1. REACTIONS of PHOTOSYNTHESIS
REACTIONS of PHOTOSYNTHESIS

2. Law of Thermodynamics *energy cannot be created nor destroyed BUT it can change forms.
Photosynthesis converts solar energy into
chemical energy.

3. Who and Where? Photosynthesis occurs in the chloroplast.
All organisms with chloroplasts can conduct photosynthesis.

4. Chemical Equation Raw Materials Products
CO2 – from animals C6H12O6 – glucose/food
H2O – water absorbed O2 – oxygen gas used by
Chlorophyll –plant pigment animals

5. Reactions of Photosynthesis
There are two reactions involved:
Light Reactions –
* Must have light.
* Purpose – to capture light
energy.
Dark Reactions –
* Don’t need light.
* Purpose – to make glucose.

6. Light Energy colors Visible light is made up of many different
_______________of light
Your eyes “see”
different sizes of
waves as different
___________
wavelengths
colors

7. Myth:
Many people think that plants are green because they absorb and use green light in photosynthesis,
BUT
Image from:

8. BUT… We “see” reflected light
Light wavelengths that are ___________
off of objects bounce back to our eyes .
That is the ___________ we “see”
REFLECTED
COLOR
Image modified from:

9. absorbs ALL except BLUE reflected
This book “looks BLUE” because the dye in
this cover _______________ of the
wavelengths of light _________ blue.
_______ light is
____________ to your eyes and it
looks BLUE
absorbs ALL
except
BLUE
reflected

10. except red reflected The dye in this T shirt absorbs all of the
colors __________________________
Red wavelengths are
_________________ to
your eyes and the
shirt looks RED
except red
reflected
GO CATS!

11. absorbs ALL ENERGY Objects “look BLACK” because black
dye ________________ of the
wavelengths of light.
When wavelengths are absorbed so is
the_____________ of the wave.
That is why wearing a black T-shirt in the summer feels warmer than wearing
a white t-shirt.
absorbs ALL
ENERGY

12. The dye in white objects _____________ of the wavelengths of light.
_______ energy is ABSORBED
so wearing white
clothing is “cooler”.
REFLECTS ALL
LITTLE

13. (These look yellow, orange, and red) CHLOROPHYLL
The main energy
absorbing molecule
in green plants is
___________________
_________________
are plant pigments too.
(These look yellow, orange, and red)
CHLOROPHYLL
CAROTENOIDS

14. GREEN leaves have BOTH chlorophyll AND carotenoids __________________
but the huge amount of chlorophyll ______
the other colors and
leaves usually
look green
ALL THE TIME
hides

15. In ______, chlorophyll production slows as the trees shut down and photosynthesis stops for winter.
FALL

16. carotinoid colors that are usually _______ by chlorophyll
Then we can see the
carotinoid colors that are usually _______ by chlorophyll
HIDDEN

17. There are two types of chlorophyll
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There are two types of chlorophyll
__________________ & ___________________
Chlorophyll a
Chlorophyll b
Absorption of Light by
Chlorophyll a and Chlorophyll b
Chlorophyll a
absorbs the
_____ & ________
wavelengths best.
It absorbs very
little ______ light.
violet
red
Chlorophyll b
Chlorophyll a
red
Blue

18. There are two types of chlorophyll
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There are two types of chlorophyll
__________________ & ___________________
Chlorophyll a
Chlorophyll b
Absorption of Light by
Chlorophyll a and Chlorophyll b
Chlorophyll b
absorbs some
______light and
even more
_________ light.
red
Chlorophyll b
Chlorophyll a
Blue-violet
red

19. NEITHER KIND OF CHLOROPHYLL IS VERY GOOD AT ABSORBING _________ LIGHT!
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Absorption of Light by
Chlorophyll a and Chlorophyll b
NEITHER KIND OF CHLOROPHYLL IS VERY GOOD AT ABSORBING _________ LIGHT!
Chlorophyll b
Chlorophyll a
GREEN
red

20. That’s why leaves LOOK GREEN…..
That’s why leaves LOOK GREEN…..
Chlorophyll doesn’t absorb….
it ___________ GREEN light!
REFLECTS

21. That’s why plant have other pigments (like carotenoids)
That’s why plant have other pigments (like carotenoids). They help _________ some wavelengths chlorophyll _______; so the plant can __________ of the sun’s energy.
ABSORB
DOESN’T
USE MORE

22. SO WHAT WAVELENGTHS ARE BEST FOR PHOTOSYNTHESIS?
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Absorption of Light by
Chlorophyll a and Chlorophyll b
THE ONES CHLOROPHYLL ABSORBS
THE BEST
________ and
_______________
Chlorophyll b
Chlorophyll a
red
Blue-violet

23. Pearson Education Inc, Pusblishing as Pearson Prentice Hall
Because light is a form of ___________, any molecule that absorbs light also ___________the energy from the light.
ENERGY
ABSORBS

24. ENERGY & ELECTRONS When chlorophyll absorbs light, the
When chlorophyll
absorbs light, the
energy is transferred
to electrons in the
chlorophyll molecule.
These electrons make
ATP.
HIGH ENERGY ____________
make photosynthesis work!
ELECTRONS

25. Some electrons escape and energy is lost.
Luckily, another energy molecule can be
made, NADPH, by splitting the H2O.
The plant keeps the
hydrogen and releases
the oxygen as a waste
product.
Oxygen bubbles

26. Summary, light reactions.
Used – H2O, light, chlorophyll,
Produced – Energy (ATP & NADPH), O2.
Purpose – to create usable energy to fuel
the dark reactions.