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The idea that the oxygen in the atmosphere would "last" for 15,000 years is probably incorrect. When the biosphere experiment was done, the finding was the following: "The oxygen inside the facility, which began at 20.9%, fell at a steady pace and after 16 months was down to 14.5%. This is equivalent to the oxygen availability at an elevation of ...


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The answer above gives a nice calculation how much oxygen there is, and how much we use. There are some BIG other factors that warrant a second answer IMO. Starting at 371 thousand years (above). Animals: according to http://xkcd.com/1338/ (probably sourced somewhere reliable) humans make up only ~20% of the walking biomass, so we would burn through the ...


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Disclaimer: This is going to be a very mathematical answer. Before answering it, I assume that you are only asking about humans, assuming that all other organisms don't require $O_2$ to survive (as it will complicate the answer many many times). List of variables: V = total volume of air on earth (in l) V' = total volume of oxygen on earth (in l) ...


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Can I calculate the estimate through a simple measurement (e.g. of plant weight) or does it require tight lab experiments? In the former case, how is that measurement made? In the textbook Plant Physiological Ecology*, they state that about 40% of the dry weight of plants is carbon, and I believe the vast majority of that is from CO2 from the ...


3

I answered this implicitly in a comment to my answer to: Light and Dark Reaction of photosynthesis?. Anyway: There is no such thing as NADPH2. There is only NADP+ and NADPH. Consult Wikipedia or a reputable text such as Berg. The nicotinamide portion of NADP that undergoes oxidation and reduction is exactly the same as in NAD. The changes undergone are: ...


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You can find two chlorophylls in most plant leaves, chlorophyll a and b. We'll use as a reference Leaf characteristics and chlorophyll concentration of Schyzolobium parahybum and Hymenaea stilbocarpa seedlings grown in different light regimes. The most important observation is that in shade-tolerant leaves, chlorophyll b dominates chlorophyll a. And the ...


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Photosynthesis is the process of trapping sunlight and converting the energy into chemical energy which is then provided as a food source. So the sunlight is trapped through chlorophylls. This is a pigment in the organelle called the chloroplast. The upper surface of the leaf is open to sunlight where the plants have more chloroplasts containing more ...


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But cyanobacteria do not seem to use polysaccharides in the same way as plant cells do (building materials, for example) The Calvin-Benson cycle produces glucose which is the starting material for a lot of biosynthetic pathways including that of the nucleotides (ribose from the pentose-phosphate pathway). Glycolytic intermediates are also involved in ...


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Why do you think that the only benefit from photosynthesis is polysaccharide synthesis? Photosynthesis allows an organism to convert photons into chemical energy. That chemical energy can be stored as polysaccharides and used as a building material, but it can also just be converted into some other compound, or just used to run the organisms metabolism, ...



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