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The underlying force driving these reactions is the Gibbs free energy of the reactants relative to the products. If donor and acceptor (the reactants) are of higher free energy than the reaction products, the electron transfer may occur spontaneously. The Gibbs free energy is the energy available ("free") to do work.
In cyclic photophosphorylation, cytochrome b 6 f uses electrons and energy from PSI to create more ATP and to stop the production of NADPH. Cyclic phosphorylation is important to create ATP and maintain NADPH in the right proportion for the light-independent reactions. The net-reaction of all light-dependent reactions in oxygenic photosynthesis ...
Reduced sulfur compounds, such as hydrogen sulfide, elemental sulfur, sulfite, thiosulfate, and various polythionates (e.g., tetrathionate), are oxidized by chemotrophic, phototrophic, and mixotrophic bacteria for energy. [1] Some chemosynthetic archaea use hydrogen sulfide as an energy source for carbon fixation, producing sugars.
In trisomy 21 (Down syndrome) the body produces an excess of hydrogen sulfide. [3] Hydrogen sulfide is also involved in the disease process of type 1 diabetes. The beta cells of the pancreas in type 1 diabetes produce an excess of the gas, leading to the death of these cells and to a reduced production of insulin by those that remain. [5]
Purple sulfur bacteria oxidize hydrogen sulfide (H 2 S) to sulfur (S). In oxygenic photosynthesis, water (H 2 O) serves as a substrate for photolysis resulting in the generation of diatomic oxygen (O 2). This is the process which returns oxygen to Earth's atmosphere.
Hydrogen sulfide is often produced from the microbial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers; this process is commonly known as anaerobic digestion, which is done by sulfate-reducing microorganisms. It also occurs in volcanic gases, natural gas deposits, and sometimes in well-drawn water.
Photosynthesis is the only process that allows the conversion of atmospheric carbon (CO2) to organic (solid) carbon, and this process plays an essential role in climate models. This lead researchers to study the sun-induced chlorophyll fluorescence (i.e., chlorophyll fluorescence that uses the Sun as illumination source; the glow of a plant) as ...
The chemical summation of photosynthesis was a milestone in the understanding of the chemistry of photosynthesis. This was later experimentally verified by Robert Hill. In a nutshell, van Niel proved that plants give off oxygen as a result of splitting water molecules during photosynthesis, not carbon dioxide molecules as thought before.