Carbon Cycle
Definition and meaning of Carbon Cycle in chemistry.
The carbon cycle is the continuous movement of carbon atoms among the atmosphere, oceans, land, and living organisms, driven by chemical and biological processes such as photosynthesis, respiration, combustion, and dissolution.
In more detail
Carbon moves between reservoirs largely through redox chemistry: photosynthesis reduces atmospheric CO2 into organic carbon compounds, while respiration and combustion oxidize organic carbon back to CO2. In the ocean, CO2 dissolves to form carbonic acid, which equilibrates with bicarbonate and carbonate ions, linking the atmosphere to marine chemistry and to solid carbonate rocks like limestone. Slower geologic processes, including weathering of silicate rocks and volcanic outgassing, exchange carbon with Earth's crust over thousands to millions of years. Human combustion of fossil fuels has significantly accelerated the transfer of long-buried carbon into the atmosphere, raising atmospheric CO2 concentrations.
Key facts
| Field | General Chemistry |
|---|---|
| Key gas species | CO2 (carbon dioxide) |
| Ocean equilibrium species | H2CO3, HCO3-, CO3(2-) |
| Major reservoirs | Atmosphere, oceans, biosphere, soils, fossil fuels, carbonate rocks |
A carbon atom in atmospheric CO2 is fixed by a plant during photosynthesis into glucose; an animal eats the plant and later exhales the carbon back as CO2 through cellular respiration, completing one loop of the cycle.
Frequently asked questions
Is the carbon cycle a chemical or biological process?
Both, it involves biological processes like photosynthesis and respiration as well as purely chemical and geochemical processes like carbonate dissolution, weathering, and combustion.
Why does burning fossil fuels disrupt the carbon cycle?
Fossil fuels store carbon that was removed from the atmosphere over millions of years; burning them releases this carbon as CO2 much faster than natural processes can reabsorb it, increasing atmospheric CO2 levels.