Sialic Acids

Definition: 

Acidic sugar molecules prominently found at the outermost fringes of the forest of sugar chains (glycans) that cover all vertebrate cells. The two most common sialic acids in mammals are N-acetylneuraminic acid (Neu5Ac) into N glycolylneuraminic acid (Neu5Gc). The human lineage ceased the ability to produce Neu5Gc over 2 million years ago causing human cells to be coated with an excess of Neu5Ac.