Sialic acids are a family of 9 carbon alpha-keto acids that are usually present in the non reducing terminal of glycoconjuates on the cell surface of eukaryotic cells. These sialylated conjugates play important roles in cell recognition and signaling, neuronal development, cancer metastasis and bacterial or viral infection. More than 50 forms of sialic acid are found in nature, the most abundant being N-acetylneuraminic acid (Neu5Ac, N-acetylneuraminate) (Li & Chen 2012, Wickramasinghe & Medrano 2011). The steps below describe the biosynthesis, transport, utilization and degradation of Neu5Ac in humans.