Unit 3 · Cellular energetics
Enzyme kinetics lab
Adjust substrate concentration, temperature, pH, and inhibitors, and watch how each one reshapes the reaction-rate curve.
Reaction conditions
Change one variable at a time to see what it actually controls.
Substrate binding, in action
Click “Run reaction” to watch one substrate molecule dock into the active site and undergo a catabolic reaction — breaking down into two smaller products.
Reaction rate vs. substrate concentration
This is the curve every setting above is reshaping — the amber dot marks the current [S] and rate.
The curve rises steeply at low [S], then bends toward a ceiling (Vmax) as the enzyme's active sites become saturated — adding more substrate stops helping once nearly every enzyme is already busy.
Km is where the curve crosses half of Vmax. A competitive inhibitor drags the whole curve rightward (same ceiling, more substrate needed to get there); a noncompetitive inhibitor pulls the ceiling down without moving Km.
What each variable is actually doing
Same equation, four different knobs.
Competitive inhibitor
Blocks the entrance to the active site, so it takes more substrate to reach the same rate — Km goes up. Enough substrate can still out-compete the inhibitor, so Vmax is unchanged.
Noncompetitive inhibitor
Binds somewhere other than the active site and disables the enzyme regardless of substrate — Vmax drops. Adding more substrate can't fix it, so Km stays the same.