Which of the following is a reducing sugar?

  • A. Sucrose
  • B. Starch
  • C. Maltose
  • D. Cellulose

Explanation

Maltose keeps a free anomeric carbon, so its open-chain form has an aldehyde group that reduces Benedict's reagent to a brick red precipitate. In sucrose both anomeric carbons are locked into the glycosidic bond, which is why it is the classic non-reducing disaccharide. Starch and cellulose are polysaccharides with only one free end in an enormous molecule, so no detectable reduction occurs.

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