Glycolipids are carbohydrate-attached lipids that can be extracted from algal biomass. Their role is to provide energy and to serve as markers for cellular recognition owing to their association with cell membranes.

Red algae contain monoglycosyldiacylglycerol (MGDG), diglycosyldiacylglycerol (DGDG), and sulphaquinovosyldiacyl-glycerol at essentially similar levels. Conversely, MGDG and DGDG are the chief glycolipids in green algae. On the other hand, the MGDG content of brown algae varies from 26-47%, the DGDG content from 20-44%, and the ulphaquinovosylglycerol content from 18-52% of the total glycolipids (Dembitsky and Rozentsvet, 1990).