Схема. Стадии гликолиза = Stages of glycolysis. Перевести на русский язык = Translate into Russian Модификация: Berg J.M., Tymoczko J.L., Stryer L. Biochemistry. 7th ed., W H Freeman, 2012, 1224 p. см.: Биохимия человека: Литература. Иллюстрации.

Примечание:

The glycolytic pathway can be divided into two stages: (1) glucose is trapped, destabilized, and cleaved into two interconvertible three-carbon molecules generated by cleavage of six-carbon fructose; and (2) ATP is generated. The first metabolic pathway that we encounter is glycolysis, an ancient pathway employed by a host of organisms. Glycolysis is the sequence of reactions that metabolizes one molecule of glucose to two molecules of pyruvate with the concomitant net production of two molecules of ATP. This process is anaerobic (i.e., it does not require O2) because it evolved before substantial amounts of oxygen accumulated in the atmosphere. Pyruvate can be further processed anaerobically to lactate (lactic acid fermentation) or ethanol (alcoholic fermentation). Under aerobic conditions, pyruvate can be completely oxidized to CO2, generating much more ATP, as will be described in Chapters 17 and 18. Figure 16.1 shows some possible fates of pyruvate produced by glycolysis. Because glucose is such a precious fuel, metabolic products, such as pyruvate and lactate, are salvaged to synthesize glucose in the process of gluconeogenesis. Although glycolysis and gluconeogenesis have some enzymes in common, the two pathways are not simply the reverse of each other. In particular, the highly exergonic, irreversible steps of glycolysis are bypassed in gluconeogenesis. The two pathways are reciprocally regulated so that glycolysis and gluconeogenesis do not take place simultaneously in the same cell to a significant extent. Our understanding of glucose metabolism, especially glycolysis, has a rich history. Indeed, the development of biochemistry and the delineation of glycolysis went hand in hand. A key discovery was made by Hans Buchner and Eduard Buchner in 1897, quite by accident. The Buchners were interested in manufacturing cell-free extracts of yeast for possible therapeutic use. These extracts had to be preserved without the use of antiseptics such as phenol, and so they decided to try sucrose, a commonly used preservative in kitchen chemistry. They obtained a startling result: sucrose was rapidly fermented into alcohol by the yeast juice. The significance of this finding was immense. The Buchners demonstrated for the first time that fermentation could take place outside living cells. The accepted view of their day, asserted by Louis Pasteur in 1860, was that fermentation is inextricably tied to living cells. The chance discovery by the Buchners refuted this dogma and opened the door to modern biochemistry. The Buchners’ discovery inspired the search for the biochemicals that catalyze the conversion of sucrose into alcohol. The study of metabolism became the study of chemistry. Studies of muscle extracts then showed that many of the reactions of lactic acid fermentation were the same as those of alcoholic fermentation. This exciting discovery revealed an underlying unity in biochemistry. The complete glycolytic pathway was elucidated by 1940, largely through the pioneering contributions of Gustav Embden, Otto Meyerhof, Carl Neuberg, Jacob Parnas, Otto Warburg, Gerty Cori, and Carl Cori. Glycolysis is also known as the Embden–Meyerhof pathway.