Hyaluronic Acid
Definition and meaning of Hyaluronic Acid in chemistry.
Hyaluronic acid is a naturally occurring polysaccharide made of repeating disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine, joined by alternating beta-1,4 and beta-1,3 glycosidic bonds into a long, unbranched chain.
In more detail
It belongs to the glycosaminoglycan family but, unlike chondroitin sulfate or heparin, carries no sulfate groups; its many hydroxyl and carboxylate groups hydrogen-bond extensively with water, letting the polymer absorb many times its own weight in water and form viscous, gel-like solutions. This water-holding, lubricating, and shock-absorbing behavior makes it a major component of synovial fluid, the vitreous humor of the eye, and the skin's extracellular matrix. In the body it is built at the inner face of the plasma membrane by hyaluronan synthase enzymes rather than in the Golgi apparatus, and chain lengths can reach into the millions of daltons. Its water-binding properties are also exploited in dermal fillers, joint-injection therapies, and moisturizing skincare products.
Key facts
| Formula (repeating disaccharide unit) | (C14H21NO11)n |
|---|---|
| Molar mass of repeat unit | ~379.3 g/mol; full polymer often 10^5-10^7 g/mol |
| Class | Non-sulfated glycosaminoglycan (polysaccharide) |
| Field | Biochemistry |
In the synovial fluid of the knee joint, hyaluronic acid coats the cartilage surfaces and thickens the fluid, letting the bones glide over one another with very little friction.
Frequently asked questions
Is hyaluronic acid the same as hyaluronan?
Essentially yes. "Hyaluronan" refers to the polymer in its physiological, ionized (salt) form, while "hyaluronic acid" denotes the protonated acid form; the two names are used interchangeably in most contexts.
Why does hyaluronic acid hydrate skin so effectively?
Its carboxylate and hydroxyl groups form extensive hydrogen bonds with water molecules, allowing the polymer to bind many times its own weight in water and create a moisture-retaining gel on the skin's surface.