Photosynthesis: The History And History Of Photosynthesis

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 at least two billion years ago, possibly even as long as three [4]. It has been suggested that the process originated not long after the origin of living organisms [3] however free living organisms were the synthesisers, not plants as we know today.

The oldest known photosynthesisers were small aquatic bacteria, such as cyanobacteria and Halobacterium halobium. Biomarkers indicate organisms similar to cyanobacteria were present 2.7 billion years ago [5], and other archaeological fossils have been shown as evidence of photosynthesis at this early stage of Earth’s development. Cyanobacteria, like modern plants, use the energy of the sun to power their photosynthesis, and can photosynthesise in both aerobic and anaerobic conditions. [6] Cyanobacteria were one of the first organisms to produce oxygen. This newly produced oxygen was toxic to a majority of the other species of organism at the time, causing extinction. It was also responsible for the production of an ozone atmosphere [7].

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... and partly fill the need for absorption, and are particularly suited to blue light [8].

Photosynthesis has slowly evolved as a non-linear process. Cyanobacteria hold some of the most responsibility for the process- they allowed for a more oxygenic atmosphere which facilitated the evolution of oxygenic photosystems in land plants. They alone cannot take full credit, and there are many other contributors to modern photosynthesis, from algae to simple pigments such as chlorophyll and bacterial rhodopsin. It has shaped the world around us, from our landscape to the species of animal we see, it could be said to have directly allowed for our own evolution. It can be sure however that it is an extremely successful evolution, a finely tuned process which each photosynthesising species has tailored to its needs, and perhaps may continue to evolve in its efficacy.