Complex polysaccharide complexes of varying sizes. May be up to several million Daltons. Part of membrane complexes or the extracellular matrix. Some classes on cells bind growth factors, and may be a kind of antennae to collect and store these factors. In connective tissues the very hydroscopic complexes bind water and serve to cushion joints.
Cartilage is flexible and resilient because of proteoglycans.
Examples of some of the repeating disaccharides of proteoglycans. Notice that long polymers would be extended with multiple negative charges. Heparin , an example of structure containing acidic repeating disaccharide units. A cartoon of a proteoglycan complex of connective tissue. Hurler's syndrome is one example of a lysosomal storage disease, caused by loss of a degradative enzyme.