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Multiple Choice
Identify the following disaccharides as reducing sugars (RS) or non-reducing sugars (NS)
A
maltose = RS; sucrose = RS; lactose NS
B
maltose = RS; sucrose = NS; lactose NS
C
maltose = RS; sucrose = NS; lactose RS
D
maltose = NS; sucrose = RS; lactose NS
Verified step by step guidance
1
Identify the anomeric carbon in each monosaccharide unit of the disaccharides. The anomeric carbon is the carbon attached to two oxygen atoms, one in the ring and one in the hydroxyl group.
Determine if the anomeric carbon is free or involved in a glycosidic bond. A free anomeric carbon indicates a reducing sugar, while an anomeric carbon involved in a glycosidic bond indicates a non-reducing sugar.
For maltose, observe that the anomeric carbon of the glucose unit on the right is free, making maltose a reducing sugar (RS).
For sucrose, note that both anomeric carbons are involved in the glycosidic bond, making sucrose a non-reducing sugar (NS).
For lactose, observe that the anomeric carbon of the glucose unit on the right is free, making lactose a reducing sugar (RS).