. Analysis of development. Embryology; Embryology. Cell Constitution 71 and synthesis separately. They apparently may be dissociated in cells by such agents as dinitrophenol, and off-on switching devices between the two phases of metabolism may well be operative in nor- mal physiological control. There is abundant evidence that at temperatures in the physiological range, the downhill release of energy to be used by the uphill synthetic paths cannot involve a simple transfer of heat such as one finds in the usual heat expansion type of ma- chine. Rather, it has become obvious that chemical form
. Analysis of development. Embryology; Embryology. Cell Constitution 71 and synthesis separately. They apparently may be dissociated in cells by such agents as dinitrophenol, and off-on switching devices between the two phases of metabolism may well be operative in nor- mal physiological control. There is abundant evidence that at temperatures in the physiological range, the downhill release of energy to be used by the uphill synthetic paths cannot involve a simple transfer of heat such as one finds in the usual heat expansion type of ma- chine. Rather, it has become obvious that chemical forms of linkage energy must be made available. These chemical links must be such that they can be formed by the oxidative pathways and then enter into reactions with the synthetic pathways, giving up their high energy content for purposes of chemical synthesis, transport of materials, gross movements and so forth (cf. Johnson, in Lardy, '50).* A good rule-of-thumb to keep in mind is that, in order for an energy-yielding (exergonic) reac- tion to drive an energy-using (endergonic) reaction, the two reactions must have a common component. It is apparent that the whole study of cellular metabolism involves a number of aspects. Starting with the outside of the ani- mal cell and working inward we may list the following: 1. The exchange of foods and waste prod- ucts between cell and environment. Under this heading are frequently listed such sub- jects as permeability, secretion, and excre- tion. Although of obvious importance, these subjects will be treated only incidentally here. 2. The oxidative breakdown of the re- duced carbon chains of the foods taken in. 3. Formation of energy linkage compounds. It is here that the coenzyme systems become of greatest importance. Three systems will be invoked frequently (cf. Meyerhof, '49): the coenzyme I and II systems (nicotinamide coenzymes) concerned with hydrogen (elec- tron) transfer; the adenylic acid systems (ATP and ADP) concerned with pho
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Keywords: ., bookcentury1900, bookpublisherphiladelphi, booksubjectembryology
