The first photosynthetic organisms probably evolved early in the evolutionary history of life and most likely used reducing agents such as hydrogen or hydrogen sulfide , rather than water, as sources of electrons.
In green plants and algae, photosynthesis takes place in specialized cellular compartments called chloroplasts.
Photosynthesis - New World Encyclopedia
This breakthrough in metabolic evolution greatly increased the free energy supply to living organisms: Chen P-C and Arnon DI Characterization of ferredoxin catalyzed cyclic photophosphorylation under anaerobic conditions. Some bacteria, such as Chromatium, oxidize hydrogen sulfide instead of water, producing sulfur as a waste product. Multicellular life. Skip to main content. Glyco- sphingolipids. Terpenoid Backbones. Two water molecules are oxidized by four successive charge-separation reactions by photosystem II to yield a molecule of diatomic oxygen and four hydrogen ions.
The carbon reduction cycle is known as the Calvin cycle , which ignores the contribution of Bassham and Benson. CAM plants have a different leaf anatomy from C 3 plants, and fix the CO 2 at night, when their stomata are open. Photosynthesis and Photomorphogenesis. Freeman and Company. Evolution of photosynthesis.
Glyco- lysis. Molecular Mechanisms of Photosynthesis 2nd ed. They obtain electrons from a variety of different inorganic chemicals including sulfide or hydrogen ; thus, for most of these bacteria oxygen is not a by-product of photosynthesis. Sexual reproduction. These include phycobilins, which are the red and blue pigments of red and blue algae respectively, and fucoxanthol for brown algae and diatoms. Under these conditions, oxygen gas, produced by the light reactions of photosynthesis, will concentrate in the leaves, causing photorespiration to occur.
It allows the photosynthetic system to try each potential energy pathway simultaneously and choose the most efficient option Berkeley Lab, Biochem Biophys Res Communic This page was last edited on 20 February , at To combat this problem, a series of proteins with different pigments surround the reaction center. Unable to display preview.
Further experiments to prove that the oxygen developed during the photosynthesis of green plants came from water, were performed by Hill in and However, these experiments clearly show that temperature affects the rate of carbon assimilation, so there must be two sets of reactions in the full process of carbon assimilation.
MVA Pathway. Trends Biochem Sci For example, in green plants, the action spectrum resembles the absorption spectrum for chlorophylls and carotenoids with absorption peaks in violet-blue and red light. Plant biology.