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. +
Question #1: Where does the oxygen
(O2) we breathe come from?
 O2 is produced by different
kinds of bacteria, algae, and
plants (including trees)
during photosynthesis.
 About 25% of O2 comes from
land plants.
 Most of Earth’s O2 comes
from the ocean.
 Released from tiny ocean plants
called, phytoplankton.

3. +
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.

4. +
Overview of Photosynthesis
 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
NASA: Seeing
Photosynthesis From Space

5. +
Question #2: Where Does
Photosynthesis Take Place in the Cell?

6. +
Chloroplast Anatomy:

7. +
Closer Look at Chloroplast
Structures
 Chlorophyll:
 Allows plants to absorb energy
from light
 Gives leaves their green color
 Membrane Envelope:
 Inner and outer membranes
 Protects and keep chloroplast
structures enclosed.
 Thylakoid membrane:
 Internal membrane system
 Flattened sac-like membrane
structures called thylakoids
 Serve as the sites of conversion
of light energy to chemical
energy.
 Granum
 Dense layered stacks of
thylakoid sacs
 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

8. +
Two Processes of Photosynthesis
Light Dependent Reactions Light Independent Reactions
 Location: Thylakoid Membrane
 Reactants: Sunlight and water
(H2O)
 End Products: ATP, NADPH,
and O2
 Also called “Calvin Cycle” or
Dark Reactions
 Location: Stroma
 Reactants: ATP, NADPH, and
O2
 End Products: Glucose
Remember:
 Cells use ATP for energy
 NADPH is a cofactor in reactions that acts as a reducing agent

9. +
How Does It All Work?

10. +
Photosynthetic Equation
 Photosynthesis can be represented using a balanced chemical
equation:

11. +
Question #3: Why is photosynthesis
essential to life on Earth?
Well..
 Life can be sustained in plants.
 Plants provide oxygen for
humans.
We BREATHE oxygen!
 Without oxygen we cannot
survive!