Enzyme Active Site & pH

Enzyme Active Site & pH is an interactive 3D biochemistry lab showing how globular enzymes recognise specific substrates and catalyse reactions. Students drag the green substrate molecule into the sculpted active-site cleft to trigger an induced-fit conformational hug that splits the substrate into products. They can also drag a red competitive inhibitor into the active site or a purple non-competitive inhibitor into the side allosteric pocket. Sliders for temperature, solution pH, and substrate concentration update live readouts for reaction rate, active site conformation, percentage of enzyme bound, and effective Vmax.

• Drag the green substrate molecule into the glowing active-site cleft and watch the enzyme jaws close by induced fit before releasing two product lobes.
• Raise Temperature above 46 °C and watch the enzyme jaws unfold as thermal denaturation destroys the active site and drops the reaction rate.
• Select Competitive inhibitor and raise Substrate concentration to 100 mM to see how high substrate levels can outcompete a competitive blocker.
• Select Non-competitive inhibitor to bind the allosteric pocket and observe why adding more substrate cannot restore Vmax.
• Sweep Solution pH from 1 to 14 to find the neutral pH 7 optimum and observe denaturation in strong acid or alkali.

1. 1Explain the induced-fit model of enzyme-substrate catalysis and how enzymes lower activation energy.
2. 2Describe why extreme high temperatures or extreme pH values cause irreversible denaturation of the active site.
3. 3Distinguish between competitive inhibition at the active site and non-competitive inhibition at an allosteric site.
4. 4Predict how substrate concentration affects reaction rate in the presence and absence of inhibitors.

Questions teachers ask