Explain why cellobiose and lactose are considered reducing disaccharides, whereas the disaccharide trehalose is considered non-reducing.

Cellobiose and lactose have fewer glucose units, which makes them available for reduction. In contrast, trehalose has more glucose units, which makes it a nonreducible sugar.

Cellobiose and lactose have β(1→4) glycosidic bonds, which can be heated into a straight chain that contains a ketone group that can be reduced. In contrast, trehalose has α(1→1) glycosidic bonds, which cannot be heated into a reducible straight chain.

Cellobiose and lactose have a cyclic acetal group, which can be hydrolyzed into a straight chain that contains an aldehyde group that can be reduced. In contrast, trehalose has a hemiacetal group, which cannot be hydrolyzed into a reducible straight chain.

Cellobiose and lactose have a cyclic hemiacetal group, which can be hydrolyzed into a straight chain that contains an aldehyde group that can be reduced. In contrast, trehalose has an acetal group, which cannot be hydrolyzed into a reducible straight chain.