1. Photosynthesis is the process a plant uses to make food and grow.
A definition:
Photosynthesis is the process a plant uses to make food and grow.

2. Four things are needed for photosynthesis:
SUNLIGHT
Gives the plant energy
CHLOROPHYLL
The green stuff where the chemical reactions happen
WATER
Travels up from the roots
CARBON DIOXIDE
Enters the leaf through small holes on the underneath

3. The word and chemical equations for photosynthesis:
Sunlight
Carbon dioxide + water glucose + oxygen
6CO H20 C6H12O O2
Chlorophyll
Sunlight
Chlorophyll

4. THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON EARTH

5. THE BASICS OF PHOTOSYNTHESIS
Almost all plants are photosynthetic autotrophs, as are some bacteria and protists
Autotrophs generate their own organic matter through photosynthesis
Sunlight energy is transformed to energy stored in the form of chemical bonds
(c) Euglena
(d) Cyanobacteria
(b) Kelp
(a) Mosses, ferns, and
flowering plants

6. AN OVERVIEW OF PHOTOSYNTHESIS
Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water
Carbon dioxide
Water
Glucose
Oxygen gas
PHOTOSYNTHESIS

7. AN OVERVIEW OF PHOTOSYNTHESIS
The light reactions convert solar energy to chemical energy
Produce ATP & NADPH
Light
Chloroplast
NADP
ADP
+ P
The Calvin cycle makes sugar from carbon dioxide
ATP generated by the light reactions provides the energy for sugar synthesis
The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose
Calvin
cycle
Light
reactions

8. Light Energy Harvested by Plants & Other Photosynthetic Autotrophs
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

9. WHY ARE PLANTS GREEN? It has to do with sunlight!
Sunlight is a form of electromagnetic energy, which travels in waves.

10. Electromagnetic Spectrum and Visible Light
Gamma rays
Infrared & Microwaves
X-rays UV
Radio waves
Visible light
Wavelength (nm):
Distance between two waves

11. WHY ARE PLANTS GREEN?
Different wavelengths of visible light are seen by the human eye as different colors.
Gamma rays
Micro- waves
Radio
waves
X-rays UV
Infrared
Visible light
Wavelength (nm)

12. The feathers of male cardinals are loaded with carotenoid pigments
The feathers of male cardinals are loaded with carotenoid pigments. These pigments absorb some wavelengths of light and reflect others.
Reflected light
Sunlight minus absorbed wavelengths or colors equals the apparent color of an object.

13. THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED
Chloroplasts absorb light energy and convert it to chemical energy
Reflected
light
Light
Absorbed
light
Transmitted
light
Chloroplast

14. Photosynthesis occurs in chloroplasts
In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts
A chloroplast contains:
stroma, a fluid (site of Calvin Cycle)
grana, stacks of thylakoids (site of Light reactions)
The thylakoids contain chlorophyll
Chlorophyll is the green pigment that captures light for photosynthesis

15. The location and structure of chloroplasts
LEAF CROSS SECTION
MESOPHYLL CELL
LEAF
Mesophyll
CHLOROPLAST
Intermembrane space
Outer
membrane
Granum
Inner membrane
Grana
Stroma
Thylakoid compartment
Stroma
Thylakoid

16. Chloroplast Pigments Chloroplasts contain several pigments
Chlorophyll a: absorbs mainly violet and red light the best
Chlorophyll b: absorbs blue and orange light the best
Carotenoids: absorbs blue and green best
Figure 7.7

17. Different pigments absorb light differently

18. Paper Chromatography
A laboratory test used to separate and analyze different pigments in a leaf.
Example:

19. Photosystems: Clusters of pigments in thylakoid membrane
Photosystem I
Traps light energy and transfers the light-excited electrons to an electron transport chain.
Those excited electrons are replaced by splitting a molecule of water, which releases oxygen.
The electron transport chain releases energy, which is used to make ATP
Photosystem II
Produces NADPH by transferring excited electrons and hydrogen ions to NADP+.

20. Light Reactions Photosystem I and Photosystem II
SUMMARY: In the light reactions, electron transport chains generate ATP, NADPH, & O2
Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons
The excited electrons are passed from the primary electron acceptor to electron transport chains
The light reactions convert light energy to the chemical energy of ATP and NADPH
Watch the following animation:

21. Two types of photosystems cooperate in the light reactions
Inputs:
Water
Sunlight energy
Outputs:
Oxygen
ATP
NADPH
Photon
ATP
mill
Photon
Water-splitting
photosystem
NADPH-producing
photosystem

22. Plants produce O2 gas by splitting H2O
The O2 liberated by photosynthesis is made from the oxygen in water (H+ and e-)

23. How the Light Reactions Generate ATP and NADPH
Primary
electron
acceptor
NADP
Energy
to make
Primary
electron
acceptor 3 2
Light
Electron transport chain
Light
Primary
electron
acceptor
Reaction-
center
chlorophyll 1
NADPH-producing
photosystem
Water-splitting
photosystem
2 H + 1/2

24. ELECTRON TRANSPORT CHAIN
The production of ATP in photosynthesis
Thylakoid compartment (high H+)
Light
Light
Thylakoid membrane
Antenna molecules
Stroma (low H+)
ELECTRON TRANSPORT CHAIN
PHOTOSYSTEM II
PHOTOSYSTEM I
ATP SYNTHASE

25. A Photosynthesis Road Map
Chloroplast
Light
Stroma
NADP
Stack of
thylakoids
ADP
+ P
Light
reactions
Calvin
cycle
Sugar used for
 Cellular respiration
 Cellulose
 Starch
 Other organic compounds

26. Calvin Cycle
Called a cycle because the starting material, RuBP, is regenerated.
Uses carbon from carbon dioxide, the energy from ATP, and high energy electrons and hydrogen ions from NADPH to make a small sugar named G3P.
The plant uses G3P to make glucose and other organic molecules.
Overall input:
CO2, ATP, NADPH
Overall output:
Glucose

28. Calvin Cycle Watch the following animation:

29. Review: Photosynthesis uses light energy to make food molecules
Light reactions use water and produce oxygen.
The Calvin Cycle uses ATP and NADPH created in the the light reactions to convert carbon dioxide to glucose.
Chloroplast
Light
Photosystem II Electron transport chains Photosystem I
CALVIN CYCLE
Stroma
Electrons
Cellular respiration
Cellulose
Starch
Other organic compounds
LIGHT REACTIONS
CALVIN CYCLE

31. Animation is of the Calvin Cycle Note what happens to the carbon dioxide and what the end product is.
Second animation of the Calvin Cycle is very clear and even does the molecular bookkeeping for you.