1. Photosynthesis Life Is Solar Powered!

2. What Would Plants Look Like On Alien Planets?

3. Why Would They Look Different?
Different Stars Give off Different types of light or Electromagnetic Waves
The color of plants depends on the spectrum of the star’s light, which astronomers can easily observe. (Our Sun is a type “G” star.)

4. Anatomy of a Wave Wavelength
Is the distance between the crests of waves
Determines the type of electromagnetic energy

5. Electromagnetic Spectrum
Is the entire range of electromagnetic energy, or radiation
The longer the wavelength the lower the energy associated with the wave.

6. Visible Light
Light is a form of electromagnetic energy, which travels in waves
When white light passes through a prism the individual wavelengths are separated out.

7. Visible Light Spectrum
Light travels in waves
Light is a form of radiant energy
Radiant energy is made of tiny packets of energy called photons
The red end of the spectrum has the lowest energy (longer wavelength) while the blue end is the highest energy (shorter wavelength).
The order of visible light is ROY-G-BIV
This is the same order you will see in a rainbow b/c water droplets in the air act as tiny prisms

8. Light Options When It Strikes A Leaf
Reflected
Chloroplast
Absorbed
light
Granum
Transmitted
Figure 10.7
Reflect – a small amount of light is reflected off of the leaf. Most leaves reflect the color green, which means that it absorbs all of the other colors or wavelengths.
Absorbed – most of the light is absorbed by plants providing the energy needed for the production of Glucose (photosynthesis)
Transmitted – some light passes through the leaf

10. Photosynthesis Overview
Concept Map
Photosynthesis
includes
Light
dependent
reactions
Light
independent
reactions
occurs in
uses
uses
occur in
Light
Energy
Thylakoid
membranes
Stroma
ATP
NADPH
to produce of
to produce
ATP
NADPH O2
Chloroplasts
Glucose

11. Anatomy of a Leaf Figure 10.3 Leaf cross section Vein Mesophyll CO2 O2
Stomata

13. Chloroplast

14. Chloroplast Are located within the palisade layer of the leaf
Stacks of membrane sacs called Thylakoids
Contain pigments on the surface
Pigments absorb certain wavelenghts of light
A Stack of Thylakoids is called a Granum
Chloroplast
Mesophyll
5 µm
Outer
membrane
Intermembrane
space
Inner
Thylakoid
Granum
Stroma
1 µm

15. Pigments Are molecules that absorb light
Chlorophyll, a green pigment, is the primary absorber for photosynthesis
There are two types of cholorophyll
Chlorophyll a
Chlorophyll b
Carotenoids, yellow & orange pigments, are those that produce fall colors. Lots of Vitamin A for your eyes!
Chlorophyll is so abundant that the other pigments are not visible so the plant is green…Then why do leaves change color in the fall?

16. Color Change
In the fall when the temperature drops plants stop making Chrlorophyll and the Carotenoids and other pigments are left over (that’s why leaves change color in the fall).

17. Wavelength of light (nm)
The absorption spectra of three types of pigments in chloroplasts
Three different experiments helped reveal which wavelengths of light are photosynthetically important. The results are shown below.
EXPERIMENT
RESULTS
Absorption of light by
chloroplast pigments
Chlorophyll a
(a) Absorption spectra. The three curves show the wavelengths of light best absorbed by three types of chloroplast pigments.
Wavelength of light (nm)
Chlorophyll b
Carotenoids
Figure 10.9

18. The action spectrum of a pigment
Profiles the relative effectiveness of different wavelengths of radiation in driving photosynthesis
(measured by O2 release)
Rate of photosynthesis
Action spectrum. This graph plots the rate of photosynthesis versus wavelength. The resulting action spectrum resembles the absorption spectrum for chlorophyll a but does not match exactly (see part a). This is partly due to the absorption of light by accessory pigments such as chlorophyll b and carotenoids.
(b)

19. The action spectrum for photosynthesis
Was first demonstrated by Theodor W. Engelmann
400
500
600
700
Aerobic bacteria
Filament
of alga
Engelmann‘s experiment. In 1883, Theodor W. Engelmann illuminated a filamentous alga with light that had been passed through a prism, exposing different segments of the alga to different wavelengths. He used aerobic bacteria, which concentrate near an oxygen source, to determine which segments of the alga were releasing the most O2 and thus photosynthesizing most.
Bacteria congregated in greatest numbers around the parts of the alga illuminated with violet-blue or red light. Notice the close match of the bacterial distribution to the action spectrum in part b.
(c)
Light in the violet-blue and red portions of the spectrum are most effective in driving photosynthesis.
CONCLUSION

