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6231180 
Book/Book Chapter 
10 - ASSIMILATION OF CARBON DIOXIDE 
Broda, E 
1975 
Pergamon 
The Evolution of the Bioenergetic Processes 
68-73 
Publisher Summary This chapter discusses the assimilation of carbon dioxide. Major amounts of CO2 are fixed by cyclic processes developed for this purpose. On the basis of the evidence from extant organisms, the photoorganotrophs were, with the possible exception of the methane formers, the first bacteria to do so. They use organic compounds or hydrogen as source of electrons, and light as source of energy for assimilation. In cyclic processes at the end of a series of reactions, the acceptor for CO2 is regenerated. Generally after a time, all carbon atoms in the net products are ultimately derived from CO2. Cyclic processes are efficient. In assimilation by a cyclic process, carbon is fixed on a kind of moving belt. All this would not apply to linear processes, such as to the carboxylation of pyruvic acid. The oxaloacetate formed is largely diverted as a net product, and new pyruvate for its synthesis therefore has to come from a source other than CO2. 
Broda, E.