Photosynthesis and respiration are related as they are opposite but complementary chemical reactions. Photosynthesis uses carbon dioxide, water and sunlight to produce oxygen and glucose in plants. Respiration in organisms uses glucose and oxygen to produce carbon dioxide and water. Together they form a cycle providing energy and essential molecules for living things.

1. Photosynthesis
and
Respiration
How are they related?

2. Photosynthesis
The process of photosynthesis is a
chemical reaction.
It is the most important chemical
reaction on our planet.

3. What is the Process?
 The process of changing light energy (from the sun or other light
source) to chemical energy
 This energy is stored as sugar (a carbohydrate)
 Occurs in plants and some algae
 Plants need light energy,
CO 2 , and H 2 O
 Photosynthesis takes place
in the chloroplasts, using
chlorophyll, the green
pigment in plants

4. What Happens in this
Chemical Reaction?

5. How Do Scientists Write
this Chemical Reaction?
What does this mean?
 Six molecules of carbon dioxide react with six
molecules of water to form 1 molecule of glucose
and six molecules of oxygen.

6. HUH?
 Plants capture light energy and use that
energy to make sugar (which can be
changed to starch, a carbohydrate, also)
 Sunlight provides the energy needed by
chlorophyll to change molecules of carbon
dioxide and water into glucose
 Oxygen is also released in this reaction

7. Why Is This So Important?
 We cannot make our own food (glucose,
energy), we must get our food from plants.
 Plants are the first step in the food chain.
 The oxygen released during photosynthesis
is necessary for all living things.

8. Respiration
 There are two types:

9. What is Cellular
Respiration?
 The process of cellular respiration
is a chemical reaction.
It is the most important chemical
reaction in our bodies

10. What is the Process?
 Cellular respiration is a
process, like
photosynthesis.
 Cellular respiration takes
place in the mitochondria.
 The mitochondria take in
nutrients (glucose and
oxygen), break them down,
and create energy for the
cell.
 This process of creating
cell energy is known as
cellular respiration.
 Takes place in all living
things

11. Let’s Write the Chemical
Equation
Glucose + Oxygen ----  Carbon Dioxide +
Water
Or another way of writing the equation is:
C 6 H 12 O 6 + 6O 2 ---- 6CO 2 + 6H 2 O

12. Notice Any Similarities?

13. Notice any now?

14. Any Similarities with
These?

15. Photosynthesis and
Respiration are Related
 It is the basic cycle on Earth.