Glycosaminoglycans (GAGs) are long, unbranched polysaccharides that play a key role in the structural integrity and function of connective tissues. They are composed of repeating disaccharide units and contribute to cellular processes like proliferation, cell adhesion, and wound healing. GAG analysis is crucial in diagnosing disorders related to connective tissue and metabolic imbalances, as altered GAG levels can indicate conditions such as mucopolysaccharidoses and other lysosomal storage disorders.