Galactose and fructose are both structural isomers of glucose. All three substances share the same molecular formula of C6H12O6; however, all three have a unique arrangement of their atoms structurally.
Glucose, galactose and fructose are all hexose monosaccharides with the molecular formula C6H12O6. Galactose is found in milk and yogurt. It is similar to glucose in that it is a six-membered ring. In galactose, the hydroxyl group attached to the fourth carbon projects the opposite direction spatially as it is found in glucose. Fructose is a sugar found in honey. The atoms in fructose arrange to form a five-membered ring rather than the six-membered ring found in glucose and galactose.