This chapter begins a series of three chapters that examine the molecular logic of specific degradative or biosynthetic pathways involving three iconic metabolites: glucose, squalene, and porphobilinogen. This chapter examines three major metabolic roles for glucose, one catabolic, two anabolic. In the catabolic role of glucose-6-P as a major energy source the chemical and enzymatic logic for its complete oxidation to six CO₂ with storage of its 24 bonding electrons are saved as 12 hydride equivalents in NADH and FADH₂ are explored through both glycolysis and the citric acid cycle. The two biosynthetic pathways for glucose-6-P are the pentose-P pathway, generating ribose for all nucleic acid building blocks, and the transfer of glycosyl groups as electrophilic fragments at carbon 1 in polysaccharide biosynthesis. The array of hydroxycarbonyl group chemistry and the several alcohol to ketone oxidations of glucose illustrate a biologic universe of carbonyl chemistry.