The alcohol reacting with the hemi-acetal is the OH group on another monosaccharide . The bond between the monosaccharides is called a glycoside bond. One of the anomeric carbons must be involved in the glycoside bond . It forms between C 1 of galactose and the -OH residue on C 4 of glucose. This is called a b -1,4 glycoside because the bond is formed between C 1 and C 4 .
Lactose is milk sugar, the only carbohydrate source naturally available to infants.
Lactose can not be absorbed through the intestinal walls into the bloodstream. It must first be hydrolyzed back into glucose and galactose. Infants have an enzyme, lactase , which catalyzes this reaction. This is referred to as lactose intolerance. Let's look at the formation of the most abundant disaccharide on earth, sucrose .