Compare and Contrast Respiration and Photosynthesis

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Compare and contrast respiration and photosynthesis By MichaeL Notes: Though the processes of respiration and photosynthesis appear to cancel each other out, the fact that some of the carbohydrate remains in the biomass of the plant means that the carbon in this enters other components of the earth system e.g. eaten by animals which decompose and eventually enter the geosphere in some form. Over millions of years, this has built up an imbalance with more oxygen being put into the atmosphere and less carbon dioxide. Some of this geospheric carbon ends up in rocks like limestone or in organic derivatives like coal, oil and gas. Whilst land plants, and rainforests in particular might produce much of the earth’s oxygen through photosynthesis, at least half is produced by the same process in the tiny phytoplankton of the oceans. Respiration Plants and photosynthesising algae and bacteria use some of the carbohydrates they make to release energy for various functions, whilst the rest is used to increase their bulk (biomass), in a process chemically similar to burning. This reaction returns carbon dioxide (CO2) and water (H2O) to the atmosphere as well as releasing energy and can be represented by an equation like the following based on a sugar e.g. glucose Plants get carbon dioxide from the air through their leaves, and water from the ground through their roots. Light energy comes from the sun. The oxygen produced is released into the air from the leaves. The glucose produced can be turned into other substances, such as starch, which is used as a store of energy. This energy can be released by respiration. ** Note that photosynthesis is a reduction-oxidation reaction, just like respiration (see the primer on redox reactions from the lecture on Microbes). In respiration energy is released from sugars when electrons
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