1. Photosynthesis Done by Bacteria, protists (algae), plants
Done by Bacteria, protists (algae), plants

2. Photoautotrophs do psyn.
Photo = light
Auto = self
Troph = feeder
Photo…..energy provided by light
Autotroph get own carbon from inorganic source (feed themselves)
Chemoautotroph…

3. Light Dependent reactions... Be able to draw and explain
Photosystem
Photolysis
Electron transport
Chemiosmosis
Location in chloroplast

4. Light Independent Reaction – Be able to explain….
Carbon fixation - atmospheric CO2, RUBP, Rubisco, unstable 6-C intermediate, PGA
Calvin Cycle – ATP used for…NADPH used for, what returns to light rxn, substrate level phosphorylation, 6 concurent cycles merge products to form 1 glucose
Know where in cell these rxns occur

5. Light Reactions Begin at Photosystem II – chlorophyll a =p680
Light-harvesting complex – surrounding complex of proteins and pigments
chlorophyll a, chlorophyll b, carotenoids
pass energy along to reaction center
Reaction center: holds 2 special chlorophyll a molecules and primary e-acceptor protein
e- jumps out of chlorophyll a onto 1˚e- acceptor
chlorophyll a of photosystem II is now P680+

7. Step 2 light reaction -Photolysis
Photosystem II (p680)
More modern version PS w/ specialized enzyme
Enzyme splits water
e- from H replace those lost by p680+
H+ ions released into thylakoid space
O bonds to another O and diffuses out

8. Step 3 light reaction – electron transport
e - from p680+ chlorophyll a move down e- transport chain
Give energy to proton pumps
e- enter chlorophyll p700 in photosystem I
Re-energized e- from p700+ exit thylakoid
And are picked up by NADP+
(co-enzyme & e- carrier)
NADPH moves to Calvin cycle to provide
reducing power

9. Step 4 - light reaction = photophosphorylation
Proton pumps powered by e-transport chain
Pump H+ ions into center of thylakoid
H+ ions flow out of thylakoid space through
ATPase by facilitated diffusion
Energy of flowing H+ used by ATPase to make lots of ATP
ATP sent to Calvin cycle to provide energy for endergonic, anabolic reaction forming
glucose

10. Cyclic vs non-cyclic psyn

11. Light Independent Reactions
Use ATP to make glucose
Take place in the stroma
Require ATP and NADPH from light rxn
Require CO2 from atmosphere
Stroma is filled with thousands of enzymes
Hundreds of Calvin cycles are running simultaneously
For every 6 Calvin cycles 1 glucose is formed

12. 1 C6H12O6

13. Carbon Fixation
Atomospheric CO2 is ‘fixed’ (attached) to an organic molecule called RuBP
The enzyme Rubisco mediates this rxn
RuBP + CO2 forms unstable intermediate
Intermediate splits into 2 PGA (3 C each)

14. Calvin Cycle – PGAL formation
ATP from light rxn gives a phosphate group to each PGA via substrate level phosphorylation
so… ATP phosphorylate PGA priming them to react
NADPH reduces each PGA (adding H to them) making them into PGAL (Pi is released)
(PGAL = G3P)

15. Calvin Cycle –reformation of RuBP
2 of the 12 PGAL are spit out of the cycle and made into glucose
The remaining PGAL are reformed into RuBP using energy from more ATP
Most glucose is converted to sucrose for transport or into starch for storage

16. ADP, Pi and NADP+ Return to Light dependent reaction

17. Photosynthesis Chemical Equation
6 CO H2O  C6H12O6 + 6 O2 + 6 H2O
Or with net water shown:
6 CO2 + 6 H2O  C6H12O6 + 6 O2

18. Evolution of Photosynthesis
1st photosynthetic bacteria did cyclic psyn
Only makes ATP not sugar
Still used by many bacteria

20. Evolution of PS II Non-cyclic psyn because e- obtained from H2O
(not recycled)
Allowed production of high energy carbs
A way to transport & store chemical energy
Allowed larger more complex organisms
All plants and some bacteria have PS II and do non-cyclic psyn

21. Chloroplast Location in plant
Any green part, most in leaves (p157)
A - cuticle (wax)
B - epithelial cell
C - palisade mesophyll
D - spongy mesophyll
E - stoma stomata

22. The Move to Land Waxy cuticle to prevent dehydration
Stomata – open & close to let in CO2
Water evaporates when stomata open
Closing stomata causes O2 CO2
Rubisco starts binding to O2
Puts O2 into Calvin cycle
Called photorespiration = bad, less glucose
Most plants do this….called C3 plants

23. C4 plants avoid photorespiration
Close stomata but keep CO2 levels near rubisco high by doing C4 cycle in mesophyll cells
In C4 cycle carbon fixation binds CO2 to PEP instead of RuBP
The enzyme binds CO2 to PEP ignores O2
PEP + CO2 = oxaloacetate ( a 4C molecule)
Oxaloacetate converts to malate which is sent
through plasmodesmata to bundle sheath cells

26. Malate drops off CO2 to rubisco in bundle sheath cells that run C3 Calvin cycle

27. CAM plants…cacti & desert plants
fix carbon by C4 cycle only at night
Store malate until day time
Close stomata and us malate as CO2 source to run Calvin cycle in day time when ATP and NADPH become available

28. Photoprotective pigments
Carotenoids absorb violet and blue-green light
Also protect the leaf from excessive light
Very similar to the carotenoids that protect the human eye