BitWithBite
MDCAT Prep · Biology · Quick Reference
Lesson 4 — Enzymes Cheat Sheet
In one line: Competitive inhibitors fight for the active site (Km↑, Vmax same); non-competitive inhibitors bind elsewhere (Vmax↓, Km same).
Key Ideas
1What enzymes do. Protein catalysts that lower activation energy, are substrate-specific, and aren't consumed.
2Vmax & Km. Vmax = max velocity. Km = [S] at half Vmax. Low Km = high affinity.
3Competitive inhibition. Binds active site; more substrate overcomes it; Vmax unchanged, Km increases.
4Non-competitive inhibition. Binds allosteric site; more substrate can't overcome it; Vmax decreases, Km unchanged.
5Temperature. Human enzymes peak around 37°C; too hot denatures them.
pH Optima
Pepsin (stomach)
pH 2
Amylase (saliva)
pH 7
Trypsin (small intestine)
pH 8
Competitive: Vmax same, Km ↑
Non-competitive: Vmax ↓, Km same