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C4 versus C3 plants Using ATP and NADPH to generate high energy containing covalent bonds PGA: phosphoglyceric acid PGAL: phosphoglyceraldehyde (CO2 from the air) stroma H 2O Carbon dioxide fixation rubisco P H H C C OH H C O (RuBP) (intermediates) (PGA) ADP O cyclic production of intermediate sugar phosphates ATP + NADPH ADP Pi NADP+ (PGAL) Pi (PGAL) sugar phosphate synthesis sugar phosphate Low energy electrons H Calvin cycle PGA typically used at once to form carbohydrates (mainly sucrose, starch, cellulose) Fig. 10-9, p. 157 P H H C C OH PGAL H C H O High energy electrons The C4 pathway concentrates CO2 C4 cycle Interaction between the C4 cycle and the C3 cycle AMP mesophyll cells C3 cycle bundle sheath cells Fig. 10-12, p. 159 The C4 pathway concentrates CO2 air space guard cell bundle sheath cell CO2 movement upper epidermis In C4 plants, CO2 is first captured by PEP carboxylase in mesophyll cells to make oxaloacetate which is subsequently turned into malate. This malate then diffuses into the chloroplasts of bundle sheath cells where it releases CO2. Thus, bundle sheath chloroplasts contain higher CO2 concentrations compared to chloroplasts in mesophyll cells and therefore have higher photosynthesis and lower photorespiration rates. mesophyll cells vascular bundle lower epidermis Fig. 10-11, p. 159 Where/when is it used/made? Overall Photosynthesis Reaction 6CO2 + 6H2O + energy C6H12O6 + 6O2 24 C-O bonds + 12 H-O bonds 36 covalent bonds 7 C-O bonds + 5 C-C bonds + 7 C-H bonds + 5 H-O bonds + 12 O-O bonds 36 covalent bonds oxygen released sunlight energy photosystem II e− H+ H2O is split H+ lumen (H+ reservoir) H+ NADP+ H+ electron transport system H+ Stroma Lightdependent reactions photosystem I e− ADP + Pi electron transport system sugar phosphate carbon dioxide used Lightindependent reactions carbohydrate end product (e.g. sucrose, starch, cellulose) Fig. 10-3, p. 151 Overall Respiration Reaction C6H12O6 + 6O2 6CO2 + 6H2O + energy 7 C-O bonds + 5 C-C bonds + 7 C-H bonds + 5 H-O bonds + 12 O-O bonds 36 covalent bonds 24 C-O bonds + 12 H-O bonds 36 covalent bonds Cytoplasm energy Input(ATP) Overview of respiration steps glucose Glycolysis 2 ATP (net) 2 NADH 2 pyruvate 2 CO2 2 NADH 6 NADH 2 FADH2 TCA Cycle 4 CO2 2 ATP water Electron transport chain phosphorylation Mitochondrion 34 ATP oxygen Fig. 9-5, p. 138 pyruvate from cytoplasm inner membrane H+ Coenzymes give up electrons, hydrogen (H+) to transport system NADH acetyl-CoA NADH TCA cycle e− e− H+ H+ FADH2 As electrons pass through system, H+ is pumped out from matrix carbon dioxide 2 ATP Pi ADP ATP synthesized e− Oxygen accepts electrons, joins with 2H+, forms water oxygen H+ H+ MATRIX electron transport system H+ H+ flows in H+ INTERMEMBRANE space Fig. 9-8c, p. 142 Comparison Chloroplasts and mitochondria • In common: - membrane localized ATP synthase - H+ concentration difference - electron transport chain - DNA - Bacterial origin • Differences: – – – – – NADH versus NADPH One versus two outer membranes O2 production versus consumption CO2 consumption versus production Production of energy carriers to promote uphill reactions in general – Production of energy carriers to allow C-C and C-H bond formation What is needed to proceed ? Cytoplasm energy Input(ATP) Overview of respiration steps glucose Glycolysis 2 ATP (net) 2 NADH 2 pyruvate 2 CO2 2 NADH 6 NADH 2 FADH2 TCA Cycle 4 CO2 2 ATP water Electron transport chain phosphorylation Mitochondrion 34 ATP oxygen Fig. 9-5, p. 138 General overview: Making ATP from starch Electron transport system STARCH (Glucose multimer) 6 O2 + 24 H+ Digestion Glucose (6C) Glycolysis 2 ADP + 2 iP + 2 NAD+ 6 + 2 + 2 NAD+ + 2 FAD + 12 H2O + H+ gradient 2 Pyruvate (3C) +2 ATP + 2 NADH Entry into TCA CoASH + 2 NAD+ 2 Acetyl-CoA (2C) + 2 CO2 + 2 NADH TCA 2 ADP + 2 iP + 6 NAD+ + 2FAD + 6 H2O 2 (2CO2 + ATP + 3NADH + FADH2) Chemiosmosis 34 ADP + 34 iP 6X3 + 2X3 + 2X3 + 2X2 34 ATP potential to transfer electrons (measured in volts) NONCYCLIC ELECTRON TRANSPORT P700* -0.6 e− sunlight energy P680* e− NADP H e− 0 sunlight energy e− +0.4 H+ + NADP+ ADP + Pi e− P700 photosystem I +0.8 photosystem II Pigments from the light harvesting complex released energy used to form ATP from ADP and phosphate e− H2O photolysis P680: reaction center of photosystem II P700: reaction center of photosystem I Fig. 10-7, p. 154 potential to transfer electrons (measured in vo CYCLIC ELECTRON TRANSPORT P700* -0.6 e− sunlight energy NADPH P680* e− e− 0 sunlight energy e− +0. 