Glycosidic bond, protein-carbohydrate complexes

The molecule to the left is the disaccharide sucrose. Many sugars linked together form a polysaccharide, and the term complex carbohydrate is used for these structures. More than two glycosidic bonds may attach to a simple sugar, so complex carbohydrates often contain branch-like structures. This is in contrast to proteins where building blocks are strung together in a linear fashion. 

Monosaccharides consist of only one sugar unit. Oligosaccharides consist of between two and ten of the same or different monosaccharides connected to each other by glycosidic (semiacetal) bonds. Monosaccharides and oligosaccharides are sometimes referred to collectively by the name sugars, as they share many common properties and often have a sweet taste. Polysaccharides are composed of more than ten of the same or different monosaccharides commonly they consist of multiple molecules of monosaccharides, which are often precisely determined. Complex carbohydrates also contain compounds other than saccharides, such as, for example, peptides, proteins and lipids. 

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