Carbon Cycle
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3/31/2022
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Carbon Cycle – Lithosphere, Biosphere, Hydrosphere & Atmosphere
• Carbon may be stored for
extended periods (sinks):
oceans, sedimentary rock, fossil
fuels, trees
• There are various ways it is
likely to be released to the
atmosphere (sources): burning
of fossil fuels, forest fires,
volcanic activity, weathering of
limestone rock, decomposition
of organic material, respiration
3
3/31/2022
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Carbon Cycle – Humans changing the balance….
Until recently, the environment has maintained a balance in carbon dioxide:
Carbon dioxide is
produced by respiration…
…and used by
photosynthesis
Unfortunately, this balance is being upset by two main factors:
1) Burning of fossil fuels…
…is producing too much carbon dioxide
2) Cutting down trees…
…is slowing down the removal of carbon
dioxide from the atmosphere
What is the photosynthesis reaction?
• The process of photosynthesis
is a chemical reaction
• Word equation:
carbon
+ water  glucose + oxygen
dioxide
• Formula equation:
6CO2 + 6H2O

C6H12O6 + 6O2
Understanding the chemical equation
This means:
6CO2 + 6H2O  C6H12O6 + 6O2
and
makes
and
Where does photosynthesis occur?
Plant leaf
Top of the leaf
Bottom of the
leaf
Where does photosynthesis occur?
Plant leaf
Where does photosynthesis occur?
Plant leaf
Plant cell
Where does photosynthesis occur?
Plant leaf
Plant cell
Chloroplast
Chloroplasts are only found in plants
animal cells
plant cells
That’s why plants are green!
Chloroplasts contain the green pigment chlorophyll
REVIEW : Role of the chloroplasts
• Absorb sunlight
(provides the
energy for the
chemical reaction
of photosynthesis)
sun
• Some of the sugar is used by the plant
O2 +
for energy
• Some is stored in plant tissue
CO2
+
Water
glucose
Why is this important to us?
1. O2 - the oxygen released during photosynthesis
is necessary for breathing (respiratory system)
2. Glucose – we cannot make our own food from
the sunlight, so we must get food from plants,
or animals that eat plants
What is cellular respiration?
• Cellular respiration is the process of using food (glucose) to release
energy
• This process occurs
in all living things!!!
• Plants
• Animals
Where does cellular respiration occur?
• Occurs in organelles called mitochondria
• These are found in both plant and animal cells
animal cells
plant cells
What is the cellular respiration
reaction?
• The process of cellular respiration is a chemical
reaction
• Word equation:
glucose + oxygen  carbon + water
dioxide
• Formula equation:
C6H12O6 + 6O2 
6CO2 + 6H2O
Complementary processes
• Photosynthesis equation:
6CO2 + 6H2O
 C6H12O6 + 6O2
• Cellular respiration equation:
C6H12O6 + 6O2

Cellular respiration is the
OPPOSITE of
photosynthesis
6CO2 + 6H2O
Cellular
Photosynthesis and
cycles
respiration
sun
C6H12O6
H 2O
O2
CO2
Energy is used for
movement,
digestion, growth,
repair and
reproduction.