Photosynthesis

1. +
Photosynthesis: Converting sunlight into chemical
energy
Students who demonstrate understanding can:
HS-LS1-5: Use a model to illustrate how photosynthesis transforms light energy into stored chemical
energy.

2. +
✔ For Understanding
 To understand the process of photosynthesis we need to build
off what we already know about:
Topic Examples
Molecules Water (H2O), Oxygen (O2 ), Carbon
Dioxide (CO2)
Carbohydrates Sugar (glucose)
Trophic Levels Autotrophs, Heterotrophs, Primary
Consumers
Organelles of Plant Cells Nucleus, Cell Wall, Chloroplast,
Mitochondria
Energy Source for Cells ATP
Cellular Respiration CO2 is released into the
atmosphere

3. +
In this lesson we will learn:
 Sources of Oxygen
 Autotrophs
 Where photosynthesis happens
 Structure of chloroplasts
 Two reactions of Photosynthesis
 Steps of Photosynthesis
 Locations, Reactants and Products of the
two process of photosynthesis
 Photosynthetic Equation
Driving Question: How does
photosynthesis happen?

4. Try this: Lets all take a deep breath in and then slowly
exhale out. Ready go!
 Think-Pair-Share: Where do you
think the oxygen (O2) we breathe
comes from?
 O2 is produced by different kinds of
bacteria, algae, and plants
(including trees) during
photosynthesis.
 About 25% of O2 comes from land
plants.
So where does the other 75% come
from? Well...
 Most of Earth’s O2 comes from the
ocean.
 Released from tiny ocean plants
called, phytoplankton.

5. +
Autotrophs and Photosynthesis
 Called “self feeders” or
”producers”.
 Organisms that can produce their
own food using light, water,
carbon dioxide, or other
chemicals.
 Examples of autotrophs: green
plants, some algae, few bacteria.
 Most autotrophs use
photosynthesis to make their
food.

6. +
✔ For Understanding
 Class Discuss: Where does
most of the O2 we breathe
come from? Did the answer
surprise you? What is the
difference between
heterotrophs and autotrophs?
 Think-Pair-Share: How do you
think photosynthesis happens?
What is needed for the
process?
 Excellent! Now lets learn about
WHERE and HOW
photosynthesis happens!

7. +
Class Discuss: What organelles are unique to
plant cells? Where does photosynthesis take
place in the cell?

8. + Chloroplast Anatomy: Notice this organelle has a double membrane
(inner and outer) and has special structures inside. Inside the chloroplast
are the sites of the two processes of photosynthesis. We will talk more
about those sites in a couple slides!

9. First, lets learn more about chloroplast structure and
functions!
Structure Functions
Chlorophyll (pigment)
Allows plants to absorb energy from light
Gives leaves their green color
Membrane Envelope
Protects and keep chloroplast structures enclosed
Thylakoid membrane
Flattened sac-like membrane structures called
thylakoids
Thylakoids serve as the sites of conversion of light
energy to chemical energy.
Granum
Dense layered stacks of thylakoids
Sites of conversion of light energy to chemical
energy.
Stroma
Dense fluid within the chloroplast
Lies inside the envelope but outside the thylakoid
membrane
Site of conversion of carbon dioxide to
carbohydrates
Class Discuss: Why are plants green?

10. + Now lets look at HOW photosynthesis happens:
The processes of photosynthesis is categorized
into two different reactions. These two reactions
are called, light dependent reactions and light
independent reactions. Light independent
reactions are also referred to as Calvin Cycle.
Steps of Photosynthesis
1. The pigment, chlorophyll, in the chloroplasts
absorbs light energy provided by the sun.
2. Chloroplasts use the light energy to split
water molecules into oxygen which gets
released into the atmosphere for us to
breathe. The light energy also starts the two
reactions of photosynthesis.
3. Light Reactions: Capture light energy and
uses electrons from the splitting of water to
make ATP and NADPH
4. Light Independent Reactions: Use CO2,
ATP, and NADPH to make glucose.
https://www.youtube.com/watch?v=g78utcLQrJ4

11. Summary and Location of Reactions
Light Dependent Reactions Light Independent Reactions
Location Thylakoid Membrane
Reactants
1. Sunlight
2. Water (H2O)
End Products
1. ATP
2. NADPH
3. Oxygen (O2)
Location Stroma
Reactants
1. ATP
2. NADPH
3. Carbon Dioxide
(CO2)
End Products 1. Sugar (glucose)
Class Discuss: What are the two reactions of photosynthesis? What pigment
absorbs light energy?
Think-Pair-Share: Do you think photosynthesis happens when its dark outside?
Why or why not?

12. Summary and Photosynthetic Equation
 This entire process can be summarized into
a single chemical equation:

13. Think-Pair-Share: Why is photosynthesis essential to
life on Earth? https://www.youtube.com/watch?v=eo5XndJaz-Y
Driving Question: How does photosynthesis happen?
 Light energy gets converted into chemical
energy.
 Chemical energy is stored in the form of
glucose (sugar).
 Carbon dioxide, water, and sunlight are used
to produce carbohydrates and oxygen.
 Occurs in two stages:
 Light Dependent Reactions
 Light Independent Reactions