Q.31 Slow intravenous infusion of ethanol is a therapy to treat methanol poisoning. The
underlying chemical reaction is an example of
(A)Competitive inhibition
(B) Non-competitive inhibition
(C) Mixed inhibition
(D)Enzyme activation
Slow intravenous infusion of ethanol treats methanol poisoning through competitive inhibition of alcohol dehydrogenase. This mechanism prevents formation of toxic metabolites like formaldehyde and formic acid. The correct answer is (A) Competitive inhibition.
Mechanism in Methanol Poisoning
Methanol poisoning occurs when alcohol dehydrogenase (ADH) converts methanol to toxic formaldehyde and formic acid, causing metabolic acidosis and optic nerve damage. Ethanol, structurally similar to methanol, has higher affinity for ADH’s active site, binding preferentially and blocking methanol oxidation. Slow IV infusion maintains ethanol levels to sustain this inhibition until methanol is excreted.
Option Explanations
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(A) Competitive inhibition: Ethanol competes with methanol for ADH’s active site due to structural similarity, reducing methanol metabolism. Effects reverse with higher substrate concentration.
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(B) Non-competitive inhibition: Inhibitor binds allosteric site, altering enzyme shape without active site competition. Ethanol targets the active site, not allosteric.
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(C) Mixed inhibition: Inhibitor binds both active and allosteric sites, affecting Vmax and Km variably. ADH inhibition by ethanol is purely competitive.
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(D) Enzyme activation: Increases enzyme activity or expression. Ethanol inhibits, not activates, ADH.
