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| Pentose Phosphate Pathway |
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| In some microorganisms, biological oxidation of glucose follows a different pathway. It is known as pentose phosphate pathway or hexose mono phosphate shunt or direct oxidation of glucose. |
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| Pentose Phosphate Pathway |
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| In pentose pathway, glucose-6-phosphate produced during the early stages of glycolysis are oxidised to give rise to 6-phosphogluconate. This reaction takes place in the presence of the enzyme, glucose-6-phosphate dehydrogenase, and generates NADPH. The 6-phosphogluconate molecule is further oxidised by the enzyme 6-phospho gluconate dehydrogenase. |
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| As a result of this, one molecule each of ribulose-5-phosphate, carbon dioxide and NADPH are produced. Ribulose 5 phosphate undergoes many changes to produce glycolytic intermediate such as glyceraldehydes-3-phosphate and fructose-6-phosphate. |
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| The HMP pathway is not only an energy providing process, but it is an important source of many intermediates for synthetic pathway as well. |
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| Localisation of cellular respiration |
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| a) Glycolysis occurs in the cytoplasm. |
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| b) Kreb's cycle and oxidative phosphorylation in the mito chondrion and hyrolysis of ATP at the sites of the biological activity. |
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| c) The reactions of hexose-mono phosphate pathway and activation of pyruvic acid to produce acetyl CoA take place in cytoplasm or on the outer membrane of the mito chondrion. |
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| The cristae in mitochondria are responsible for electron transport system together with the synthesis of ATP. |
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| ATP molecules synthesised in the mitochondria are gradually released into the cytoplasm. Here ATP molecules may be hydrolysed and the energy released is utilised for various biological reactions. It is for this reason that cells actively engaged in energy consuming processes normally contain a large number of mitochondria. |
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