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The cycles of synthesis and degradation of ATP; 2 and 1 represent input and output of energy, respectively. ATP is stable in aqueous solutions between pH 6.8 and 7.4 (in the absence of catalysts). At more extreme pH levels, it rapidly hydrolyses to ADP and phosphate. Living cells maintain the ratio of ATP to ADP at a point ten orders of ...
This will provide a potential energy difference between lumen and stroma, which amounts to a proton-motive force that can be utilized by the proton-driven ATP synthase to generate ATP. If electrons only pass through once, the process is termed noncyclic photophosphorylation, but if they pass through PSI and the proton pump multiple times it is ...
The energy derived from the pumping of protons across a cell membrane is frequently used as the energy source in secondary active transport. In humans, sodium (Na + ) is a commonly cotransported ion across the plasma membrane, whose electrochemical gradient is then used to power the active transport of a second ion or molecule against its ...
By replenishing lost electrons with electrons from the splitting of water, photosystem II provides the electrons for all of photosynthesis to occur. The hydrogen ions (protons) generated by the oxidation of water help to create a proton gradient that is used by ATP synthase to generate ATP .
The fact that a reaction is thermodynamically possible does not mean that it will actually occur. A mixture of hydrogen gas and oxygen gas does not spontaneously ignite. It is necessary either to supply an activation energy or to lower the intrinsic activation energy of the system, in order to make most biochemical reactions proceed at a useful ...
Ultimately, the electrons that are transferred by Photosystem I are used to produce the moderate-energy hydrogen carrier NADPH. [2] The photon energy absorbed by Photosystem I also produces a proton-motive force that is used to generate ATP. PSI is composed of more than 110 cofactors, significantly more than Photosystem II. [3]
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These regulatory functions prevent the Calvin cycle from being respired to carbon dioxide. Energy (in the form of ATP) would be wasted in carrying out these reactions when they have no net productivity. [citation needed] The sum of reactions in the Calvin cycle is the following: [citation needed] 3 CO 2 + 6 NADPH + 9 ATP + 5 H