1. PHOTOSYNTHESIS
YouTube - Photosynthesis Song

2. 6CO2 + 6H2O  C6H12O6 + 6O2 Part I Photosynthesis
An anabolic (synthesize from smaller molecules),
endergonic (energy absorbing),
CO2 requiring process
uses light energy (photons) and H2O
produces organic macromolecules (glucose).
6CO H2O  C6H12O O2 3
glucose
SUN
photons

3. All Together Now Light Dependent Light InDependent Name this process!
PS II
PS I

4. Question:
Where does photosynthesis take place?

5. In Plants and Cyanobacteria
Autotrophs: self-producers.
Important Areas in/on leaves
a. stoma
b. mesophyll cells 56
Mesophyll
Cell
Chloroplast
Stoma

7. Stomata (stoma)
Pores in a plant’s cuticle; H2O and gases exchanged between plant and atmosphere
Oxygen
(O2)
Guard Cell
Carbon Dioxide
(CO2)

8. Actual Stoma
Guard
Cell

9. Stoma

10. Actual Leaf X-section
Mesophyll
Cells
Guard Cell

11. Mesophyll Cell
Nucleus
Cell Wall
Chloroplast
Central Vacuole

12. Sci league

13. Chloroplast Inner Membranes

14. Photosynthesis Reactions
O Light Dependent
- Takes place in Thylakoid
- Requires Light Energy
O Light Independent (Dark/C3)
- Takes place in stroma
- Does not require light energy

15. Question:
Why are plants green?

16. Because of; Chlorophyll Molecules
In thylakoid membranes.
Chlorophyll has Mg+ in the center.(see handout)
Chlorophyll pigments absorb certain wavelengths (blue and red are most important).
Plants are green because the green wavelength is reflected, not absorbed.

17. Pigment Structure

18. Wavelength of Light (um)
(short) V I B G Y O R (long)
High Energy
Low Energy

20. Absorption of Chlorophyll
violet blue green yellow orange red
Absorption
Short Wavelength long

21. Engleman’s Experiment:
Can you figure it out?
What did he learn?

22. Question:
During the fall, what causes the leaves to change colors?

23. Fall Colors Accessory pigments present.
During Fall, chlorophyll pigments are reduced (destroyed) revealing other pigments.
Carotenoids are pigments that are either red or yellow.

26. Part II Light Dependent Reactions
1. Two main parts (photosystems I & II).
2. PSII Produces ATP and
PSI Produces NADPH.
(energy carrying molecules)
They are used and then recycled as ADP and NADP+
ATP  ADP P energy
NADPH  NADP + energy H+

27. Light Independent Reactions
o Calvin Cycle; also called;
Light Independent Reaction or
C3 Cycle
o ATP and NADPH from Light Dependent
o Makes 3C glucose (carbs)

28. Light Dependent Reaction (Electron Flow)
Occurs in the Thylakoid membranes
Light reaction has two possible routes for electron flow.
A. Cyclic Electron Flow
B. Noncyclic Electron Flow

29. Cyclic electron flow
Once in a while, an excited electron from PSI's primary electron acceptor will "short circuit" and pop over to Fd and back into the electron transport chain between PSII and PSI, instead of to NADP+ reductase.
This will produce more ATP (and is a good supplement), but no NADP-H.
It's probably an accident of the proximity of the various molecules, but because it's not deleterious there has been no selection pressure against it. It just happens.

30. Cyclic Electron Flow P Occurs in thylakoid membrane
(primitive autotrophs: ____________ )
Photosystem I only
No O2 produced
P700 reaction center
Uses ETC
Generates ATP only
ADP ATP
7/8 P
(Energy + enzyme)

32. Cyclic Electron Flow SUN ATP e- produced by ETC Photons Photosystem I
Primary
Electron
Acceptor e-
ATP
produced
by ETC
Photosystem I
Accessory
Pigments
SUN
Photons

33. Overall Dependent Non Cyclic Reactions
(Z scheme)
P700
Chemiosmosis
Photosystem I
P680
Animation
Animation
Animation
Photosystem II

34. Noncyclic Electron Flow
Thylakoid membrane
PS II and PS I
P680 rxn center (PSII) - chlorophyll a
P700 rxn center (PS I) - chlorophyll a
Uses Electron Transport Chain (ETC)
Generates O2, ATP and NADPH

35. Noncyclic Electron Flow
ADP +  ATP
NADP+ + H  NADPH
O2 from splitting of H2O, not CO2
H2O  /2 O2 + 2H+ P
(Reduced)
(Reduced)
(Oxidized)

36. Oxidation / Reduction Oxidation: Reduction:
Is the loss of electrons/H in a reaction
Reduction:
Is the gain of electrons/H in a reaction

37. Chemiosmosis
H+ ion conc. Builds up in stroma (fluid) from H2O breakdown
ETC potential energy pumps more protons (H+) into thylakoids to help build up gradient
Powers ATP synthesis.
Thylakoid membranes.
ETC and ATP synthase (enzyme) make ATP.
Phosphorylation: phosphate plus ADP make ATP.

