Chapter 24: Carbohydrates

Carbohydrates integrates organic chemistry principles with biochemical processes by examining metabolic pathways through the lens of reaction mechanisms. The material demonstrates how fundamental organic transformations including nucleophilic substitution, addition, elimination, oxidation, and reduction operate within living cells to sustain life processes. Students explore three major metabolic pathways—glycolysis, the citric acid cycle, and fatty acid β-oxidation—understanding how each pathway represents a series of carefully orchestrated organic reactions catalyzed by enzymes. The chapter emphasizes the role of coenzymes such as NAD⁺ and FAD in facilitating electron transfer and energy capture, while ATP serves as the primary currency for energy transfer within cells. Central to this exploration is the concept of biological electrophiles and nucleophiles, showing how substrate molecules are activated for subsequent transformations. Key mechanistic themes include carbonyl group activation, acyl transfer reactions, and phosphorylation events that occur in nearly every metabolic process. By connecting functional group chemistry to biochemical outcomes, the chapter reveals how enzyme-catalyzed mechanisms follow the same fundamental organic chemistry principles taught in earlier chapters, simply operating in an aqueous biological environment with remarkable selectivity and efficiency. The use of curved-arrow notation to annotate enzymatic mechanisms provides students with visual understanding of electron movement and bond formation within living systems. This integrated approach prepares students to recognize organic chemistry not as an abstract subject but as the molecular basis underlying all biological function, laying essential groundwork for advanced study in biochemistry, pharmacology, and medicinal chemistry.