Carbon and the Carbon cycle
The element carbon is a basic constituent of all living organisms. Its atoms combine easily with other
atoms to form a huge variety of molecules. Some of these (___________________,
____________________) have names which make it obvious they are carbon-based, while others (
_____________, ______________)you just have to remember.
All cells - whether animal, plant or bacteria - contain carbon because they all contain proteins, fats and
carbohydrates. Plant cell walls for example are made of cellulose, a carbohydrate.
Living organisms need carbon in order to:

___________________:Green plants get their carbon from the carbon dioxide in the air, which
enters the leaves and is used for _________________________. A product of photosynthesis is
glucose - another carbon-based compound.

____________________: In ____________________ glucose reacts with oxygen to produce
energy (with carbon dioxide as a by-product).

______________________________________: Carbon compounds are essential cellular
building-blocks.
The Carbon Cycle
Carbon cycles through ecosystems, moving repeatedly from one organism to another, and between
organisms and the environment. The carbon cycle is a key factor in maintaining the balance of an
ecosystem. It works like this:
1.
2.
3.
4.
5.
6.
FUELS COMBUSTION
RESPIRATION
ANIMAL RESPIRATION
PHOTOSYNTHESIS
DISSOLVING
PLANT
1. Write down three ways in which carbon dioxide is put into the
a.
b.
c.
2. Write down two ways that carbon dioxide is removed from the atmosphere
a.
b.
3. The amount of carbon dioxide in the atmosphere does not change very much because it is being taken
out of the atmosphere at ________________ ( a higher / the same / a lower) rate as it is being added.
4. Over the last century, more and more fossil fuels have been burnt. This causes more carbon dioxide to
be released into the atmosphere. Despite this, the amount of carbon dioxide in the atmosphere has not
gone up very much. This is helped by the fact that so much of the Earth’s surface is covered in water.
Explain the importance of the oceans in helping to keep the carbon dioxide level in the atmosphere at a
low level.