Galactolipids are a type of glycolipid whose sugar group is galactose. They're different from glycosphingolipids in that they do not have nitrogen in their composition.[1]
They are the main part of plant membrane lipids where they substitute phospholipids to conserve phosphate for other essential processes. These chloroplast membranes contain a high quantity of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG).
They probably also assume a direct role in photosynthesis, as they have been found in the X-ray structures of photosynthetic complexes.[2]
The galactolipid galactocerebroside (GalC) and its sulfated derivative sulfatide is also in abundance present (together with a small group of proteins) in myelin, the membrane around the axons in the nervous system of vertebrates.[3]