Some aspects of the evolution of vertebrate acid-base regulation.
نویسندگان
چکیده
The H2CO3-HCO3system in vertebrates did not evolve directly from the original forms of life. Organic evolution probably dates back some 109 years.1 Although there may have been small amounts of CO2 present in the atmosphere and CO2 was definitely present in the earth mantle, it is generally accepted that metabolic pathways were anaerobic in nature. This conclusion is based on several lines of evidence. The primitive atmosphere contained no free oxygen and any free oxygen formed from the photolysis or electrolysis of water could not have accumulated in the reducing atmosphere present at that time. If adequate concentrations of molecular 02 in the atmosphere only arose from the metabolic activity of living forms, the original forms must have developed anaerobically.1 Anaerobic metabolic processes in all existing organisms are very similar while oxidative processes are more variable; therefore, anaerobic metabolism would appear to be more primitive.2 Biosynthetic processes requiring 02 commonly have preliminary steps that are anaerobic. The biosynthesis of a number of important biological substances that are 02 requiring in relatively higher forms are carried out by entirely anaerobic mechanisms in
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ورودعنوان ژورنال:
- The Yale Journal of Biology and Medicine
دوره 41 شماره
صفحات -
تاریخ انتشار 1969