In plants, occur in the of the and use light energy to synthesize ATP and NADPH. The light-dependent reaction has two forms: cyclic and non-cyclic. In the non-cyclic reaction, the are captured in the light-harvesting of by and other (see diagram at right). When a chlorophyll molecule at the core of the photosystem II reaction center obtains sufficient excitation energy from the adjacent antenna pigments, an electron is transferred to the primary electron-acceptor molecule, pheophytin, through a process called . These electrons are shuttled through an , the so-called shown in the diagram, that initially functions to generate a across the membrane. An enzyme uses the chemiosmotic potential to make ATP during photophosphorylation, whereas is a product of the terminal reaction in the . The electron enters a chlorophyll molecule in . The electron is excited due to the light absorbed by the . A second electron carrier accepts the electron, which again is passed down lowering energies of . The energy created by the electron acceptors is used to move hydrogen ions across the thylakoid membrane into the lumen. The electron is used to reduce the co-enzyme NADP, which has functions in the light-independent reaction. The cyclic reaction is similar to that of the non-cyclic, but differs in the form that it generates only ATP, and no reduced NADP (NADPH) is created. The cyclic reaction takes place only at photosystem I. Once the electron is displaced from the photosystem, the electron is passed down the electron acceptor molecules and returns to photosystem I, from where it was emitted, hence the name .
A. Some parasitic plants lack chlorophyll entirely and steal the products of photosynthesis from their green hosts, said Susan K. Pell, director of science at the Brooklyn Botanic Garden. Other plants, like a red-leafed tree, have plenty of chlorophyll, but the molecule is masked by another pigment.
Are plants using green light for photosynthesis
In the or dark reactions the captures from the and in a process that requires the newly formed NADPH, called the Calvin-Benson Cycle, releases three-carbon sugars, which are later combined to form sucrose and starch. The overall equation for the light-independent reactions in green plants is:
Plant - Simple English Wikipedia, the free encyclopedia
The biochemical capacity to use water as the source for electrons in photosynthesis evolved once, in a of extant . The geological record indicates that this transforming event took place early in Earth's history, at least 2450–2320 million years ago (Ma), and, it is speculated, much earlier. Available evidence from geobiological studies of (>2500 Ma) indicates that life existed 3500 Ma, but the question of when oxygenic photosynthesis evolved is still unanswered. A clear paleontological window on cyanobacterial opened about 2000 Ma, revealing an already-diverse biota of blue-greens. remained principal throughout the (2500–543 Ma), in part because the redox structure of the oceans favored photoautotrophs capable of . joined blue-greens as major primary producers on near the end of the , but only with the (251–65 Ma) radiations of dinoflagellates, coccolithophorids, and diatoms did in marine shelf waters take modern form. Cyanobacteria remain critical to as primary producers in oceanic gyres, as agents of biological nitrogen fixation, and, in modified form, as the of marine algae.
Plant - definition of plant by The Free Dictionary
Photosynthesis definition, the complex process by which carbon dioxide, water, and certain inorganic salts are converted into carbohydrates by green plants, algae. photsynthesis in plants
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In 1796, , a Swiss pastor, botanist, and naturalist, demonstrated that green plants consume carbon dioxide and release oxygen under the influence of light. Soon afterward, showed that the increase in mass of the plant as it grows could not be due only to uptake of CO2 but also to the incorporation of water. Thus, the basic reaction by which photosynthesis is used to produce food (such as glucose) was outlined.