Review and update history
Last reviewed on June 3, 2026. Time-sensitive claims are checked against official sources when this page is materially updated.
Enzyme kinetics is not a graph-memorization topic. The MCAT uses Km, Vmax, inhibitors, and Lineweaver-Burk plots to ask what changed about binding, catalysis, or both.
The two-question method
For every kinetics passage, ask:
- Did substrate binding change?
- Did maximum catalytic output change?
If only apparent Km changes, think about affinity or substrate competition. If Vmax changes, think about active enzyme amount, catalytic capacity, or inhibitors that cannot be overcome by more substrate.
Inhibitor table
| Pattern | Km | Vmax | Mechanism |
|---|---|---|---|
| Competitive | Increases | Same | Substrate can outcompete inhibitor |
| Noncompetitive | Same | Decreases | Active enzyme capacity falls |
| Uncompetitive | Decreases | Decreases | Inhibitor binds enzyme-substrate complex |
| Mixed | Changes | Decreases | Binding and catalysis both shift |
Review rule
When a graph question is missed, write the change in words before writing the answer. "Same Vmax, higher Km" is easier to reason from than a memorized line intersection.
Next step
Connect kinetics to amino acids, active-site chemistry, and experimental design. Most MCAT kinetics passages are really asking how a molecular change becomes a measurable rate change.