Photosynthesis and Cellular Respiration

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The first part of this paper compares and contrasts two plant processes - photosynthesis and cellular respiration. While it is acknowledged that the former process precedes the latter one by a few billion years the two processes do have complementary functions.


Phylogenetic analysis of Mg-tetrapyrrole biosynthesis genes reveals that anoxygenic photosynthetic processes became evident in primitive organisms like certain bacteria before the oxygenic variety in other organisms like cyanobacteria (Xiong and Bauer, 2002). Joint analyses of the pigment genes and reaction centers have yielded stronger evidence to this effect (Xiong and Bauer, 2002). At the time when photosynthesis became a rudimentary process for energy storage in arcane organisms cellular respiration was still to evolve and the energy release mechanism for utilizing the photosynthetic stored energy used processes that sourced their electrons from suppliers other water (Todar, Undated). Later, genetic transfer mechanisms between endosymbiotic bacteria, their closest living relatives being the proteobacteria, and their pre-eukaryotic cellular hosts inducted cell organelles like mitochondria and chloroplasts (Simpson et al, 2002) into the pre-eukaryotic system and cellular respiration became possible. Some time during the endosymbiotic processes there was gene transfer from the bacteria to the pre-eukarytic cells whereby the bacterial genome was reduced and much of the remaining genetic materials got encoded in the cellular nucleus while, locally, some of the bacterial genetic materials were encoded within the organelle, mitochondrion or otherwise, to form localized DNA entirely associated with organelle function (Chihade et al, 2000). ...
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