Carbon Cycle (Biology)

Carbon cycle

The biogeochemical process by which carbon is continuously exchanged and recycled among the atmosphere, hydrosphere, geosphere, and biosphere.

Photosynthesis (in the carbon cycle)

The biological process by which green plants and other autotrophs absorb atmospheric $CO_2$ and water to produce glucose and oxygen: $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$.

Cellular respiration (in the carbon cycle)

The metabolic reaction in organisms that oxidizes organic compounds such as glucose, releasing energy along with $CO_2$ back into the atmosphere: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$.

Carbon sink

A natural or artificial reservoir, such as an ocean, peatland, or old-growth forest, that absorbs and accumulates more carbon than it releases.

Carbon source

A process or mechanism, such as fossil fuel combustion, volcanic eruptions, or deforestation, that releases more carbon into the atmosphere than it sequesters.

Decomposition

The breakdown of dead organic material by fungi and bacteria, which enriches soil nutrients and releases $CO_2$ through aerobic respiration or $CH_4$ under anaerobic conditions.

Combustion

The rapid chemical oxidation of organic matter or hydrocarbons in the presence of oxygen, releasing energy, $H_2O$, and $CO_2$ into the atmosphere.