1. CHAPTER 5 PHOTOSYNTHESIS
Title
CHAPTER 5
PHOTOSYNTHESIS

2. 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

3. Photosynthesis title, definition and equation.

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

5. 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.

6. Why does a leaf look green?

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

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

9. Action spectrum of photosynthesis shows wavelengths used for light dependent reactions. Different colours are different wavlengths. The green region is not used, so green light is reflected and seen.

10. Absorption spectrum of chlorophyll a vs action spectrum of photosynthesis. Chlorophyll b is used to ‘fill the gaps’ in the action spectrum.

11. Fig. 7.2

12. Image source unknown. Question from the IBO.
Chloroplast: structure’s relationship with function
Image source unknown. Question from the IBO.

13. Chloroplasts contain several pigments
Chloroplast Pigments
Chloroplasts contain several pigments
Chlorophyll a (dark green)
Chlorophyll b (light green)
Carotene (orange)
Xanthophyll (yellow)
Lycopene (red)
Figure 7.7

15. Chl b has a carbonyl group
Chlorophyll a & b
Chl a has a methyl group
Chl b has a carbonyl group
Porphyrin ring
delocalized e-
Phytol tail

16. Absorption Spectrum for Various Plant Pigments

17. Excitation of chlorophyll in a chloroplast
the photons of light excite electrons in chlorophyll. When they lose this energy the electrons emit a longer wavelength - red. e e
Excited
state 2
Heat
Light
Light
(fluorescence)
Photon
Ground
state
Chlorophyll
molecule
(a) Absorption of a photon
(b) fluorescence of isolated chlorophyll in solution

18. There are 2 sets of reactions in Photosynthesis 1) Light dependent reactions (photo) 2) Light independent reactions (synthesis)

19. Light dependent reactions (photo) Solar energy is trapped by pigments and used to generate 2 high-energy compounds: ATP and NADPH and O2 This occurs in the thylakoids in the chloroplasts

20. Two types of photosystems cooperate in the light reactions
Photon
ATP
mill
Photon
Water-splitting
photosystem
NADPH-producing
photosystem

21. Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product
Primary electron acceptor
Electron transport chain
Electron transport
Photons
PHOTOSYSTEM I
PHOTOSYSTEM II
Energy for synthesis of
by chemiosmosis

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

23. Chemiosmosis The linking of H+ ions moving down a concentration gradient to the synthesis of ATP from ADP.
Energy from the electron transport chain between PSII and PSI is used to pump H+ ions from the stroma to the inner thylakoid space

24. Chemiosmosis The linking of H+ ions moving down a concentration gradient to the synthesis of ATP from ADP.
A concentration gradient of H+ ions is generated because the thylakoid membrane is impermeable to H+ ions.

25. Chemiosmosis The linking of H+ ions moving down a concentration gradient to the synthesis of ATP from ADP.
ATP synthase, embedded in the thykaloid membrane, is the only pathway for the H+ ions to move down their concentration gradient, so it acts like a dam.

26. Chemiosmosis The linking of H+ ions moving down a concentration gradient to the synthesis of ATP from ADP.
In a dam, water flows down and turns turbines to generate electrical energy.

27. Chemiosmosis The linking of H+ ions moving down a concentration gradient to the synthesis of ATP from ADP.
Similarly, the H+ ions flowing through ATP synthase generates the energy to add a phosphate to ADP to make the high energy ATP.

28. Chemiosmosis The linking of H+ ions moving down a concentration gradient to the synthesis of ATP from ADP.
In the stroma,the energy from the electron transport chain of PSI provides the energy to combine H+ ions with NADP+ to form NADPH

29. How the Light Reactions Generate ATP and NADPH
Primary
electron
acceptor
NADP
Energy
to make
Primary
electron
acceptor 3 2
Light
Electron transport chain
Light
Primary
electron
acceptor
Reaction-
center
chlorophyll 1
NADPH-producing
photosystem
Water-splitting
photosystem
2 H + 1/2

30. Stop here

31. In the light reactions, electron transport chains generate ATP, NADPH, & O2
Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons
The excited electrons are passed from the primary electron acceptor to electron transport chains
Their energy ends up in ATP and NADPH

32. Chemiosmosis powers ATP synthesis in the light reactions
The electron transport chains are arranged with the photosystems in the thylakoid membranes and pump H+ through that membrane
The flow of H+ back through the membrane is harnessed by ATP synthase to make ATP
In the stroma, the H+ ions combine with NADP+ to form NADPH

33. Cyclic Photophosphorylation
Process for ATP generation associated with some Photosynthetic Bacteria
Reaction Center => 700 nm

34. ELECTRON TRANSPORT CHAIN
The production of ATP by chemiosmosis in photosynthesis
Thylakoid compartment (high H+)
Light
Light
Thylakoid membrane
Antenna molecules
Stroma (low H+)
ELECTRON TRANSPORT CHAIN
PHOTOSYSTEM II
PHOTOSYSTEM I
ATP SYNTHASE

35. 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

36. 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

37. Fig. 7.4

38. Fig. 7.7

39. Fig. 7.8

40. Photosynthesis Animations

41. The Calvin-Benson Cycle (light-independent reactions)

44. Fig. 7.9

45. Calvin cycle (Light-independent reactions)
(photosynthesis game – boys vs girls!)
(Rags to Riches game – photosynthesis)

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