Lactose Principal sugar in milk O O H O H CH2 O H O O H O H CH2 O H O O H O H 4-0-b-D-Galactopyranosyl (1->4)-a-D- Glucopyranose 4-0-b-D-Galactopyranosyl (1->4)-b-D-GlucopyranoseLactose Principal sugar in milk O O H O H CH2 O H O O H O H CH2 O H O O H O H 4-0-b-D-Galactopyranosyl (1->4)-a-D- Glucopyranose 4-0-b-D-Galactopyranosyl (1->4)-b-D-Glucopyranose