Question

a noncompetitive inhibitor reduces the rate of a reaction by - binding to the active site. lowering the activation energy. binding to the substrate. changing the shape of the active site. increasing the \\( delta g \\) of the reaction.

Explanation:

1. Analyze option A: Binding to the active site is the mechanism of competitive inhibitors, not noncompetitive, so A is incorrect.
2. Analyze option B: Enzymes (and catalysts) lower activation energy; inhibitors reduce reaction rate, so B is incorrect.
3. Analyze option C: Noncompetitive inhibitors do not bind to the substrate, so C is incorrect.
4. Analyze option D: Noncompetitive inhibitors bind to an allosteric site, which changes the shape of the active site, reducing the enzyme's ability to catalyze the reaction, so D is correct.
5. Analyze option E: Inhibitors do not change the Gibbs free energy ($\Delta G$) of the reaction; $\Delta G$ is related to the spontaneity of the reaction, not the rate, so E is incorrect.

Answer:

D. changing the shape of the active site.