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  2. Cellular respiration - Wikipedia

    en.wikipedia.org/wiki/Cellular_respiration

    Nutrients that are commonly used by animal and plant cells in respiration include sugar, amino acids and fatty acids, and the most common oxidizing agent is molecular oxygen (O 2). The chemical energy stored in ATP (the bond of its third phosphate group to the rest of the molecule can be broken allowing more stable products to form, thereby ...

  3. Photosynthesis - Wikipedia

    en.wikipedia.org/wiki/Photosynthesis

    To use this stored chemical energy, an organism's cells metabolize the organic compounds through cellular respiration. Photosynthesis plays a critical role in producing and maintaining the oxygen content of the Earth's atmosphere, and it supplies most of the biological energy necessary for complex life on Earth. [2]

  4. Oxygen cycle - Wikipedia

    en.wikipedia.org/wiki/Oxygen_cycle

    The Earth's atmosphere, hydrosphere, and biosphere together hold less than 0.05% of the Earth's total mass of oxygen. Besides O 2, additional oxygen atoms are present in various forms spread throughout the surface reservoirs in the molecules of biomass, H 2 O, CO 2, HNO 3, NO, NO 2, CO, H 2 O 2, O 3, SO 2, H 2 SO 4, MgO, CaO, Al2O3, SiO 2, and ...

  5. Oxygen evolution - Wikipedia

    en.wikipedia.org/wiki/Oxygen_evolution

    Oxygen evolution is the chemical process of generating elemental diatomic oxygen (O 2) by a chemical reaction, usually from water, the most abundant oxide compound in the universe. Oxygen evolution on Earth is effected by biotic oxygenic photosynthesis , photodissociation , hydroelectrolysis , and thermal decomposition of various oxides and ...

  6. Respiration (physiology) - Wikipedia

    en.wikipedia.org/wiki/Respiration_(physiology)

    The process of breathing does not fill the alveoli with atmospheric air during each inhalation (about 350 ml per breath), but the inhaled air is carefully diluted and thoroughly mixed with a large volume of gas (about 2.5 liters in adult humans) known as the functional residual capacity which remains in the lungs after each exhalation, and ...

  7. Oxygen - Wikipedia

    en.wikipedia.org/wiki/Oxygen

    Oxygen is the most abundant chemical element by mass in the Earth's biosphere, air, sea and land. Oxygen is the third most abundant chemical element in the universe, after hydrogen and helium. [ 68 ] About 0.9% of the Sun 's mass is oxygen. [ 19 ]

  8. Autotroph - Wikipedia

    en.wikipedia.org/wiki/Autotroph

    This is the main way that primary producers get energy and make it available to other forms of life. Plants, many corals (by means of intracellular algae), some bacteria (cyanobacteria), and algae do this. During photosynthesis, primary producers receive energy from the sun and use it to produce sugar and oxygen.

  9. Evolution of photosynthesis - Wikipedia

    en.wikipedia.org/wiki/Evolution_of_photosynthesis

    Earth forms 3.4 billion years ago First photosynthetic bacteria appear 2.7 billion years ago Cyanobacteria become the first oxygen producers 2.4 – 2.3 billion years ago Earliest evidence (from rocks) that oxygen was in the atmosphere 1.2 billion years ago Red and brown algae become structurally more complex than bacteria 0.75 billion years ago