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The oxygen cycle is the biogeochemical cycle of oxygen atoms between different oxidation states in ions, oxides, and molecules through redox reactions within and between the spheres/reservoirs of the planet Earth. [1] The word oxygen in the literature typically refers to the most common oxygen allotrope, elemental/diatomic oxygen (O 2 ), as it ...
Photorespiration (also known as the oxidative photosynthetic carbon cycle or C2 cycle) refers to a process in plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. The desired reaction is the addition of carbon dioxide to RuBP ( carboxylation ), a key step in the Calvin–Benson cycle ...
Photosynthesis ( / ˌfoʊtəˈsɪnθəsɪs / FOH-tə-SINTH-ə-sis) [1] is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their activities.
Phototroph. Phototrophs (from Ancient Greek φῶς, φωτός (phôs, phōtós) 'light', and τροφή (trophḗ) 'nourishment') are organisms that carry out photon capture to produce complex organic compounds (e.g. carbohydrates) and acquire energy. They use the energy from light to carry out various cellular metabolic processes.
Geological history of oxygen. O build-up in the Earth's atmosphere. Red and green lines represent the range of the estimates while time is measured in billions of years ago ( Ga ). Stage 1 (3.85–2.45 Ga): Practically no O in the atmosphere. Stage 2 (2.45–1.85 Ga): O produced, but absorbed in oceans and seabed rock.
Photoheterotroph. Photoheterotrophs ( Gk: photo = light, hetero = (an)other, troph = nourishment) are heterotrophic phototrophs —that is, they are organisms that use light for energy, but cannot use carbon dioxide as their sole carbon source. Consequently, they use organic compounds from the environment to satisfy their carbon requirements ...
Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae, and cyanobacteria. Within the photosystem, enzymes capture photons of light to energize electrons that are then transferred through a variety ...
Evolution of photosynthesis. The evolution of photosynthesis refers to the origin and subsequent evolution of photosynthesis, the process by which light energy is used to assemble sugars from carbon dioxide and a hydrogen and electron source such as water. It is believed that the pigments used for photosynthesis initially were used for ...