While they are both structurally acids, they have very different functions. Glycolic Acid increases cell turnover by breaking down the bonds that hold skin cells together. Hyaluronic Acid, however, is a group of sugar molecules that are naturally produced in the body (which can also be sourced from plant matter) and has a primary function of retaining moisture. It is primarily found in your skin and connective tissues to keep your body hydrated and flexible.