12/11/2023 0 Comments Charge of carbon dioxide![]() Cyanobacteria appeared later the excess oxygen they produced contributed directly to the oxygenation of the Earth, which rendered the evolution of complex life possible. 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 other bacteria, different mechanisms such as the reverse Krebs cycle are used to achieve the same end. ![]() Using the ATP and NADPH produced by the light-dependent reactions, the resulting compounds are then reduced and removed to form further carbohydrates, such as glucose. In the Calvin cycle, atmospheric carbon dioxide is incorporated into already existing organic carbon compounds, such as ribulose bisphosphate (RuBP). In plants, algae and cyanobacteria, sugars are synthesized by a subsequent sequence of light-independent reactions called the Calvin cycle. The hydrogen freed by the splitting of water is used in the creation of two further compounds that serve as short-term stores of energy, enabling its transfer to drive other reactions: these compounds are reduced nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine triphosphate (ATP), the "energy currency" of cells. ![]() In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. In plants, these proteins are chlorophyll (a porphyrin derivative that absorbs the red and blue spectrums of light, thus reflecting a green color) held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane. Such archaeal photosynthesis might have been the earliest form of photosynthesis evolved on Earth, going back as far as the Paleoarchean, preceding that of cyanobacteria (see Purple Earth hypothesis).Īlthough photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centers that contain photosynthetic pigments or chromophores. ![]() Archaea such as Halobacterium also perform a type of non- carbon-fixing anoxygenic photosynthesis, where the simpler photopigment retinal and its microbial rhodopsin derivatives are used to absorb green light and power proton pumps to directly synthesize adenosine triphosphate (ATP). Some bacteria also perform anoxygenic photosynthesis, which use bacteriochlorophyll to split hydrogen sulfide as a reductant instead of water, and sulfur is produced as a byproduct instead of oxygen. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies most of the biological energy necessary for complex life on Earth. Most plants, algae and cyanobacteria perform photosynthesis such organisms are called photoautotrophs. The term usually refers to oxygenic photosynthesis, where oxygen is produced as a byproduct, and some of the chemical energy produced is stored in carbohydrate molecules such as sugars, starch, glycogen and cellulose, which are synthesized from endergonic reaction of carbon dioxide with water. Photosynthesis ( / ˌ f oʊ t ə ˈ s ɪ n θ ə s ɪ s/ FOH-tə- SINTH-ə-sis) is a biological process used by many cellular organisms to convert light energy into chemical energy, which is stored in organic compounds that can later be metabolized through cellular respiration to fuel the organism's activities. Dark red and blue-green indicate regions of high photosynthetic activity in the ocean and on land, respectively. Composite image showing the global distribution of photosynthesis, including both oceanic phytoplankton and terrestrial vegetation. The carbohydrates produced are stored in or used by the plant. Biological process to convert light into chemical energy
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