Glycerol is a triol with a structure of propane substituted at positions 1, 2 and 3 by hydroxy groups. It has a role as an osmolyte, a solvent, a detergent, a human metabolite, an algal metabolite, a Saccharomyces cerevisiae metabolite, an Escherichia coli metabolite, a mouse metabolite and a geroprotector. It is an alditol and a triol. Glycerine appears as a colorless to brown colored liquid. Combustible but may require some effort to ignite.