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Photosynthesis: The Calvin Cycle Life from Air AP Biology 2006-2007 Whoops! Wrong Calvin… The Calvin Cycle AP Biology Remember what it means to be a plant… Need to produce all organic molecules necessary for growth carbohydrates, lipids, proteins, nucleic acids Need to store chemical energy (ATP) produced from light reactions in stable form can be moved around plant saved for a rainy day AP Biology Autotrophs Making energy & organic molecules from light energy photosynthesis carbon + water + energy glucose + oxygen dioxide 6CO2 + 6H2O + light C6H12O6 + 6O2 energy AP Biology Light reactions Convert solar energy to chemical energy ATP energy NADPH reducing power What can we do now? build stuff !! AP Biology How is that helpful? Want to make C6H12O6 synthesis How? From what? What raw materials are available? CO2 NADPH carbon fixation NADP C6H12O6 AP Biology reduce CO2 NADP From CO2 C6H12O6 CO2 has very little chemical energy fully oxidized C6H12O6 contains a lot of chemical energy reduced endergonic Reduction of CO2 C6H12O6 proceeds in many small uphill steps each catalyzed by specific enzyme using energy stored in ATP & NADPH AP Biology From Light reactions to Calvin cycle Calvin cycle chloroplast stroma Need products of light reactions to drive synthesis reactions ATP NADPH AP Biology C C Calvin cycle C C C C C 1C C C C C C 3. Regeneration C C C C C of RuBP RuBP starch, sucrose, cellulose & more ribulose bisphosphate 3 ADP used to make glucose C=C=C H H H | | | C–C–C AP Biology C C C C C C C C C C C C C C C C C C CO2 1. Carbon fixation C C C C C C 5C 3 ATP C Rubisco ribulose bisphosphate carboxylase C C C C C C 6C C C C C C C glyceraldehyde-3-P G3P 3C C C C PGA phosphoglycerate 6 NADP C C C C C C 6 ATP 2. Reduction 6 NADPH 3C C C C C C C 3C 6 ADP C C C C C C H | H | H | Remember G3P? glucose C-C-C-C-C-C 2 ATP 2 ADP glycolysis fructose-6P P-C-C-C-C-C-C-P DHAP G3P P-C-C-C C-C-C-P pyruvate AP Biology C-C-C 2 NAD+ 2 NADH 4 ADP 4 ATP Calvin Cycle Stroma of chloroplast Carbon dioxide (CO2) Rubisco Ribulose 1,5-bisphosphate (RuBP) (5C) 3-phosphoglycerate (3C) (PGA) Carbon fixation 3 ADP 6 ADP Reforming RuBP 3 ATP 1,3-bisphosphoglycerate (3C) 6 NADPH 2Pi Reverse of glycolysis Glyceraldehyde 3-phosphate (3C) Glucose and other sugars 6 NADP+ 6Pi Glyceraldehyde 3-phosphate (3C) (G3P) Glyceraldehyde 3-phosphate (3C) (G3P) AP Biology 6 ATP To G-3-P and Beyond! Glyceraldehyde-3-P end product of Calvin cycle energy rich 3 carbon sugar “C3 photosynthesis” G-3-P = important intermediate G-3-P glucose carbohydrates AP Biology lipids amino acids nucleic acids Rubisco Enzyme which fixes carbon from air ribulose bisphosphate carboxylase the most important enzyme in the world! it makes life out of air! AP Biology definitely the most abundant enzyme Accounting The accounting is complicated 3 turns of Calvin cycle = 1 G3P 3 CO2 1 G3P (3C) 6 turns of Calvin cycle = 1 C6H12O6 (6C) 6 CO2 1 C6H12O6 (6C) 18 ATP + 12 NADPH 1 C6H12O6 AP Biology any ATP left over from light reactions will be used elsewhere by the cell Photosynthesis summary Light reactions produced ATP produced NADPH consumed H2O produced O2 as byproduct Calvin cycle consumed CO2 produced G3P (sugar) regenerated ADP regenerated NADP AP Biology ADP NADP Summary of photosynthesis 6CO2 + 6H2O + light C6H12O6 + 6O2 energy Where did the CO2 come from? Where did the CO2 go? Where did the H2O come from? Where did the H2O go? Where did the energy come from? What’s the energy used for? What will the C6H12O6 be used for? Where did the O2 come from? Where will the O2 go? What else is involved…not listed in this equation? AP Biology Supporting a biosphere On global scale, photosynthesis is the most important process for the continuation of life on Earth each year photosynthesis synthesizes 160 billion tons of carbohydrate heterotrophs are dependent on plants as food source for fuel & raw materials AP Biology The poetic perspective… All the solid material of every plant was built by sunlight out of thin air All the solid material of every animal was built from plant material air AP Biology Then all the cats, dogs, rats, people & elephants… are really strands of air woven together by sunlight! sun Any Questions?? AP Biology 2006-2007