The Carbon Cycle - GCSE Combined Science Revision - BBC Bitesize

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2. Audio
3. Test

Pages

1. The cycling of materials on Earth
2. The carbon cycle
3. The water cycle

The carbon cycle

Carbon is an essential element for life on Earth. Every living organism has carbon compounds inside each of its cells, such as fats and proteins. The carbon cycle shows how atoms of carbon can exist within different compounds at different times and be recycled between living organisms and the environment.

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Previous imageNext imageSlide 1 of 4, Stage one of the carbon cycle. Overnight, CO2 from burning fuel (combustion) and respiration by cows, birds and plants pass into the atmosphere., Carbon enters the atmosphere as carbon dioxide from respiration and combustion.End of image gallery

Processes in the carbon cycle

The carbon cycle is easiest to understand in terms of its processes and how carbon is converted. The three key processes and the conversions are shown in the table below.

Process	Carbon starts as	Carbon ends as
Photosynthesis	Respiration	Combustion (burning)
Carbon dioxide	Glucose	Fuel (eg methane or wood)
Glucose	Carbon dioxide	Carbon dioxide

Process	Photosynthesis
Carbon starts as	Respiration
Carbon ends as	Combustion (burning)

Process	Carbon dioxide
Carbon starts as	Glucose
Carbon ends as	Fuel (eg methane or wood)

Process	Glucose
Carbon starts as	Carbon dioxide
Carbon ends as	Carbon dioxide

1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
2. Carbon dioxide is absorbed by producers to make glucose in photosynthesis.
3. Animals feed on the plant passing the carbon compounds along the food chain. Most of the carbon they consume is exhaled as carbon dioxide that was formed during aerobic respiration. The animals and plants eventually die.
4. Decomposers break down the dead organisms and return the carbon in their bodies to the atmosphere as carbon dioxide by respiration. In some conditions, decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.

Learn more about the carbon cycle with Dr Alex Lathbridge.

Listen to the full series on BBC Sounds.

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Next pageThe water cyclePrevious pageThe cycling of materials on Earth

More guides on this topic

• Organisation in ecosystems - OCR Gateway

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