1. Photosynthesis

2. Objectives Explain the importance of photosynthesis.
Write and interpret the chemical equation for photosynthesis.
Check Your Understanding
How are plant cells different from animal cells?
In what organelle does photosynthesis take place?

3. All Energy on Earth comes from the Sun!!

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

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. Food Chain

7. Overview Carbon dioxide and water are taken in by plants
Plants absorb light energy and convert it to a usable form.
ATP
Energy is used to “fix” carbon dioxide into sugar molecules
Chemical energy
Sugar is converted to starch and stored for use by the plant, and by animals when they eat plants.

8. 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

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

10. 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)

11. 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.

12. Why are plants green?
Reflected light
Transmitted light

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

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

15. Chloroplasts Have TWO membranes
A “bi-bilayer!”
The inner membrane is called the thylakoid.
The thylakoid is folded and looks like stacks of coins called granum (grana singular).
The stroma is the space surrounding the granum
Image source:

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

21. 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

22. 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

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