Search results
Results from the WOW.Com Content Network
Photosynthesis occurs in two stages. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the hydrogen carrier NADPH and the energy-storage molecule ATP. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide.
The chemical energy stored in ATP (the bond of its third phosphate group to the rest of the molecule can be broken allowing more stable products to form, thereby releasing energy for use by the cell) can then be used to drive processes requiring energy, including biosynthesis, locomotion or transportation of molecules across cell membranes.
All organisms produce a phosphate compound, ATP, which is the universal energy currency of life. In photophosphorylation, light energy is used to pump protons across a biological membrane, mediated by flow of electrons through an electron transport chain. This stores energy in a proton gradient.
Chemiosmotic coupling between the energy of sunlight, bacteriorhodopsin and phosphorylation (chemical energy) during photosynthesis in the halophilic archaeal organism Halobacterium salinarum (syn. H. halobium). The archaeal cell wall is omitted. [6] [7] Bacteria and archaea also can use chemiosmosis to generate ATP.
The energy used by human cells in an adult requires the hydrolysis of 100 to 150 mol/L of ATP daily, which means a human will typically use their body weight worth of ATP over the course of the day. [30] Each equivalent of ATP is recycled 1000–1500 times during a single day (150 / 0.1 = 1500), [29] at approximately 9×10 20 molecules/s. [29]
Photosynthesis is the main means by which plants, algae and many bacteria produce organic compounds and oxygen from carbon dioxide and water (green arrow). An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms.
The resulting proton gradient across the thylakoid membrane creates a proton-motive force, used by ATP synthase to form ATP. In cyclic photophosphorylation, cytochrome b 6 f uses electrons and energy from PSI to create more ATP and to stop the production of NADPH.
During the first phase, it requires the breakdown of two ATP molecules. [1] During the second phase, chemical energy from the intermediates is transferred into ATP and NADH. [2] The breakdown of one molecule of glucose results in two molecules of pyruvate, which can be further oxidized to access more energy in later processes. [1]