20. Absorption of chlorophylls a and b at various wavelengths in the visible light spectrum

21. 1. Based on the data and your graphs, what can you conclude about the two chlorophylls and their absorption spectra? (2)(In what ways are they similar? (2) Different?
Similar- both have two peaks. For both graphs the peak is the higher in the blue end. Both have a valley in the green part of the spectrum.
Different- Chlorophyll B peaks more in blue, whereas chlorophyll a has its peak to the left in violet. (they are at different wavelengths of light)

22. 2. Chlorophylls are the predominant pigments in leaves
2. Chlorophylls are the predominant pigments in leaves. Based on the data and your graph. Give a possible explanation for why plants are green.
(2) Any reasonable explanation accepted that connects to the data…Chlorophyll absorbs light in the red and blue ends of the light spectrum but not green. So green is reflected back to our eyes and that is what we see.

23. (2) reasonable explanation…Reflected and/or transmitted (goes through)
3. If some wavelengths (colors) of light are absorbed by chlorophylls, what happens to the other wavelengths of light that are not absorbed? Give any possibilities that you can think of.
(2) reasonable explanation…Reflected and/or transmitted (goes through)

24. Follow Up Questions
1. Explain why leaves are green. Begin your explanation with white light coming from the sun and ending in your eye. (4)
White Light from the sun  hits leaf  all wavelengths (colors) absorbed but green  green reflected to our eyes

25. Graph X-axis: Wavelength (2) units: nanometers (1)
Y -axis: % absorption (2)
Line graph for carotenoids (2)
Appropriate title- Absorption of carotenoids at various wavelengths in the visible light spectrum (2)

26. Pigment Molecules that absorb specific wavelengths of light
Chlorophyll absorbs reds & blues and reflects green
Xanthophyll absorbs red, blues, greens & reflects yellow
Carotenoids reflect orange

27. Chlorophyll Green pigment in plants Traps sun’s energy
Sunlight energizes electron in chlorophyll

28. What is beta carotene. Where is it found. What does it do for plants
What is beta carotene? Where is it found? What does it do for plants? Why is it beneficial in a human diet? (4 extra credit)
Beta-carotene is one of a group of natural chemicals known as carotenes or carotenoids. Carotenes are responsible for the orange color of many fruits and vegetables such as carrots, pumpkins, and sweet potatoes.
Beta carotene is converted in the body to vitamin A. It is an antioxidant, like vitamins E and C.

29. Chlorophyll Chlorophyll a Chlorophyll b
Is the main photosynthetic pigment
Chlorophyll b
Is an accessory pigment C CH
CH2 N
H3C Mg H
CH3 O
CHO
in chlorophyll a
in chlorophyll b
Porphyrin ring:
Light-absorbing
“head” of molecule
note magnesium
atom at center
Hydrocarbon tail:
interacts with hydrophobic
regions of proteins inside
thylakoid membranes of
chloroplasts: H atoms not
shown
Figure 10.10

30. PHOTOSYNTHESIS
Comes from Greek Word “photo” meaning “Light” and “syntithenai” meaning “to put together”
Photosynthesis puts together sugar molecules using water, carbon dioxide, & energy from light.

31. Happens in two phases Light-Dependent Reaction
Converts light energy into chemical energy
Light-Independent Reaction
Produces simple sugars (glucose)
General Equation
6 CO2 + 6 H2O  C6H12O6 + 6 O2

32. First Phase Requires Light = Light Dependent Reaction
Sun’s energy energizes an electron in chlorophyll molecule
Electron is passed to nearby protein molecules in the thylakoid membrane of the chloroplast

33. Excitation of Chlorophyll by Light
When a pigment absorbs light
It goes from a ground state to an excited state, which is unstable
Excited
state
Energy of election
Heat
Photon
(fluorescence)
Chlorophyll
molecule
Ground e–
Figure A

34. If an isolated solution of chlorophyll is illuminated
It will fluoresce, giving off light and heat
Figure B

35. ETC
Electron from Chlorophyll is passed from protein to protein along an electron transport chain
Electrons lose energy (energy changes form)
Finally bonded with electron carrier called NADP+ to form NADPH or ATP
Energy is stored for later use

36. Two Photosystems
Photosystem II: Clusters of pigments boost e- by absorbing light w/ wavelength of ~680 nm
Photosystem I: Clusters boost e- by absorbing light w/ wavelength of ~760 nm.
Reaction Center: Both PS have it. Energy is passed to a special Chlorophyll a molecule which boosts an e-

38. A mechanical analogy for the light reactions
Mill
makes
ATP e–
Photon
Photosystem II
Photosystem I
NADPH
Figure 10.14 

