1. Photosynthesis

3. Properties of Light
White light from the sun is composed of a range of wavelengths.
All colors

6. Chlorophyll Chlorophyll is the main pigment that absorbs sunlight.
Chlorophyll absorbs blue light and to a lesser extent, red light.
It reflects green light

7. What do chlorophyll and fireworks have in common?

8. Introduction
Autotrophs:
Photoautotrophs :
Chemoautotrophs

9. thylakoid compartment
Chloroplast
two outer membranes
thylakoid membrane system
Organelle of photosynthesis in plants and algae
stroma
thylakoid compartment

10. Important structures
Chloroplast
Thylakoids:
Grana:
Stroma:

11. a A look inside the leaf
b One of the photosynthetic cells inside leaf
leaf’s upper epidermis
photosynthetic cell in leaf
leaf vein
Leaf Structure
leaf’s lower epidermis

12. Photosynthesis: Light-Dependent
Photosystems - chlorophyll a molecule....

13. What does Chlorophyll absorb?

14. Figure 4-15 (part 1) Capturing light energy with excited electrons.
Chlorophyll electrons are excited to a higher energy state by light energy. 14

15. Photosynthesis: Light-Dependent
pigment absorbs light energy

16. Two Potential Fates of Excited Electrons
Electron returns to resting, unexcited state.
Excited electrons are passed to other atoms.
An electron in a photosynthetic pigment that is excited to a higher energy state generally has one of two fates (refer to the next two slides also): (1) The electron returns to its resting, unexcited state. In the process, energy is released, some of which may be transferred to a nearby molecule, bumping electrons on that molecule to a higher energy state (and the rest of the energy is dissipated as heat) or (2) The excited electron itself is passed to another molecule. 16

17. Figure 4-15 (part 2) Capturing light energy with excited electrons.
Chlorophyll electrons are excited to a higher energy state by light energy. 17

18. Photosynthesis: Light-Dependent
electrons in the pigments become excited
energy (but not the electrons) is transferred
excites the electrons in a chlorophyll a molecule at the center of the photosystem.

19. Photosynthesis: Light-Dependent

20. The Passing of Electrons in Their Excited State
Molecules that gain electrons always carry greater energy than before receiving them
The passing of electrons from molecule to molecule is one of the chief ways that energy moves through cells. Many molecules carry or accept electrons during cellular activities. All that is required is that the acceptor have a greater attraction for electrons than the molecule from which it accepts them. 20

21. Photosynthesis: Light-Dependent
chlorophyll that is the reaction center
Splits water

22. Photosynthesis: Light-Dependent

23. Photosynthesis: Light-Dependent
chlorophyll a continually loses its excited electrons to a nearby molecule,
replacement electrons come from water.

24. ATP
Adenine
Ribose
3 Phosphate groups

25. ATP ATP Adenosine diphosphate (ADP) + Phosphate
Energy
Adenosine diphosphate (ADP) + Phosphate
Adenosine triphosphate (ATP)
Partially
charged
battery
Fully

26. Photosynthesis: Light-Dependent

27. Photosynthesis: Light-Dependent
Protons rush out of the thylakoid sacs with great force—to build energy-storing ATP molecules

28. Light-Dependent

29. Photosynthesis: Light-Dependent
Product #1 of the “Photo” Portion of Photosynthesis: ATP
Product #2: NADPH
Product #3 (waste): O2

30. Photosynthesis Equation
LIGHT ENERGY
6H2O + 6CO2
6O2 + C6H12O6
6 water +
6 carbon dioxide
6 oxygen
+ glucose

31. Suppose a large meteor hit the earth
Suppose a large meteor hit the earth. How could smoke and soot in the atmosphere wipe out life far beyond the area of direct impact?

32. Photosynthesis
Two stages:

33. Light-dependent Reactions
require light to work

34. smoke and soot

35. smoke and soot

36. smoke and soot

37. Light-independent Reactions
do not require light

38. Two Steps in Photosynthesis
sunlight
H2O O2
CO2
Where the two stages of photosynthesis occur inside the chloroplast
NADPH, ATP
light-dependent reactions
light-independent reactions
NADP+, ADP
sugars

39. Photosynthesis: Light-inDependent
Calvin Cycle
whether or not light is present.
Occur in the stroma

40. Light-inDependent
take the energy from ATP + energized ions from NADPH + carbon dioxide to make glucose or sugar.
carbon dioxide into CH2O.

41. Photosynthesis: Light-inDependent

42. Summary of Photosynthesis
sunlight
Light
Dependent
Reactions
12H2O
6O2
ATP
ADP + Pi
NADPH
NADP+
6CO2
Light
Independent
Reactions
Calvin-
Benson
cycle
6 RuBP
12 PGAL
6H2O P
phosphorylated glucose
end products (e.g., sucrose, starch, cellulose)

43. Photosynthesis: Light-inDependent

46. C3 Plants

49. C4 Plants

53. CAM Plants

56. Factors that Affect Rates
3 factors can limit the speed of photosynthesis: light intensity, CO2 concentration, temperature
Without enough light, a plant cannot photosynthesize very quickly, even if there is plenty of water and CO2 .

57. Factors that Affect Rates
Sometimes photosynthesis is limited by the concentration of carbon dioxide in the air.
Even if there is plenty of light, a plant cannot photosynthesize if there is insufficient carbon dioxide.

58. Factors that Affect Rates
If it gets too cold, the rate of photosynthesis will decrease. Plants cannot photosynthesize if it gets too hot.

59. Linked Processes Photosynthesis Aerobic Respiration
Energy-storing pathway
Releases oxygen
Requires carbon dioxide
Aerobic Respiration
Energy-releasing pathway
Requires oxygen
Releases carbon dioxide

60. Photosynthesis: The Movie
Animation
Movie