The copper reduction reaction in stool is used to detect which type of substances?

The copper reduction reaction in stool is used to detect which type of substances?

• A. Reducing substances
• B. Nonreducing sugars
• C. Proteins
• D. Lipids

Answer: (A)

The test is designed to detect reducing substances—compounds that can donate electrons to copper(II) ions in alkaline solution. In stool, unabsorbed reducing sugars such as glucose and lactose can reduce cupric ions to cuprous oxide, causing a color change or precipitate that indicates a positive result. Nonreducing sugars (like sucrose) don’t react unless they’re hydrolyzed to reducing sugars first, so they won’t give a positive result on this test. Proteins and lipids don’t have the redox properties needed to reduce copper in this assay, so they don’t cause the characteristic color change.

The test is designed to detect reducing substances—compounds that can donate electrons to copper(II) ions in alkaline solution. In stool, unabsorbed reducing sugars such as glucose and lactose can reduce cupric ions to cuprous oxide, causing a color change or precipitate that indicates a positive result. Nonreducing sugars (like sucrose) don’t react unless they’re hydrolyzed to reducing sugars first, so they won’t give a positive result on this test. Proteins and lipids don’t have the redox properties needed to reduce copper in this assay, so they don’t cause the characteristic color change.