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Glycolysis is the metabolic pathway that converts glucose (C 6 H 12 O 6) into pyruvate and, in most organisms, occurs in the liquid part of cells (the cytosol). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH). [ 1 ]
Cellular respiration is a vital process that occurs in the cells of all [[plants and some bacteria ]]. [2] [better source needed] Respiration can be either aerobic, requiring oxygen, or anaerobic; some organisms can switch between aerobic and anaerobic respiration. [3] [better source needed]
Like glycolysis, the pentose phosphate pathway appears to have a very ancient evolutionary origin. The reactions of this pathway are mostly enzyme catalyzed in modern cells, however, they also occur non-enzymatically under conditions that replicate those of the Archean ocean, and are catalyzed by metal ions, particularly ferrous ions (Fe(II)). [5]
All cells can perform anaerobic respiration by glycolysis. Additionally, most organisms can perform more efficient aerobic respiration through the citric acid cycle and oxidative phosphorylation . Additionally plants , algae and cyanobacteria are able to use sunlight to anabolically synthesize compounds from non-living matter by photosynthesis .
Major metabolic pathways that occur in the cytosol in animals are protein biosynthesis, the pentose phosphate pathway, glycolysis and gluconeogenesis. [66] The localization of pathways can be different in other organisms, for instance fatty acid synthesis occurs in chloroplasts in plants [67] [68] and in apicoplasts in apicomplexa. [69]
When animals and fungi consume plants, they use cellular respiration to break down these stored carbohydrates to make energy available to cells. [2] Both animals and plants temporarily store the released energy in the form of high-energy molecules, such as adenosine triphosphate (ATP), for use in various cellular processes. [3]
In vertebrates, gluconeogenesis occurs mainly in the liver and, to a lesser extent, in the cortex of the kidneys. It is one of two primary mechanisms – the other being degradation of glycogen ( glycogenolysis ) – used by humans and many other animals to maintain blood sugar levels , avoiding low levels ( hypoglycemia ). [ 2 ]
It occurs in ten steps and proves that phosphorylation is a much required and necessary step to attain the end products. Phosphorylation initiates the reaction in step 1 of the preparatory step [ 5 ] (first half of glycolysis), and initiates step 6 of payoff phase (second phase of glycolysis).