the high number of publications on sialic acids from the time of their discovery reflects the increasing interest on these acids in areas such as their chemical composition ( 16 different sialic acids are now recognized ) , their distribution in nature ( a not yet well explained topic ) , their metabolism ( which shows differences between bacteria and animal cells ) and their biological roles , mainly as a part of glycoproteins and gangliosides ( as receptors , markers of the cytoplasmic membrane , viscosity agents of the glycoproteins , life regulators of some substances , etc . ) .
C0007634
cells
C0007603
cytoplasmic membrane