**Core Concept**
Non-competitive inhibition is a type of enzyme inhibition where an inhibitor binds to a site other than the active site of the enzyme, altering the enzyme's shape and reducing its ability to bind to the substrate. This results in a decrease in the enzyme's maximal velocity (Vmax) without affecting its affinity for the substrate (Km).

**Why the Correct Answer is Right**
The correct answer, **Option A: Potency reduced**, is incorrect because non-competitive inhibition actually reduces the maximal velocity (Vmax) of the enzyme, not its potency. Potency refers to the concentration of the substrate required to achieve a particular effect, which remains unchanged in non-competitive inhibition. The enzyme's ability to bind to the substrate (Km) is also unaffected.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is incorrect because non-competitive inhibition does not reduce the potency of the enzyme, but rather its maximal velocity (Vmax).
**Option B:** Km remains unchanged in non-competitive inhibition, as the inhibitor binds to a site other than the active site and does not affect the enzyme's affinity for the substrate.
**Option D:** Non-competitive inhibition involves the binding of an inhibitor to a site other than the active site of the enzyme, but this is not the correct description of the phenomenon.

**Clinical Pearl / High-Yield Fact**
In non-competitive inhibition, the inhibitor binds to a site other than the active site of the enzyme, resulting in a decrease in the enzyme's maximal velocity (Vmax) without affecting its affinity for the substrate (Km). This type of inhibition is often seen with enzymes that have allosteric sites, which can bind to molecules other than the substrate.

**✓ Correct Answer: A. Potency reduced**