carbon cycle

(noun)

The physical cycle of carbon through the Earth's biosphere, geosphere, hydrosphere and atmosphere that includes such processes as photosynthesis, decomposition, respiration and carbonification.

Related Terms

Examples of carbon cycle in the following topics:

  • The Carbon Cycle

    • The carbon cycle describes the flow of carbon from the atmosphere to the marine and terrestrial biospheres, and the earth's crust.
    • The carbon cycle describes the flow of carbon between the biosphere, the geosphere, and the atmosphere, and is essential to maintaining life on earth.
    • Marine Biosphere: The carbon cycle in the marine biosphere is very similar to that in the terrestrial ecosystem.
    • The simulation also illustrates differences in carbon dioxide levels in the northern and southern hemispheres and distinct swings in global carbon dioxide concentrations as the growth cycle of plants and trees changes with the seasons.
    • The carbon cycle describes the flow of carbon between the atmosphere, the biosphere, and the geosphere.

  • Sources and Sinks of Essential Elements

    • Ecosystems hinge on biogeochemical cycles.
    • The nitrogen cycle, the phosphorous cycle, the sulfur cycle, and the carbon cycle all involve assimilation of these nutrients into living things.
    • Coal is a reservoir for carbon, and coal deposits can house carbon for thousands of years.
    • For example, coal is a resevoir of carbon, but the human use of fossil fuels has released carbon into the atmosphere, increasing the amount of carbon in circulation.
    • The element carbon moves from the biosphere to the geosphere and the hydrosphere.

  • The Reverse TCA Cycle

    • The reverse TCA cycle utilizes carbon dioxide and water to form carbon compounds.
    • The citric acid cycle (TCA) or Krebs cycle, is a process utilized by numerous organisms to generate energy via the oxidation of acetate derived from carbohydrates, fats, and proteins into carbon dioxide .
    • This process is characterized by the production of carbon compounds from carbon dioxide and water.
    • The reverse TCA cycle is a series of chemical reactions by which organisms produce carbon compounds from carbon dioxide and water.
    • Reverse TCA, a form of carbon fixation, utilizes numerous ATP molecules, hydrogen and carbon dioxide to generate an acetyl CoA.

  • The 3-Hydroxypropionate Cycle

    • The 3-hydroxypropionate cycle is a carbon fixation pathway that results in the production of acetyl-CoA and glyoxylate.
    • One of the pathways that is utilized for carbon fixation is the 3-hydroxypropionate cycle.
    • Specifically, in this cycle, the carbon dioxide is fixed by acetyl-CoA and propionyl-CoA carboxylases.
    • However, the cycle can be broken down into two major phases, carbon dioxide fixation and glyoxylate assimilation.
    • Recall the two major phases and known steps in the 3-hydroxypropionate cycle

  • Intermediates Produced During the Calvin Cycle

    • The Calvin Cycle involves the process of carbon fixation to produce organic compounds necessary for metabolic processes.
    • The Calvin Cycle is characterized as a carbon fixation pathway.
    • The Calvin cycle is most often associated with carbon fixation in autotrophic organisms, such as plants, and is recognized as a dark reaction.
    • In organisms that require carbon fixation, the Calvin cycle is a means to obtain energy and necessary components for growth.
    • The GAP molecules at this point are the end product of the Calvin cycle, which is responsible for reducing carbon to a sugar form.

  • Regulation of the Calvin Cycle

    • The Calvin cycle is a process that ensures carbon dioxide fixation in plants.
    • The Calvin cycle is a process utilized to ensure carbon dioxide fixation.
    • During the first phase of the Calvin cycle, carbon fixation occurs.
    • The regulation of the Calvin cycle requires many key enzymes to ensure proper carbon fixation.
    • Outline the three major phases of the Calvin cycle: carbon fixation, reduction, and regeneration of ribulose

  • Acetyl CoA and the Citric Acid Cycle

    • The citric acid cycle, shown in —also known as the tricarboxylic acid cycle (TCA cycle) or the Krebs cycle—is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate—derived from carbohydrates, fats, and proteins—into carbon dioxide.
    • The cycle consumes acetate (in the form of acetyl-CoA) and water, reduces NAD+ to NADH, and produces carbon dioxide.
    • Through the catabolism of sugars, fats, and proteins, a two carbon organic product acetate in the form of acetyl-CoA is produced.
    • Acetyl-CoA along with two equivalents of water (H2O) are consumed by the citric acid cycle, producing two equivalents of carbon dioxide (CO2) and one equivalent of HS-CoA.
    • The citric acid cycle, or Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidization of acetate—derived from carbohydrates, fats, and proteins—into carbon dioxide.

  • Biosynthesis and Energy

    • Carbon dioxide fixation is necessary to ensure carbon dioxide can be converted into organic carbon.
    • The major pathways utilized to ensure fixation of carbon dioxide include: the Calvin cycle, the reductive TCA cycle, and the acetyl-CoA pathway.
    • The Calvin cycle involves utilizing carbon dioxide and water to form organic compounds.
    • The reductive TCA cycle, commonly referred to as the reverse Krebs cycle, also produces carbon compounds from carbon dioxide and water.
    • In the acetyl-CoA pathway, carbon dioxide is reduced to carbon monoxide and then acetyl-CoA.

  • Role of Microbes in Biogeochemical Cycling

    • Nutrients move through the ecosystem in biogeochemical cycles.
    • A biogeochemical cycle is a pathway by which a chemical element (such as carbon or nitrogen) circulates through the biotic (living) and the abiotic (non-living) factors of an ecosystem.
    • A good example of a molecule that is cycled within an ecosystem is water, which is always recycled through the water cycle.
    • The key collective metabolic processes of microbes (including nitrogen fixation, carbon fixation, methane metabolism, and sulfur metabolism) effectively control global biogeochemical cycling.
    • The transformative process by which carbon dioxide is taken up from the atmospheric reservoir and "fixed" into organic substances is called carbon fixation.

  • The Acetyl-CoA Pathway

    • Acetyl-CoA is a major component in numerous metabolic processes as it plays a key role in the citric acid cycle.
    • The main function of acetyl-CoA in the citric cycle is to transport carbon atoms.
    • The acetyl-CoA pathway begins with the reduction of a carbon dioxide to carbon monoxide.
    • The carbon monoxide dehydrogenase allows organisms to use carbon dioxide as a source of carbon and carbon monoxide as a source of energy.The carbon monoxide dehydrogenase can also form a complex with the acetyl-CoA synthase complex which is key in the acetyl-CoA pathway.
    • Acetogens are able to use carbon dioxide as a source of carbon and hydrogen as a source of energy.