1. The Light-Independent Reactions (Dark Reactions) Chapter 10 10.3 Pgs. 198-199 BUT FIRST! A review of yesterday’s Light-Dependent Reactions: Photosystems and ETC Objective: I can describe and count the overall number of reactants and products involved in the Calvin Cycle while being able to analyze a document with details of the process. Will need to know names of some enzymes/molecules

2. Review of Light Reactions  Photon of light hits and is absorbed by a pigment (only absorbs certain wavelengths) in the photosystem: (light-harvesting protein complex in thylakoid membrane)  For plants, photosystem II happens 1 st  Pigment molecule is energized and passes excitation energy to other pigments in the photosystem  Eventually, excitation energy reaches the reaction center: made of 2 chlorophyll a pigment molecules (PS II = P680)

3. Review of Light Reactions  Reaction center releases electron  Reaction center (PSII) replaces electron by an enzyme that splits water  Water consumed, Oxygen produced  Released electron goes to a primary electron acceptor (within PSII)  Taken to the 1 st electron transport chain via carrier molecules  Passes through a proton pump (protein)  Protons pumped into thylakoid, creating a concentration gradient (proton-motive force)

4. Review of Light Reactions  Protons return by diffusion to stroma through ATP synthase  ATP is made  Electron at end of 1 st ETC enters Photosystem I…why?  Photosystem I lost electron when its pigments hit with photons, causing excitation energy to pass resulting in a PSI’s reaction center losing electron  PSI’s electron goes to 2 nd ETC (via primary electron acceptor and carrier molecules)  this ETC make ATP?  NO

5. Review of Light Reactions  Electron ends up in an enzyme called NADP + reductase  Electron and hydrogen given to NADP + turning it into NADPH (reduction)  Summary: Light Reactions  Consumed water  Produced oxygen (by-product)  Produced ATP and NADPH  To power and run the Calvin Cycle  Provide energy + reducing power…

6. Calvin Cycle – General Facts  2 nd and Last stage in photosynthesis  Occurs in Stroma of Chloroplast  ATP + NADPH (from light rxns) power it  Main reactant: CO 2  how many? 6  Main product: glucose (C 6 H 12 O 6 )  The cycle turns 6 times  With Calvin Cycle in reg. plants, ENTIRE process is a type of C 3 photosynthesis  Because main output molecule made has 3 carbons  Glyceraldehyde-3-phosphate (G3P)

8. Calvin Cycle – Detailed Facts (you need to know)  6 enzyme-catalyzed reactions in a cycle (6 steps)  Will break down into 3 steps 1) Carbon fixation attach carbon atom from gas to organic molecule CO 2 bonds with 5-carbon molecule called RuBP already in cycle (catalyzed by RuBisCO) Forms unstable intermediate 6-carbon molecule, which rapidly… breaks down into two 3-carbon molecules PGA

9. Calvin Cycle – Detailed Facts (you need to know) 2) Reduction ATP gives energy to… NADPH reduces… each 3-carbon molecule In order to have cycle (return to RuBP), must turn cycle more times Only 2 of the 12 (twelve) 3-carbon molecules (G3P) combine to make glucose (6 carbons) 2 2 Cycle turns 6 times Need 6 CO 2 There are 6 C in glucose 6 6 12 10 *Gasp* Can make glucose!? (phosphorylates)  Glyceraldehyde-3-phosphate (G3P) PGA G3P

10. Calvin Cycle – Detailed Facts (you need to know) 3) Regeneration 10 other G3P’s energized and rearranged to make original 6 RuBP Numbers work out: G3P: 10 X 3 = 30 RuBP: 6 X 5 = 30 Allows Cycle to continue 6 10 To make each RuBP, requires 1 ATP, so… 6

11. Calvin Cycle – Picture Overview

12. Calvin Cycle Summary  Breathe in 6 CO 2  Bonds with 6 RuBP (catalyzed by RuBisCO) to make 12 intermediate 3-carbon molecules (PGA)  Energize/Phosphorylated by 12 ATP  Reduced by 12 NADPH  Makes 12 G3P molecules  2 will combine to make glucose  Other 10 will turn back into 6 RuBP by being energized by 6 ATP Totals CO 2 in6 ATP in18 NADPH in12 Glucose out 1 http://www.science.smith.edu/departments/Biology/Bio231/calvin.html http://www.youtube.com/watch?v=o1I33Dgcc_M http://highered.mheducation.com/sites/9834092339/student_view0/chapter39/calvin_cycle.html