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

2. Energy can be transformed from one form to another
FREE ENERGY
(available for work)
vs.
HEAT
(not available for work)

3. THE BASICS OF PHOTOSYNTHESIS
Almost all plants are photosynthetic autotrophs, as are some bacteria and protists
Phototrophs are autotrophs that 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

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

5. Food Chain

6. THE FOOD WEB
Photosynthesis provides a vital connection between the Sun and the energy needs of living organisms.

7. WHY ARE PLANTS GREEN?
It's not that easy bein' green Having to spend each day the color of the leaves When I think it could be nicer being red or yellow or gold Or something much more colorful like that…
Kermit the Frog

8. Electromagnetic Spectrum and Visible Light
Gamma rays
Infrared & Microwaves
X-rays UV
Radio waves
Visible light
Wavelength (nm)

9. WHY ARE PLANTS GREEN?
Different wavelengths of visible light are seen by the human eye as different colors. Pigments are substances that absorb light of a certain wavelength
Gamma rays
Micro- waves
Radio
waves
X-rays UV
Infrared
Visible light
Wavelength (nm)
Visible light has wavelengths from 3600 ◦A (violet) to 7600 ◦A (red).Light energy (photons) give energy to the electrons of the absorbing pigment

10. 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
RED appears RED because the red wavelength is NOT being absorbed by the red pigment but is reflected into our eyes.

11. Why are plants green?
Reflected light

12. WHY ARE PLANTS GREEN? Plant Cells have Green Chloroplasts
The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).

13. THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED
Chloroplasts absorb light energy and convert it to chemical energy
Chlorophylls- green-yellow is not absorbed, all other colors are. Chlorophylls receive energy from violet, blue, orange and red.
Xanthophylls- yellow pigment
Carotenes- orange pigments.
Reflected
light
Light
Absorbed
light
Transmitted
light
Chloroplast

14. 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

15. 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

16. Chloroplasts: Sites of Photosynthesis
Occurs in chloroplasts, organelles in certain plants
All green plant parts have chloroplasts and carry out photosynthesis
The leaves have the most chloroplasts
The green color comes from chlorophyll in the chloroplasts
The pigments absorb light energy

17. Photosynthesis occurs in chloroplasts
In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts
A chloroplast contains:
stroma, a fluid
grana, stacks of thylakoids
The thylakoids contain chlorophyll
Chlorophyll is the green pigment that captures light for photosynthesis

18. 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

19. Chloroplast Pigments Chloroplasts contain several pigments
Chlorophyll a
Chlorophyll b
Carotenoids
Figure 7.7

20. Chlorophyll a & b Chl a has a methyl group Chl b has a carbonyl group
Porphyrin ring
delocalized e-
Phytol tail

21. Different pigments absorb light differently

22. In the light reactions, ATP, NADPH, & O2 are Produced
Light comes in, water is split- oxygen is given off to the atmosphere. Energy is given to electrons in chlorophyll and their energy ends up in ATP and NADPH. Hydrogen in water ends up in NADPH.
Happens in the grana!
Energy captured in the
light reaction is used to
power the Dark reaction

23. Plants produce O2 gas by splitting H2O

24. 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

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

26. 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

27. The Calvin Cycle- Dark Reaction
Occurs in the Stroma
NADPH and ATP from the light reaction provide the hydrogen and the energy to power the dark reaction.
Carbon Fixation- The Calvin
Cycle “fixes” carbon dioxide
from the atmosphere into
an organic molecule-
GLUCOSE

28. Review: Photosynthesis uses light energy to make food molecules
A summary of the chemical processes of photosynthesis
Photosynthesis happens only during the day when there is light.
Chloroplast
Light
Photosystem II Electron transport chains Photosystem I
CALVIN CYCLE
Stroma
Electrons
Cellular respiration
Cellulose
Starch
Other organic compounds
LIGHT REACTIONS
CALVIN CYCLE

29. Factors that Effect Photosynthesis
Temperature- photosynthesis
occurs best at 35◦ C
Light intensity- photosynthesis
occurs best at 1/3rd summer
sunlight. Some leaves
are shaded so photosynthesis
works best for the whole plant
at higher than 1/3rd summer sunlight.

30. Factors that Effect Photosynthesis
Minerals- nitrogen, copper, magnesium, zinc iron, are necessary to make enzymes and pigments.
Water- a certain level is necessary
CO2 Level-
X10 normal CO2 concentration in air

31. It's not that easy bein' green… but it is essential for life on earth!