--- title: "Enzyme Inhibition and Metabolic Control" description: "Competitive inhibition raises apparent Km without lowering Vmax. Pure non-competitive inhibition lowers Vmax without changing Km. Reversible end-product inhibition lets accumulated products reduce the" canonical: https://lightmysky.com/learn/science/enzyme-inhibition-and-metabolic-control-mt_8VYolkJ_wR source: https://lightmysky.com/learn/science/enzyme-inhibition-and-metabolic-control-mt_8VYolkJ_wR.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Enzyme Inhibition and Metabolic Control Competitive inhibition raises apparent Km without lowering Vmax. Pure non-competitive inhibition lowers Vmax without changing Km. Reversible end-product inhibition lets accumulated products reduce their own production. Subject: Science · Area: Organisms & Life Processes · Ages 17 to 18 Page: https://lightmysky.com/learn/science/enzyme-inhibition-and-metabolic-control-mt_8VYolkJ_wR ## Ready when they can - Predicts how competitive, pure non-competitive and uncompetitive inhibition affect Vmax and apparent Km. - Explains why separate-site binding alone does not establish pure non-competitive inhibition and why extra substrate does not restore its Vmax. - Describes reversible end-product inhibition as a feedback control loop. ## Lesson: Read what inhibitors do to enzymes Measure initial rates at fixed enzyme concentration, temperature and pH. Hold inhibitor concentration fixed as substrate varies. In reversible competitive inhibition, substrate and inhibitor cannot bind the enzyme together. This can involve the active site or mutually exclusive binding at separate sites. More substrate reduces inhibition: Vmax stays unchanged, while apparent Km rises. **Example.** Vmax is the limiting rate at high substrate concentration. Km is the substrate concentration giving half of that curve's Vmax. Suppose the control has Vmax 12 rate units and Km 3 mmol/L. A competitive inhibitor leaves Vmax at 12 but raises apparent Km to 9 mmol/L. Both curves reach 6 rate units at their own Km; the inhibited reaction needs more substrate. *(drawing: These cells show the parameter pattern, not a rate curve.)* A pure non-competitive inhibitor binds away from the active site with equal affinity to free enzyme and enzyme with substrate bound. Substrate can still bind, but inhibitor-bound enzyme cannot catalyse the reaction. Vmax falls and Km stays unchanged. Extra substrate cannot restore the control Vmax because it does not prevent this inhibitor from binding. Separate-site binding alone does not prove pure non-competitive inhibition. Pure non-competitive inhibition is a special case of mixed inhibition. Other mixed inhibitors lower Vmax and may raise or lower apparent Km. An uncompetitive inhibitor binds only to the enzyme-substrate complex; Vmax and apparent Km decrease by the same factor. In end-product inhibition, accumulated product inhibits an earlier regulatory enzyme, often at an allosteric site away from the active site. Production slows. If product use exceeds production, the product pool falls. With reversible binding, less product then remains bound and enzyme activity can recover. This feedback does not require enzyme destruction or a pure non-competitive rate pattern. *(drawing: The product pool falls only when product use exceeds its formation.)* ATP and ADP help regulate cellular respiration. High ATP availability can inhibit some regulatory enzymes, reducing further ATP production. A rise in ADP relative to ATP can activate some enzymes and increase respiration. The response depends on the enzyme and other conditions. ATP does not inhibit every enzyme, and ADP does not directly remove every inhibitor. In competitive inhibition, substrate and inhibitor binding are mutually exclusive. Raising substrate reduces inhibitor occupancy, so the rate approaches the unchanged control Vmax. A pure non-competitive inhibitor can also bind enzyme with substrate bound. Extra substrate cannot prevent its inhibition, so the rate approaches a lower Vmax. Increasing substrate changes the measured rate; it does not raise competitive Vmax. **Recap.** Competitive inhibition raises apparent Km. Pure non-competitive inhibition lowers Vmax. Reversible product feedback adjusts pathway activity. *Lesson, questions and flashcards written for this dataset. Khan Academy articles on enzyme kinetics and regulation and OpenStax's Regulation of Cellular Respiration were consulted for biological facts.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Enzyme Kinetics: Vmax and the Michaelis Constant](https://lightmysky.com/learn/science/enzyme-kinetics-vmax-and-the-michaelis-constant-mt_ooF8eZ1Gzy) ## Opens up - [Double-Reciprocal Plots and Telling Inhibitor Types Apart](https://lightmysky.com/learn/science/double-reciprocal-plots-and-telling-inhibitor-types-apart-mt_9y397ROu9X) - [From Hit to Lead: Structure-Activity Relationships](https://lightmysky.com/learn/science/from-hit-to-lead-structure-activity-relationships-mt_p53KgFKAUg)