39. (INTERIOR OF THYLAKOID)
Photosystem
A photosystem
Is composed of a reaction center surrounded by a number of light-harvesting complexes
Primary election
acceptor
Photon
Thylakoid
Light-harvesting
complexes
Reaction
center
Photosystem
STROMA
Thylakoid membrane
Transfer
of energy
Special
chlorophyll a
molecules
Pigment
THYLAKOID SPACE
(INTERIOR OF THYLAKOID)
Figure 10.12 e–

40. Where those electrons come from
Water
Electrons from the splitting of water (photolysis) supply the chlorophyll molecules with the electrons they need
The left over oxygen is given off as gas

41. The Splitting of Water Chloroplasts split water into
Hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules
6 CO2
12 H2O
Reactants:
Products:
C6H12O6
6 H2O
6 O2
Figure 10.4

42. High Quality H2O Photolysis – Splitting of water with light energy
Hydrogen ions (H+) from water are used to power ATP formation with the electrons
Hydrogen ions (charged particle) actually move from one side of the thylakoid membrane to the other
Chemiosmosis – Coupling the movement of Hydrogen Ions to ATP production

43. Animation – takes a min. to load…be patient
Animation II – Does not take as long to load but it is not as good

44. The light reactions and chemiosmosis: the organization of the thylakoid membrane
REACTOR
NADP+
ADP
ATP
NADPH
CALVIN
CYCLE
[CH2O] (sugar)
STROMA
(Low H+ concentration)
Photosystem II
H2O
CO2
Cytochrome
complex O2 1
1⁄2 2
Photosystem I
Light
THYLAKOID SPACE
(High H+ concentration)
Thylakoid
membrane
synthase Pq Pc Fd
reductase
+ H+
NADP+ + 2H+ To
Calvin
cycle P 3 H+
2 H+
+2 H+
Figure 10.17

45. Vocabulary Review Light-Dependent Pigment Chlorophyll
Electron Transport Chain
ATP
NADPH
Photolysis
Chemiosmosis

46. Light-Dependent
Converts light into chemical energy (ATP & NADPH are the chemical products). Oxygen is a by-product
Mill
makes
ATP e–
Photon
Photosystem II
Photosystem I
NADPH
Figure 10.14 

47. Electron Transport Chain
Series of Proteins embedded in a membrane that transports electrons to an electron carrier

48. ATP Adenosine Triphosphate
Stores energy in high energy bonds between phosphates

49. NADPH Made from NADP+; electrons and hydrogen ions
Made during light reaction
Stores high energy electrons for use during light-Independent reaction (Calvin Cycle)

50. Chemiosmosis
The combination of moving hydrogen ions across a membrane to make ATP

51. Figure 10.5 H2O CO2 [CH2O] O2 (sugar) Light LIGHT REACTIONS CALVIN
CYCLE
Chloroplast
[CH2O]
(sugar)
NADPH
NADP 
ADP
+ P O2
Figure 10.5
ATP

52. PART II LIGHT INDEPENDENT REACTION Also called the Calvin Cycle
No Light Required
Takes place in the stroma of the chloroplast
Takes carbon dioxide & converts into sugar
It is a cycle because it ends with a chemical used in the first step

53. Begins & Ends The Calvin Cycle begins and ends with RuBP
CO2 is added to RuBP; “fixing” the CO2 in a compound
One compound made along the way is PGAL
PGAL can be made into sugars or RuBP
Calvin Cycle uses ATP & NADPH

54. The Calvin cycle Figure 10.18 Input Light 3 CO2 CALVIN CYCLE
(G3P)
Input
(Entering one
at a time)
CO2 3
Rubisco
Short-lived intermediate
3 P P
Ribulose bisphosphate (RuBP)
3-Phosphoglycerate
6 P 6
1,3-Bisphoglycerate
6 NADPH
6 NADPH+
Glyceraldehyde-3-phosphate
6 ATP
ATP
3 ADP
CALVIN
CYCLE 5 1
G3P (a sugar) Output
Light
H2O
LIGHT REACTION
ATP
NADPH
NADP+
ADP
[CH2O] (sugar)
CALVIN CYCLE
Figure 10.18 O2
6 ADP
Glucose and other organic compounds
Phase 1: Carbon fixation
Phase 3: Regeneration of the CO2 acceptor (RuBP)
Phase 2: Reduction

55. Chloroplast – Where the Magic Happens!+
H2O
CO2
Energy
ATP and
NADPH2
Which splits
water
Light is Adsorbed By
Chlorophyll
Calvin Cycle
ADP
NADP
Chloroplast
Used Energy and is recycled. O2 +
C6H12O6
Light Reaction
Dark Reaction
6 CO H2O + Light energy  C6H12O6 + 6 O2 + 6 H2 O