Oxygen makes up 21% of the atmosphere and is used by all living things through respiration and photosynthesis. During respiration, glucose and oxygen are used to produce energy, carbon dioxide, and water. In photosynthesis, plants use carbon dioxide, water, and sunlight to produce oxygen and glucose. This cycle of oxygen production and consumption between organisms through respiration and photosynthesis is essential for life.

1. THE OXYGEN CYCLE

2. OXYGEN
is a colorless gas that makes up 21
percent of Earth's atmosphere. Because
it's all around, oxygen is easy to dismiss
as dull and inert; in fact, it's the most
reactive of the non-metallic elements.
O! I am OXYGEN!

3. All living things use oxygen or depend on organisms
that use oxygen in some way.

4. We use oxygen to break down simple sugar and release energy. This
can be done through respiration or fermentation.

5. Animals mainly use respiration too.

6. WHAT IS RESPIRATION?
It occurs inside the cell. The process that
breaks apart molecules to release
energy.
It is What YOU do with the oxygen you
take in.

7. We break down food into smaller
molecules during digestion. One of the
small molecules is glucose.
Glucose leaves your intestines, goes into
your blood and is taken to every cell in
your body

8. We break down food into smaller
molecules during digestion. One of the
small molecules is glucose.
Glucose leaves your intestines, goes into
your blood and is taken to every cell in
your body

9. Majority of the cellular respiration
happens inside the mitochondria
Mitochondria

10. CELLULAR RESPIRATION
GLYCOLYSIS
Glucose Pyruvate
CYTOPLASM
PREPARATORY
REACTION
Acetyl CoA
CITRIC
ACID
CYCLE
ELECTRON
TRANSPORT
CHAIN
NADH NADH
NADH &
FADH2

12. Plants use cellular respiration to
convert the energy stored in the form
of glucose into a usable chemical
energy

13. IN RESPIRATION…
Plants uses oxygen, glucose and
produces carbon dioxide, water and
energy. During respiration, carbon is
attach to the O2 and release CO2 so it
can be used for photosynthesis.

14. IN PHOTOSYNTHESIS…
Plants take in carbon dioxide, water
and sunlight and use them to make
food. Their food is simple sugar —
glucose.

15. Plants pull the carbon off CO2 and use
the carbon in glucose, freeing the oxygen so it can be
used for respiration.
(They do not need the oxygen for this. They get that from water, H2O.)
GLUCOSE
C6H12O6

17. Is it good to sleep under a tree
at night?

18. Basic idea about the Oxygen Cycle
Man eats food, breaks it
down and releases CO2
through respiration.
Man gives off CO2,
which is taken in by the
plant.
Plant uses CO2 to make
food.
Plant gives off O2,
which is taken in by the
man

19. This happens on land and in the water.
Algae and aquatic plants produce food
underwater through photosynthesis.

20. They use CO2 dissolved in the water.
Other aquatic organisms use the
dissolved oxygen these plants release into
the water.

21. One big cycle — all living things depend on each other for it to work!

22. We keep destroying natural areas, especially forested areas with many
plants and replacing them with buildings, parking lots, lawns, etc. Fewer
plants mean less oxygen and more carbon dioxide. This disturbs the
balance of the natural cycle.