1. PHOTOSYNTHESIS

2. PHOTOSYNTHESIS
Photosynthesis is ability of a plant to turn sunlight, air, and water into sugar (energy).
The overall reaction is: light chlorophyll CO2 + 6H2O > C6H12O6 + 6O2

3. Photosynthesis is vital to life for two reasons
1. The oxygen in the air comes from
photosynthesis. The plants continue to
replenish the oxygen in the air.
2. All of our food comes directly or
indirectly from photosynthesis.

4. Parts of a leaf Stomata palisade layer spongy layer veins chloroplast
thylakoids
grana
stroma

7. The Reactions of Photosynthesis
Remember it all occurs in the chloroplast.
Thylakoids – sac-like photosynthetic membranes inside chloroplasts, arranged in stacks called grana
Photosystems – clusters of pigments in thylakoid
Stroma – region outside of the thylakoid membrane (Calvin Cycle takes place)

8. Light Photosynthesis uses visible light.
Only visible light with intermediate wavelengths has enough energy to cause chemical change without destroying biological molecules.
What are the colors of the visible spectrum?
Why does a leaf look green?
A wavelength is from the top of a crest to the top of another crest. The electromagnetic spectrum ranges from gamma rays to radio waves. The visible light spectrum is from about 400 to 750 manometers (1 billionth of a meter). The short high frequency waves of gamma rays have too much energy and break the hydrogen bonds. The longer waves of heat, microwaves and radio waves do not have enough and are absorbed by the water in the plant.

9. Pigments Light is captured by pigments.
The main photosynthetic pigment is chlorophyll.
There is chlorophyll a, b and c.
Chlorophyll a is the major photosynthetic pigment and is found in all photosynthetic plants, protist, and cyanobacteria.

10. Carotenoids Accessory pigments found in all green plants.
They absorb blue and green wavelengths and give a plant a yellow or orange color.
In the fall when chlorophyll breaks down, it is the accessory pigments which give colors of fall.

11. Accessory Pigments
The red color of some autumn leaves is due to the anthocyanin pigments. These are not photosynthetic.

12. Stages of Photosynthesis

13. Putting it all together
CO2
H2O
C6H12O6 O2
light
energy  +
H2O
CO2
Plants make both:
energy
ATP & NADPH
sugars
sunlight
ADP
NADP
Energy Building
Reactions
Sugar Building
Reactions
NADPH
ATP O2
sugars

14. The Energy-Capturing Reactions
Light absorption
Chlorophyll a and b are antennae pigments
Electron transport
Electrons lost by chlorophyll a end up at NADP
Produce oxygen
Chemiosmotic ATP synthesis
Powered by H ion reservoir

15. The Dark Reactions
The dark reactions take place outside the thylakoid membrane.
Carbon fixation - The carbon dioxide is incorporated into an organic molecule (1C + 5C = 6C). This 6 carbon structure is unstable and immediately splits into 2, 3 carbon molecules. These molecules go through a series of reactions known as the CALVIN CYCLE.

16. What controls photosynthesis?
Intensity of light
Scarcity of water

17. Ecological Aspects
C4 PLANTS - Use more ATP but at high temperatures they can photosynthesize faster -allowing plants to grow and reproduce faster. These include many weeds and important crops such as corn.
A special variation of C4 plants are the CAM plants. These are mostly desert plants. These plants keep the stomata closed during the day and open at night. They must conserve water!

18. Energy cycle ATP Photosynthesis Cellular Respiration sun CO2 O2 H2O
even though this equation is a bit of a lie… it makes a
better story
sun
Energy cycle
Photosynthesis
CO2
H2O
C6H12O6 O2
light
energy  +
H2O
plants
CO2
glucose O2
animals, plants
CO2
H2O
C6H12O6 O2
ATP
energy  +
Cellular Respiration
ATP
The Great Circle of Life,Mufasa!