carbon cycle

Examples of carbon cycle in the following topics:

• The Carbon Cycle

• The Carbon Cycle

  • Carbon enters the atmosphere in the form of carbon dioxide via the carbon cycle and returns to organic carbon via photosynthesis.
  • The carbon cycle is most easily studied as two interconnected sub-cycles: one dealing with rapid carbon exchange among living organisms and the other dealing with the long-term cycling of carbon through geologic processes .
  • The movement of carbon through the land, water, and air is complex and, in many cases, it occurs much more slowly than the biological carbon cycle.
  • Photosynthesis converts carbon dioxide gas to organic carbon, while respiration cycles the organic carbon back into carbon dioxide gas.
  • Volcanic activity and human emissions bring this stored carbon back into the carbon cycle.

• 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.

• The Chemical Basis for Life

  • On earth, carbon circulates through the land, ocean, and atmosphere, creating what is known as the Carbon Cycle.
  • This global carbon cycle can be divided further into two separate cycles: the geological carbon cycles takes place over millions of years, whereas the biological or physical carbon cycle takes place from days to thousands of years.
  • In a nonliving environment, carbon can exist as carbon dioxide (CO2), carbonate rocks, coal, petroleum, natural gas, and dead organic matter.
  • The fundamental component for all of these macromolecules is carbon.
  • All living things contain carbon in some form, and carbon is the primary component of macromolecules, including proteins, lipids, nucleic acids, and carbohydrates.

• 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.

• Acetyl CoA to CO2

  • The acetyl carbons of acetyl CoA are released as carbon dioxide in the citric acid cycle.
  • In the citric acid cycle, the two carbons that were originally the acetyl group of acetyl CoA are released as carbon dioxide, one of the major products of cellular respiration, through a series of enzymatic reactions .
  • For each acetyl CoA that enters the citric acid cycle, two carbon dioxide molecules are released in reactions that are coupled with the production of NADH molecules from the reduction of NAD+ molecules.
  • For each molecule of acetyl CoA that enters the citric acid cycle, two carbon dioxide molecules are released, removing the carbons from the acetyl group.
  • Describe the fate of the acetyl CoA carbons in the citric acid cycle

• 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.

• 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.

• Citric Acid Cycle

  • The citric acid cycle is a series of reactions that produces two carbon dioxide molecules, one GTP/ATP, and reduced forms of NADH and FADH2.
  • Two carbon atoms come into the citric acid cycle from each acetyl group, representing four out of the six carbons of one glucose molecule.
  • Two carbon dioxide molecules are released on each turn of the cycle; however, these do not necessarily contain the most recently-added carbon atoms.
  • The two acetyl carbon atoms will eventually be released on later turns of the cycle; thus, all six carbon atoms from the original glucose molecule are eventually incorporated into carbon dioxide.
  • In the citric acid cycle, the acetyl group from acetyl CoA is attached to a four-carbon oxaloacetate molecule to form a six-carbon citrate molecule.

• Properties of Carbon

  • Allotropes of carbon are not limited to diamond and graphite, but also include buckyballs (fullerenes), amorphous carbon, glassy carbon, carbon nanofoam, nanotubes, and others.
  • Carbon compounds form the basis of all known life on Earth, and the carbon-nitrogen cycle provides some energy produced by the sun and other stars.
  • Carbon has two stable, naturally occurring isotopes: carbon-12 and carbon-13.
  • Carbon-12 makes 98.93% and carbon-13 forms the remaining 1.07%.
  • Some allotropes of carbon: a) diamond, b) graphite, c) lonsdaleite, d–f) fullerenes (C60, C540, C70); g) amorphous carbon, h) carbon nanotube.