1. Interest Grabber
Section 8-2
Trapping Energy
Have you ever used a solar-powered calculator? No matter where you go, as long as you have a light source, the calculator works. You never have to put batteries in it.

2. They convert light energy into electrical energy.
Interest Grabber Answers
Section 8-2
1. A solar-powered calculator uses solar cells that are found in rows along the top of the calculator. Into what kind of energy is the light energy converted so that the calculator works?
They convert light energy into electrical energy.
Section 2 Answers

3. Plants convert light energy into chemical energy.
Interest Grabber Answers
Section 8-2
2. Recall that plants use light energy from the sun to make food. Into what kind of energy is the light energy converted by plants?
Plants convert light energy into chemical energy.
Section 2 Answers

4. Leaves are green, as are some stems.
Interest Grabber Answers
Section 8-2
3. Most plants, no matter what size or shape they are, have some parts that are green. Which parts of a plant are usually green?
Leaves are green, as are some stems.
Section 2 Answers

5. Interest Grabber Answers
Section 8-2
4. What does the green color have to do with the plant’s ability to convert light energy into the energy found in the food it makes?
The green color is the pigment chlorophyll, which absorbs light energy from the sun and converts it to chemical energy in the process of photosynthesis.
Section 2 Answers

6. Research into PHOTOSYNTHESIS began centuries ago with this
simple question:
When a tiny seed grows into a
huge plant, where does all the
“new plant” come from?

7. PHOTO
SYNTHESIS
Light
To put together

8. What causes plants to grow?
History
What causes plants to grow?
Jan van Helmont
1600's
says
"soil"

9. Found mass of small tree & mass of soil. Planted tree.+

10. 5 years later... CONCLUSION: Plants need water to grow.
Tree gained 75 kg, soil lost no mass.
CONCLUSION: Plants need water to grow.

11. Joseph Priestley
1700's
CONCLUSION: “Something” in air is needed for candle to burn.

12. After additional experimenting, Priestley found that if he placed a mint plant in the jar for a few days, the candle could be re-lighted and would remain lit for a while!
CONCLUSION: The plant produces the “something” that the candle needs. (We now call it “oxygen.”)

13. Jan Ingenhousz
Later 1700's
CONCLUSION: Plants need light to produce oxygen.

14. Now we know... Importance? 6 CO2 + 12 H2O C6H12O6 + 6 O2 + 6 H2O
light
6 CO H2O C6H12O O H2O
pigments
“Pigments trap light energy and use that energy to covert carbon dioxide and water into carbohydrates (glucose), oxygen, and water.” PHOTOSYNTHESIS
Importance?
Produces food for all living organisms
Produces the oxygen required to break down food during cellular respiration

15. PHOTOSYNTHESIS: Reactants & Products
LIGHT ENERGY
6CO2 + 12H2O
SUGAR + 6O2 + 6 H2O

16. The Nature of Light Light travels in waves
Wavelength determines energy
Short wavelength =
high energy
Long wavelength =
low energy

17. different wavelengths as different ___________ wavelengths
Sunlight is made up
of many different
_______________
of light
Your eyes “see”
different wavelengths as
different ___________
wavelengths
colors

18. Sizes of Wavelengths

19. The Nature of Light ROY G BIV
Most of the solar radiation hitting the earth’s surface is within the visible spectrum:
ROY G BIV
Red, orange, yellow, green, blue, indigo, violet
Pigments absorb different portions of the spectrum (meaning different wavelengths or colors)
PREDICT: Which wavelengths of light will plants absorb best?

20. REACTIONS of PHOTOSYNTHESIS 8-2
REACTIONS of PHOTOSYNTHESIS 8-2

21. Plants gather the sun’s energy with light absorbing molecules called ___________.
pigments
By: VanderWal

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

23. Carotenoids are usually _______ by the presence of _______________
HIDDEN
Carotenoids are usually _______
by the presence of _______________
chlorophyll

24. ____________ in the _______,
When chlorophyll
____________ in the _______,
we can see the carotenoid colors that are there ____________, but are no longer hidden.
FALL
DISAPPEARS
ALL THE TIME

25. There are two types of chlorophyll
© Pearson Education, Inc. Publishing asPearson Prentice-Hall. All rights reserved.
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

26. There are two types of chlorophyll
© Pearson Education, Inc. Publishing asPearson Prentice-Hall. All rights reserved.
There are two types of chlorophyll
__________________ & ___________________
Chlorophyll a
Chlorophyll b
Absorption of Light by
Chlorophyll a and Chlorophyll b
Chlorophyll b
absorbs
______light and
even more
_________ light.
red
Chlorophyll b
Chlorophyll a
Blue-violet
red

27. NEITHER KIND OF CHLOROPHYLL IS VERY GOOD AT ABSORBING _________ LIGHT!
© Pearson Education, Inc. Publishing asPearson Prentice-Hall. All rights reserved.
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

28. 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

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

30. REMEMBER: Chlorophyll a & b ______________ absorb do NOT
Absorption of Light by
Chlorophyll a and Chlorophyll b
© Pearson Education, Inc. Publishing as
Pearson Prentice-Hall. All rights reserved.
REMEMBER:
Chlorophyll a & b
______________
absorb
_______________
wavelengths of
light
Chlorophyll b
do NOT
Chlorophyll a
green

31. Why are plants green? BECAUSE… Chlorophyll _____________
light very well in the
__________________
regions and
_________ light
in the green
regions of spectrum.
absorbs
blue-violet and red
reflects

32. We “see” reflected light
___________________________________
REFLECTED
Light wavelengths that are ___________
bounce back to your eyes . . .
so leaves “LOOK” green.
Image modified from:

33. When you see a plant with yellow flowers and green leaves, the plant
is ____________________________
wavelengths of light
reflecting yellow and green
By: VanderWal

34. When you see a plant with __________ and __________ flowers,
the plant is reflecting yellow and purple wavelengths of light.
yellow
purple
By: VanderWal

35. Plants ________________ mainly ___________________________
wavelengths of light for photosynthesis.
absorb and use
red and blue-violet
By: VanderWal

36. 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

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

38. See a video clip about
PHOTOSYNTHESIS(8B)

39. PHOTOSYNTHESIS Light-Dependent Reaction oxygen Light & Water
ATP
NADPH
(CH2O)n
Carbon Dioxide
Light-Independent Reactions
Calvin Cycle