4 H+ + NADP+ ADP + Pi e− P700 photosystem I +0. 8 photosystem II released energy used to form ATP from ADP and phosphate e− H2O photolysis Fig. 10-7, p. 154 Using ATP and NADPH to generate high energy containing covalent bonds PGA: phosphoglyceric acid PGAL: phosphoglyceraldehyde (CO2 from the air) stroma H 2O Carbon dioxide fixation rubisco P H H C C OH H C O (RuBP) (intermediates) (PGA) ADP O cyclic production of intermediate sugar phosphates ATP + NADPH ADP Pi NADP+ (PGAL) Pi (PGAL) sugar phosphate synthesis sugar phosphate Low energy electrons H Calvin cycle PGA typically used at once to form carbohydrates (mainly sucrose, starch, cellulose) Fig. 10-9, p. 157 P H H C C OH PGAL H C H O High energy electrons What is (are) the final result (s)? Cytoplasm energy Input(ATP) Overview of respiration steps glucose Glycolysis 2 ATP (net) 2 NADH 2 pyruvate 2 CO2 2 NADH 6 NADH 2 FADH2 TCA Cycle 4 CO2 2 ATP water Electron transport chain phosphorylation Mitochondrion 34 ATP oxygen Fig. 9-5, p. 138 potential to transfer electrons (measured in volts) NONCYCLIC ELECTRON TRANSPORT P700* -0.6 e− sunlight energy P680* e− NADP H e− 0 sunlight energy e− +0.4 H+ + NADP+ ADP + Pi e− P700 photosystem I +0.8 photosystem II Pigments from the light harvesting complex released energy used to form ATP from ADP and phosphate e− H2O photolysis P680: reaction center of photosystem II P700: reaction center of photosystem I Fig. 10-7, p. 154 potential to transfer electrons (measured in vo CYCLIC ELECTRON TRANSPORT P700* -0.6 e− sunlight energy NADPH P680* e− e− 0 sunlight energy e− +0. 4 H+ + NADP+ ADP + Pi e− P700 photosystem I +0. 8 photosystem II released energy used to form ATP from ADP and phosphate e− H2O photolysis Fig. 10-7, p. 154 Division of Labor in Chloroplasts Green thylakoids • Capture light • Liberate O2 from H2O • Form ATP from ADP and phosphate • Reduce NADP+ to NADPH Colorless stroma • Contains water-soluble enzymes • Captures CO2 • Uses energy from ATP and NADPH for sugar synthesis Light reactions Dark reactions Where/when are energy carriers (ATP, NADH and NADPH) needed and where/when are they produced? Electron donors & Final electron acceptors? pyruvate from cytoplasm inner membrane H+ Coenzymes give up electrons, hydrogen (H+) to transport system NADH acetyl-CoA NADH TCA cycle e− e− H+ H+ FADH2 As electrons pass through system, H+ is pumped out from matrix carbon dioxide 2 ATP Pi ADP ATP synthesized e− Oxygen accepts electrons, joins with 2H+, forms water oxygen H+ H+ MATRIX electron transport system H+ H+ flows in H+ INTERMEMBRANE space Fig. 9-8c, p. 142 potential to transfer electrons (measured in volts) NONCYCLIC ELECTRON TRANSPORT P700* -0.6 e− sunlight energy P680* e− NADP H e− 0 sunlight energy e− +0.4 H+ + NADP+ ADP + Pi e− P700 photosystem I +0.8 photosystem II Pigments from the light harvesting complex released energy used to form ATP from ADP and phosphate e− H2O photolysis P680: reaction center of photosystem II P700: reaction center of photosystem I Fig. 10-7, p. 154 Other (very) important things… Absorption spectra of Chlorophyll a and b Percent of light absorbed 100 80 chlorophyll b 60 chlorophyll a 40 20 0 400 500 600 Wavelength (nm) 700 Fig. 10-5, p. 152 Twelve Most Common Elements in Living Organisms Element Symbol Number of Protons Hydrogen H 1 Carbon C 6 Nitrogen N 7 Oxygen O 8 Sodium Na 11 Magnesium Mg 12 Phosphorus P 15 Sulfur S 16 Chlorine Cl 17 Potassium K 19 Calcium Ca 20 Iron Fe 26