Biology – Carbohydrates and lipids | e-Consult

The table shows that glucose, fructose, and maltose all have a free aldehyde or ketone group, which allows them to act as reducing sugars. Sucrose, despite having the same chemical formula as these reducing sugars, is classified as a non-reducing sugar because its reducing groups (the aldehyde and ketone groups) are involved in a terminal glycosidic bond. This bond is part of the main sugar chain and cannot be easily broken. Therefore, the reducing groups are effectively 'locked' within the structure and cannot participate in the reduction reaction.