88 CHAPTER 26 LIPIDS ipids differ from the other classes of naturally occurring biomolecules(carbohy drates, proteins, and nucleic acids) in that they are more soluble in non-to-weakly polar solvents(diethyl ether, hexane, dichloromethane) than they are in water. They include a variety of structural types, a collection of which is introduced in this chapter. heti o n spite of the number of different structural types, lipids share a common biosyn- bohydrate metabolism, called glycolysis, glucose is converted to lactic acid. Pyruvic acid C6H1206->CH3CCO2H CH3CHCOH Pyruvic acid In most biochemical reactions the pH of the medium is close to 7. At this pH, carboxylic acids are nearly completely converted to their conjugate bases. Thus, it is common practice in biological chemistry to specify the derived carboxylate anion rather than the carboxylic acid itself. For example, we say that glycolysis leads to lactate by way of pyrvate the pyruvate is used by living systems in a number of different ways. One pathway, he leading to lactate and beyond, is concerned with energy storage and production This is not the only pathway available to pyruvate, however. A significant fraction of it is converted to acetate for use as a starting material in the biosynthesis of more com- plex substances, especially lipids. By far the major source of lipids is biosynthesis via acetate and this chapter is organized around that theme. We'll begin by looking at the reaction in which acetate(two carbons) is formed from pyruvate(three carbons). 1015 Back Forward Main MenuToc Study Guide ToC Student o MHHE Website1015 CHAPTER 26 LIPIDS L ipids differ from the other classes of naturally occurring biomolecules (carbohy￾drates, proteins, and nucleic acids) in that they are more soluble in non-to-weakly polar solvents (diethyl ether, hexane, dichloromethane) than they are in water. They include a variety of structural types, a collection of which is introduced in this chapter. In spite of the number of different structural types, lipids share a common biosyn￾thetic origin in that they are ultimately derived from glucose. During one stage of car￾bohydrate metabolism, called glycolysis, glucose is converted to lactic acid. Pyruvic acid is an intermediate. In most biochemical reactions the pH of the medium is close to 7. At this pH, carboxylic acids are nearly completely converted to their conjugate bases. Thus, it is common practice in biological chemistry to specify the derived carboxylate anion rather than the carboxylic acid itself. For example, we say that glycolysis leads to lactate by way of pyruvate. Pyruvate is used by living systems in a number of different ways. One pathway, the one leading to lactate and beyond, is concerned with energy storage and production. This is not the only pathway available to pyruvate, however. A significant fraction of it is converted to acetate for use as a starting material in the biosynthesis of more com￾plex substances, especially lipids. By far the major source of lipids is biosynthesis via acetate and this chapter is organized around that theme. We’ll begin by looking at the reaction in which acetate (two carbons) is formed from pyruvate (three carbons). C6H12O6 Glucose O CH3CCO2H Pyruvic acid OH CH3CHCO2H Lactic acid Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website