1. The Calvin Cycle
Fixing Carbon Dioxide into Organic Compounds which can be used for storage and structure

2. Small Recap Figure 10.5 H2O CO2 [CH2O] O2 (sugar) Light
LIGHT REACTIONS
CALVIN
CYCLE
Chloroplast
[CH2O]
(sugar)
NADPH
NADP 
ADP
+ P O2
Figure 10.5
ATP

3. But before we start!! Review

4. Colors? Gamma rays X-rays UV Infrared Micro- waves Radio 10–5 nm
380
450
500
550
600
650
700
750 nm
Visible light
Shorter wavelength
Higher energy
Longer wavelength
Lower energy

5. What’s up with colors? Light Reflected Chloroplast Absorbed Granum
Transmitted

6. Electron transport chain
The whole she bang!
Photosystem II
(PS II)
Photosystem-I
(PS I)
ATP
NADPH
NADP+
ADP
CALVIN
CYCLE
CO2
H2O O2
[CH2O] (sugar)
LIGHT
REACTIONS
Light
Primary
acceptor Pq
Cytochrome
complex PC e
P680 e– +
2 H+ Fd
reductase
Electron
Transport
chain
Electron transport chain
P700
+ 2 H+
+ H+

7. How to get excited  what’s missing?
state
Energy of election
Heat
Photon
(fluorescence)
Chlorophyll
molecule
Ground e–

8. Engrish Translation? Figure 10.14 NADPH e– Mill makes ATP Photon
Photosystem II
Photosystem I
NADPH
Figure 10.14 

9. Two Thumbs Up! Awesome! We all got it Mr. V!!
GOOD!!!!
Off to the Calvin Cycle

11. The Big Picture
The Calvin Cycle functions to fix inorganic carbon (Carbon Dioxide) into organic compounds (sugars).
This process requires energy – the ATP and NADPH made during the light reactions.

12. Lots of little steps…
There are many little steps in the Calvin Cycle, but we’ll concern ourselves with a few main phases:
Phase I: Carbon Fixation (putting on Carbons)
Phase II: Reduction (Gaining of electrons)
Phase III: Regeneration

13. Carbon Fixation
Carbon Dioxide is brought into the cycle and fixed by the enzyme rubisco.
Rubisco fixes CO2 into a compound called Ribulose bisphosphate (RuBP) (5 carbons each), resulting in 2 molecules of phosphoglycerates (3 carbons each)

14. Reduction
This is where the energy (electrons) from the light reactions comes back in the form of ATP and NADPH.
NADPH comes in and reduces the intermediate compounds resulting in formation of G3Ps. Here a molecule of G3P exits the cycle (the net product) and the rest continues to the regeneration phase.

15. Regeneration
This phase serves to reform RuBP which will be used in the next turning of the cycle.
This step requires ATP

16. Phase 1: Carbon fixation
(G3P)
Input
(Entering one
at a time)
CO2 3
Rubisco
Short-lived intermediate
3 P P
Ribulose bisphosphate (RuBP)
3-Phosphoglycerate
6 P 6
1,3-Bisphoglycerate
6 NADPH
6 NADPH+
Glyceraldehyde-3-phosphate
6 ATP
ATP
3 ADP
CALVIN
CYCLE 5 1
G3P (a sugar) Output
Light
H2O
LIGHT REACTION
ATP
NADPH
NADP+
ADP
[CH2O] (sugar)
CALVIN CYCLE O2
6 ADP
Glucose and other organic compounds
Phase 1: Carbon fixation
Phase 3: Regeneration of the CO2 acceptor (RuBP)
Phase 2: Reduction

17. The lowdown
Basically, know the calvin cycle in the same level of detail as the Krebs cycle. Don’t worry about specific details. But definitely know:
RuBP
Rubisco
G3P
Amounts of CO2, ATP, and NADPH

18. A problem with photosynthesis
To get carbon dioxide into their cells, plants have to open themselves up to the air. This is problematic.
Q: Why?

19. Stomata
Stomata are the pores that let in CO2 and let out O2. They are composed of two ‘guard cells’ that form a mouth like structure. ‘Stoma’ means ‘mouth’…
On hot, dry days plants close their stomata.

20. Mo closed stomata, mo problems
When stomata are closed, what is going to happen?

21. A waste of good carbon
When CO2 decreases, and O2 increases, rubisco will begin fixing O2. This is because it is a mild oxygenase as well as a carboxylase.
This produces a ‘waste’ product which splits and is exported out of the chloroplast.
Basically, carbon is being stripped out of the calvin cycle

23. Why would rubsico betray us so?
The theory is that rubsico is a remnant of a pre-oxygenated environment. If there wasn’t any oxygen around, then photorespiration wouldn’t have been a problem. It ‘discovered’ its oxygenase after the fact…

24. How does that plant solve the problem of photorespiration?
You’ll have to wait!!
Can you contain yourself…we’ll see.
Maybe you can read about it!