1. PHOTOSYNTHESIS THREE PHASE REACTION
LIGHT ABSORBTION (CHLOROPHYLL)
LIGHT REACTION (LIGHT DEPENDENT)
DARK REACTION (LIGHT INDEPENDENT)

2. Green Plants and Photosynthesis
All of our food ultimately results from the process of photosynthesis
in green plants and algae. The pigment chlorophyll is responsible for
the green color of plants as well as their ability to photosynthesize.
In common terrestrial plants photosynthesis is usually carried out in
the leaves, although it can also occur in the stem or other parts of the
plant.
Dr. C.E. Jeffree, Oxford Scientific Films

3. PHOTOSYNTHESIS NET REACTION
SUNLIGHT
6 CO H20
C6H12O O2
CHLOROPHYLL
PHOTOSYNTHESIS ACTUAL REACTION
SUNLIGHT
6 CO H20
C6H12O O H2O
CHLOROPHYLL
DISCOVERED THROUGH THE USE OF O-18 TAGGED WATER

4. LIGHT ABSORBTION BY CHLOROPHYLL
CHLOROPHYLL A IS THE PRIMARY PHOTOSYNTHETIC PIGMENT
CHLOROPHYLL B, CAROTENE, PHYCOBILINS, XANTHROPHYLL, AND OTHER PIGMENTS ARE ACCESSORY PIGMENTS
LOCATED IN THYLAKOID MEMBRANE OF THE CHLOROPLAST
ABSORBS RED AND BLUE LIGHT, REFLECTS GREEN LIGHT
ACCESSORY PIGMENTS TRAP GREEN AND YELLOW LIGHT AND TRANSFER IT TO CHLOROPHYLL A (allow greater use of available energy)

5. Chlorophyll a absorption and efficiency of Photosynthesis

6. STRUCTURE OF CHLOROPLAST
GRANA ARRANGED IN STACKS TO MAXIMIZE EXPOSURE TO LIGHT - LIGHT REACTIONS OCCUR HERE.
SHAPE OF GRANA MAXIMIZES SURFACE AREA FOR PHOTOSYNTHESIS
GRANA SURROUNDED BY STROMA - PERMITS EASY DIFFUSION OF PHOTOSYNTHETIC PRODUCTS
PRODUCTS MOVE BACK AND FORTH BETWEEN THE LUMEN AND THE STROMA
STROMA IS A PROTEIN RICH SOLUTION IN WHICH DARK REACTIONS OCCUR

7. Chloroplast Structure

8. CHLOROPLAST STRUCTURE
THYLAKOIDS
GRANA
STROMA
CHLOROPLAST MEMBRANE

9. Chloroplasts in Onion Root CellsChloroplasts are minute, green, spherical structures that are essential to the process of photosynthesis. The chlorophyll molecule, a very complex organic molecule composed primarily of magnesium, carbon, and hydrogen, regulates the absorption of the red, violet, and blue portions of the visible light spectrum. Richard Kirby, Oxford Scientific Films

10. LIGHT REACTIONS TWO PARTS
CONVERSION OF SUNLIGHT TO ELECTRICAL ENERGY (ELECTRON TRANSPORT)
ELECTRICAL ENERGY IS THEN CONVERTED TO CHEMICAL ENERGY STORED IN BONDS

11. PHOTOSYSTEM II
LIGHT STRIKES CHLOROPHYLL - ELECTRONS ABSORB PHOTON OF LIGHT ENERGY AND BECOME “EXCITED”
“EXCITED” ELECTRONS MOVE TO ELECTRON ACCEPTORS WHERE THEY MOVE TO A LOWER ENERGY STATE (ELECTRON TRANSPORT CHAIN) TRANSFERED TO PHOTOSYSTEM I

12. PHOTOSYSTEM I
LIGHT ALSO STRIKES CHLOROPHYLL IN PHOTOSYSTEM I WHICH ALSO MOVE ALONG AN ELECTRON TRANSPORT CHAIN
ELECTRONS REPLACED BY THOSE FROM PHOTOSYSTEM II
ELECTRONS ARE PICKED UP BY NADP TO FORM NADP- - WATER IS SPLIT INTO TWO H+ IONS, TWO ELECTRONS, AND AN OXYGEN ATOM
The H + ions are used to reduce NADP to form NADPH2
The electrons go to photosystem II
The oxygen atom combines with another oxygen to form O2
NADPH2 goes to stroma to be used in DARK REACTIONS

13. PHOTOSYSTEM I e e e ELECTRON TRANSPORT CHAIN ATP - - - - - e - ATP SUN
ADP + P
SUN
cytochromes e - - e -
ELECTRON
ACCEPTORS e e - - e -
CHLOROPHYLL e
ELECTRON
TRANSPORT
CHAIN
ADP + P
ATP

14. PHOTOSYSTEM II NADPH2 O H20 ATP O2 NADP 2 H+ 2 e- ADP+ P --
ELECTRON TRANSPORT
CHAIN
2 H+
H20
2 e-
ADP+ P
ATP
CHLOROPHYLL II
CHLOROPHYLL I
ELECTRON TRANSPORT
CHAIN

15. Photosystem I and II

16. CHEMIOSMOSIS
DIFFUSION OF CHEMICALS THROUGH THE MEMBRANE RESULTING IN PRODUCTION OF ATP
ELECTRONS MOVE ALONG ELECTRON TRANSPORT CHAIN FROM HIGH TO LOW CONCENTRATION
CONCENTRATION OF HYDROGEN IONS IS HIGHER INSIDE THE LUMEN THAN IN THE STROMA
ELECTROCHEMICAL ENERGY IS GENERATED BY THE MOVEMENT OF IONS ACCROSS THE MEMBRANE
ENERGY IS USED TO PHOSPHORYLATE ADP TO FORM ATP (using ATP synthetase)
ATP IS THEN USED IN CARBON FIXATION IN DARK REACTIONS

17. DARK REACTIONSCALVIN CYCLE (C3)
DOES NOT REQIRE LIGHT ENERGY
USES ENERGY STORED IN LIGHT REACTIONS IN THE FORM OF ATP AND NADPH2
INVOLVES FIXATION OF CO2 INTO CARBON COMPOUNDS
OCCURS IN MOST PLANT SPECIES IN MODRATE CLIMATES
DIVIDED INTO FOUR BASIC STEPS

18. FOUR STAGES OF THE DARK REACTIONS
CO2 DIFFUSES INTO THE STROMA AND AN ENZYME IN THE THYLAKOID BINDS IT TO A 5-CARBON RDP (RuBP) FORMING AN UNSTABLE 6-CARBON MOLECULE
THIS 6-CARBON MOLECULE SPLITS TO FORM TWO 3- CARBON PGA MOLECULES
PGA IS CHANGED TO PGAL BY PHOSPHORYLATON USING ATP AND THE ADDITION OF H FROM NADPH2
TWO PGAL MOLECULES COMBINE TO FORM A 6- CARBON COMPOUND FDP (fructose diphosphate) WHICH EITHER IS CONVERTED INTO GLUCOSE (1 FOR EVERY 6 CO2 FIXED) OR USED TO REGENERATE RDP SO THE CYCLE CAN CONTINUE

19. CALVIN CYCLE (C3) CO2 PGA 3-C PGAL 6-C PGA 3-C PGAL RDP 5-C FDP 6-C
ATP
ADP
CO2
PGA
3-C
PGAL
NADPH NADP
6-C
ATP
ADP
PGA
3-C
PGAL
NADPH NADP
RDP 5-C
FDP 6-C
INTERMEDIATE
COMPOUNDS
ATP
RP 5-C
ADP
GLUCOSE