The link between a protein molecule and its prosthetic group is a covalent bond (an electron-sharing bond) in the glycoproteins, the biliproteins, and some of the heme proteins. In lipoproteins,

…is a mixture of several conjugated proteins. The best known are an α-lipoprotein (combination of lipid and protein) and two mucoproteins (combinations of carbohydrate and protein). One mucoprotein is called orosomucoid, or α₁-acid glycoprotein; the other is called haptoglobin because it combines specifically with globin, the protein component of hemoglobin.…

…of proteins has been called conjugated proteins, because they are complex molecules of protein consisting of protein and nonprotein moieties. The nonprotein portion is called the prosthetic group. Conjugated proteins can be subdivided into mucoproteins, which, in addition to protein, contain carbohydrate; lipoproteins, which contain lipids; phosphoproteins, which are rich…