Photosynthesis is a series of light driven reactions that convert energy poor compounds such as

1200 WordsApr 23, 20195 Pages
Photosynthesis is a series of light driven reactions that convert energy poor compounds such as carbon dioxide and water to energy rich sugars [1] such as glucose. The process generate an electron gradient across the membrane of a chloroplast, which is used for ATP synthesis, and simultaneously produces electrons used to make NADPH, using NADP+ as an energy carrier[2]. Crudely put, it is the method by which autotrophic plants make their own ‘food.’ All eukaryotic plant cells that have coloured plastids contain their photosynthetic pigments in these membrane bound units [3]. In land plants, the facilitators of photosynthesis are the chloroplasts. Photosynthesis is not a young process- there is evidence that algal photosynthesis existed…show more content…
The first endosymbiotic event involved the engulfing of an alpha proteo bacterium by a proto-eukaryote, giving rise to the presence of mitochondria in cells. Chloroplasts developed from cyanobacteria. After this first endosymbiotic event which led to the evolution of cells to incorporate mitochondria, there was an endosymbiotic event which led to the engulfing of cyanobacteria by eukaryotic cells [8]. Fig. 2 The majority of original cyanobacteria genes have been lost, however there was enough distinctness in the genetic construction of chloroplasts to indicate an extracellular origin to researchers [3]. For example a chloroplast membrane, coded by the gene Toc75, has a homolog in cyanobacteria (SynToc75). In chloroplasts, the protein helps to import other proteins from the cytoplasm to the chloroplast. In cyanobacteria, the function is not full elucidated, however knockout mutations prove fatal indicating it is an essential protein [10]. This theory provides an explanation for the double membrane of chloroplasts. Permanent lineages being transferred, such as the cyanobacteria, require gene transfer to the host, which can incur the loss of extensive genetic information. Gene loss occurs during the addition of chloroplasts from eukaryotic sources but a variation is seen between different lineages. Chloroplasts have fewer genes than their free - living relatives. One of the most significant barriers to gene
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