Glyceraldehyde 3-phosphate (G3P)
In a typical leaf, there are two fates for the G3P:
► One-third of it ends up in the polysaccharide starch, which is stored in the chloroplast.
► Two-thirds of it is converted in the cytosol to the disac-charide sucrose, which is transported out of the leaf to other organs in the plant, where it is hydrolyzed to its constituent monosaccharides: glucose and fructose.
The G3P produced in photosynthesis is subsequently used by the plant to make other compounds. Its carbon is thus incorporated into amino acids, lipids, and the building blocks of the nucleic acids.
The products of the Calvin-Benson cycle are of crucial importance to the entire biosphere, for the covalent bonds of the
carbohydrate generated in the cycle represent the total energy yield from the harvesting of light by photosynthetic organisms. Most of this stored energy is released by glycolysis and cellular respiration and used to support plant growth, development, and reproduction. Much plant matter ends up being consumed by animals, supplying them with both raw materials and energy sources. Glycolysis and cellular respiration in the animals release free energy from the plant matter for use in the animal cells.
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