- Understanding of how temperature and pH affect enzyme activity.
- Differences between competitive and non-competitive inhibition.
- Interpretation of graphs showing enzyme activity.