Discuss the factors affecting enzyme activity.

1. 1 · Open in two lines. The rate (velocity) of an enzyme reaction depends on several factors. Each is studied by changing one factor while keeping the others constant.
2. 2 · Draw the graphs. [Graphs: hyperbola for substrate with Vmax and Km marked; straight line for enzyme; bell-shaped curves for temperature and pH]
3. 3 · Substrate and enzyme concentration.
   • Substrate: rate rises, then levels off at Vmax. Km = substrate level at ½ Vmax.
   • Enzyme: rate rises in direct proportion when substrate is in excess.
4. 4 · Temperature and pH.
   • Temperature: optimum about 37 °C; high heat denatures the enzyme.
   • pH: each enzyme has its own optimum (pepsin about 2, trypsin about 8).
5. 5 · Activators, product and inhibitors.
   • Activators: Cl− (salivary amylase), Mg2+ (kinases).
   • Product build-up slows the reaction.
   • Competitive: malonate, statins. Non-competitive: lead. Irreversible: organophosphates, aspirin.
6. 6 · Significance. Explains how many drugs and poisons act, and why high fever harms the body.
7. 7 · Nutrition link. Blanching, refrigeration and acid preserve food by controlling enzymes; minerals act as activators.
8. 8 · Close in one line. Enzyme activity is fine-tuned by its surroundings, which both the body and food scientists control.

Scoring tip: Small labelled graphs beat long text here. Mark Km and Vmax on the substrate curve.