38. PSII: (Chemiosmosis) 1. 2. ATPsynthase
e- loses energy down ETC; pumps protons into thylakoid 1. 2.
2H2O  O2 + 4H+ + e-
ATPsynthase

39. PSII (Chemiosmosis) Phosphorylation (ATP making) High H+ concentration
Low H+ concentration

40. Final Analysis Light Dependent Reactions
1. Requires Light Energy
2. Products are;
o ATP (energy molecule)
o NADPH (energy molecule)
o Free Oxygen O2 3

42. Light Dependent / Independent Reactions
PER 10

43. Part III Calvin Cycle
Light Independent Rxn / C3
Carbon Fixation: Carbon from CO2 and built into larger carbon compounds (glucose)
Takes place in the Stroma
Uses ATP and NADPH from _____?_____.
Produces glucose: Takes 6 turns and uses 18 ATP and 12 NADPH.

44. Calvin Cycle (C3) 30C 36C 6C Start Animation (RuBisco)
(Ribulose Biphosphate)
(Phosphoglyceric Acid)
Period 1 7/8
PGAL synth
And 10 PGAL
PGAL
(Phosphoglyceraldehyde) PGAL 6C
2 PGAL available
Start Animation

45. 3
Carbon Fixation
(RuBisCO) 3
RBP 6
PGA 5
PGAL 6
PGAL 1
PGAL

46. Review
Photosystems Review
Calvin Benson Cycle Review

48. Photosynthesis + + H2O CO2 Energy Calvin Cycle Chloroplast O2 C6H12O6
ATP and
NADPH2
Which splits
water
Light is Adsorbed By
Chlorophyll
Calvin Cycle
ADP
NADP
Chloroplast
Used Energy and is recycled. O2 +
C6H12O6
Light Dependent
Light Independent

49. Part IV Plant Adaptations
C3 Plants
Control of water loss big problem for
plants (dehydration with stoma open)
C3 plants form 3-C compound
Ex. Soybeans, wheat, rice, oats
Have problems in dry weather
Closed stoma means no CO2 for Calvin Cycle

50. Plant adaptations C4 plants (Hatch-Slack cycle )
Takes CO2 in during day (stoma partially closed)
Saves as 4C. Uses enzyme PEPC: (phosphoenolpyruvate carboxylase)
Examples: (corn, crabgrass)
Can release CO2 to Calvin Cycle while stoma is closed
Conserves water while making sugar

51. C4 Cycle

52. Plant adaptations CAM plants (Crassulacean Acid Metabolism)
Stoma closed during day (limits H2O loss)
succulents (cactus)
Takes in CO2 at night for use during daytime
CO2 released to Calvin Cycle during day

53. CAM Night Time Stomata open. CO2 taken in (very little water lost)
CO2 is fixed by PEPCase
Stored in form of malic acid.

54. CAM Day Time Stomata close.
CO2 removed from malic acid & added to RuBP
Now do Calvin Cycle

55. CAM Plants Night (Stomates Open) Day (Stomates Closed) Vacuole C-C-C-C
Malate
CO2 C3
C-C-C
Pyruvic acid
ATP
PEP
glucose

56. Final Conclusions
1. CO2 source of most organic molecules on earth.
Light reactions provide (ATP) and (NADPH) to
make Organic Compounds.
3. Chemiosmosis makes ATP in ETC.
Calvin Cycle fixes C into organic molecules per
cycle.
5. End result of Calvin cycle is 3 C sugar.

57. More Final Conclusions
Rubisco most important protein on earth.
CO2 diffuse into stomata; H2O diffuses out.
C4 & CAM plants use PEP to fix Carbon.
CAM plants store CO2 at night
(cool & humid)

58. What do plants and heterotrophs do with glucose made in photosynthsis?
Source of energy!
Energy retrieved by the process of Cellular Respiration
Takes place in the mitochondria

59. Respiration & Photosynthesis