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

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Presentation on theme: "The Calvin Cycle Fixing Carbon Dioxide into Organic Compounds which can be used for storage and structure."— Presentation transcript:

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

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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

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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!


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