Photosynthesis Essay

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Photosynthesis uses light energy and carbon dioxide to make triose phospates (G3P). G3P is generally considered the prime end-product of photosynthesis. It can be used as an immediate food nutrient, or combined and rearranged to form disaccharide sugars, such as sucrose and fructose, which can be transported to other cells, or packaged for storage as insoluble polysaccharides such as starch. A commonly used but slightly simplified equation for photosynthesis is: 6 CO2(gas) + 12 H2O(liquid) + photons → C6H12O6(aqueous) + 6 O2(gas) + 6 H2O(liquid) carbon dioxide + water + light energy → glucose + oxygen + water When written as a word equation the light energy appears above the arrow as it is required for photosynthesis but it is not actually a reactant. Here the monosaccharide glucose is shown as a product, although the actual processes in plants produce disaccharides. The equation is often presented in introductory chemistry texts in an even more simplified form as:[2] 6 CO2(gas) + 6 H2O(liquid) + photons → C6H12O6(aqueous) + 6 O2(gas) Photosynthesis occurs in two stages. In the first phase, light-dependent reactions or photosynthetic reactions (also called the Light reactions) capture the energy of light and use it to make high-energy molecules. During the second phase, the light-independent reactions (also called the Calvin-Benson Cycle, and formerly known as the Dark Reactions) use the high-energy molecules to capture carbon dioxide (CO2) and make the precursors of carbohydrates. In the light reactions, one molecule of the pigment chlorophyll absorbs one photon and loses one electron. This electron is passed to a modified form of chlorophyll called pheophytin, which passes the electron to a quinone molecule, allowing the start of a flow of electrons down an electron transport chain that leads to the ultimate reduction of NADP into NADPH. In

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