The carbon cycle

In a nutshell

The carbon cycle is the process in which carbon is recycled on Earth. There are a variety of processes, which release or take in carbon from the environment. Naturally-occurring biological processes and human activity contribute to the carbon cycle.

Release of carbon into the atmosphere

The compound carbon dioxide ($$CO_2$$) contains carbon and is the main component of the carbon cycle. Carbon, in the form of $$CO_2$$​, is released into the atmosphere when:

• Organisms respire
• Dead matter or waste is decomposed by respiring microorganisms 
• Fossil fuels are burned (human activity)
  
  

Tip: all organisms respire to release energy; the word equation for aerobic (with oxygen) respiration is: 

​$$glucose+oxygen \rightarrow carbon ~dioxide + water \\ \ \\ C_6H_{12}O_6+O_2+ 6CO_2 + 6H_2O$$​​

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Role of photosynthesis in the carbon cycle 

Photosynthesis is a process in which plants convert light energy from the sun into chemical energy in the form of sugars. Photosynthesis occurs in the chloroplasts of plant cells. Light energy from the sun is used to convert carbon dioxide from the atmosphere into oxygen and glucose.

The equation for photosynthesis is:

​$$carbon ~ dioxide + water \rightarrow glucose + oxygen \\ \ \\ 6CO_2 + 6H_2O\rightarrow C_6H_{12}O_6+O_2$$

The carbon cycle

The process by which carbon on Earth is recycled is described below.