The carbon cycle
It is reasonably likely that you have some carbon atoms in your body that were once inside Charles Darwin or Marie Curie or any other long dead individual. Atoms exist in different forms or A substance formed by the chemical union of two or more elements. at different times in history and cycle between them.
Carbon is an essential A substance made of one type of atom only. for life on Earth and parts of the cells in our bodies, including carbohydrates, proteins, lipids and DNA, are made from it. The carbon cycle shows how atoms of this element can exist within different compounds, at different times.
Image caption, Stage one of the carbon cycle
Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
1 of 4
The The processes and events involved in recycling carbon in the environment. is easiest to understand in terms of its processes and the conversion of carbon that they undertake. The three key processes and their conversions are shown in the table below.
| Process | Carbon starts as | Carbon ends as |
| Photosynthesis | Carbon dioxide | Glucose |
| Respiration | Glucose | Carbon dioxide |
| Combustion (burning) | Fuel (eg methane or wood) | Carbon dioxide |
| Process | Photosynthesis |
|---|---|
| Carbon starts as | Carbon dioxide |
| Carbon ends as | Glucose |
| Process | Respiration |
|---|---|
| Carbon starts as | Glucose |
| Carbon ends as | Carbon dioxide |
| Process | Combustion (burning) |
|---|---|
| Carbon starts as | Fuel (eg methane or wood) |
| Carbon ends as | Carbon dioxide |
More guides on this topic
- What happens during photosynthesis? - OCR 21st Century
- How do producers get the substances they need? - OCR 21st Century
- How do producers transport substances they need? - OCR 21st Century
- How are organisms in an ecosystem interdependent? - OCR 21st Century
- How are populations affected by conditions in an ecosystem?
- Sample exam questions - living together - OCR 21st Century