Chapter 8: Nucleotides and Nucleic Acids: Structure, Chemistry, and Biological Functions

Nucleotides and Nucleic Acids: Structure, Chemistry, and Biological Functions begins by classifying carbohydrates based on the number of carbon atoms and functional groups, distinguishing between monosaccharides (simple sugars), oligosaccharides, and polysaccharides. Section 8.1 introduces monosaccharides, such as glucose, fructose, and ribose, and explains their stereochemistry, epimerization, and ring formation through hemiacetal and hemiketal linkages. Fischer and Haworth projections are used to depict sugar structures, and the anomeric carbon is identified as the basis of α and β forms. Section 8.2 focuses on disaccharides and polysaccharides, exploring glycosidic bonds and the importance of linkages in determining polymer function. Notable examples include maltose, lactose, and sucrose as disaccharides, as well as structural polysaccharides like cellulose and chitin, and storage polysaccharides like starch and glycogen. It discusses how the branching of glycogen and amylopectin increases solubility and enzymatic accessibility. Section 8.3 introduces glycoconjugates, including glycoproteins, proteoglycans, and glycolipids, highlighting their roles in signaling, structural integrity, and immune recognition. N-linked and O-linked glycosylation are examined in the context of protein processing and membrane localization. Section 8.4 explores lectins—carbohydrate-binding proteins—and their role in mediating cell-cell recognition, infection pathways, and immune responses. Important biological systems such as the ABO blood group antigens and viral entry mechanisms are used to demonstrate the specificity of carbohydrate interactions. The chapter closes by introducing glycomics, a growing field focused on understanding the glycan code, and the analytical techniques used to study complex carbohydrates. By the end, readers understand how carbohydrates are more than just energy sources—they are central to structural biology, cell communication, and disease mechanisms.