Which statement correctly describes reducing sugars in Benedict's test?

Which statement correctly describes reducing sugars in Benedict's test?

• A. They can donate electrons to reduce other molecules.
• B. They can only be monosaccharides.
• C. They do not react with Benedict's reagent.
• D. They are nonpolar and insoluble in water.

Answer: (A)

Reducing sugars can donate electrons to other molecules because they have a free aldehyde or ketone group that can be oxidized. In Benedict's test, that electron donation reduces the copper(II) ions in the reagent to copper(I) oxide, which appears as a color change from blue to green, yellow, orange, or brick red depending on how much sugar is present. This is why the statement about reducing sugars acting as reducing agents is the best description. Some sugars that aren’t just simple monosaccharides can also act as reducing sugars, like maltose or lactose, so they aren’t limited to monosaccharides. They do react with Benedict’s reagent, so saying they don’t react is incorrect. Sugars are polar and water-soluble because of their multiple hydroxyl groups, so labeling them as nonpolar and insoluble isn’t accurate.

Reducing sugars can donate electrons to other molecules because they have a free aldehyde or ketone group that can be oxidized. In Benedict's test, that electron donation reduces the copper(II) ions in the reagent to copper(I) oxide, which appears as a color change from blue to green, yellow, orange, or brick red depending on how much sugar is present. This is why the statement about reducing sugars acting as reducing agents is the best description.

Some sugars that aren’t just simple monosaccharides can also act as reducing sugars, like maltose or lactose, so they aren’t limited to monosaccharides. They do react with Benedict’s reagent, so saying they don’t react is incorrect. Sugars are polar and water-soluble because of their multiple hydroxyl groups, so labeling them as nonpolar and insoluble isn’t accurate.