SUMMARY Photoassimilates are oxidized = Energy The value of RQ ~ oxidation state Starch => storage glucose=> Resp. Glycolysis => A net gain 2 or 3 ATP Hydrolytic = 4 ATP - 2 ATP Phosphorolytic = 4 ATP - 1 ATP Oxidative pentose phosphate ~ alternate pathway

The Oxidative Pentose Phosphate Pathway From Glycolysis Glucose - 6 - P NADP + NADPH 6 - Phosphogluconate NADP + CO 2 NADPH Ribulose - 5 - P Xylulose -5-P Ribose - 5 - P To Glycolysis Sedoheptulose -7-P Glyceraldehyde- 3 - P Fructose - 6 - P Erythrose-4-P Erythrose-4-P Erythrose-4-P

THE OXIDATIVE PENTOSE PHOSPHATE PATHWAY Alternate route ~ glucose => cytosol Tetrose + Pentose + NADPH The oxidation of glucose-6-P determines the balance Glycolysis - OPPP. Sensitive to the level of NADP + Second oxidation ( CO2 removed) = ribulose- 5 - P ( e - acceptor NADPH+) Products => glyceraldehyde - 3 - P + fructose - 6 - P ====> Glycolysis

THE OXIDATIVE PENTOSE PHOSPHATE PATHWAY Functions Generate reducing potential in the form of NADPH. It serves as an electron donor and drive biosynthetic reactions in the cytosol. The production of pentose phosphate, precursor for ribose and deoxyribose => nuclei acids. Erythrose-4-P precursor biosynthesis of aromatic aminoacids, lignin and flavonoids

The Fate of Pyruvate + O2 Acetaldehyde Lactate CO2 + H2O Ethanol Aerobic Anaerobic - Fermentation + O2 NADH PYRUVATE CO2 NAD + Mitochondrial Respiration Acetaldehyde NADH Lactate NAD + CO2 + H2O Ethanol

OUTLINE 2.3 Mitochondrion: Structure and Organization. 2.3.1 Citric Acid Cycle (CAC) 2.3.2 Electron transport chain 2.3.3 Alternate electron pathways 2.3.4 Gluconeogenesis

OXIDATIVE RESPIRATION THE MITOCHONDRION Outer membrane 0.5 m Cristae Inner membrane 2 m

The Citric Acid Cycle The oxidation of pyruvate to carbon dioxide Pyruvic Acid NAD + CoA-SH NADH CO 2 Acetyl-CoA Oxaloacetic Acid Citric Acid 9 Isocitric Acid Malic Acid 4 Fumaric acid - Ketoglutaric Acid 7 FADH2 Succinic Acid 5 ATP Succinyl- CoA

Summary Citric Acid Cycle Eight enzyme-catalyzed steps Acetyl-CoA + 4-carbon oxaloacetate => 6-carbon, tricarboxylic citric acid. Acetyl group degraded => 2CO2 Four oxidations => 3 NADH and FADH2 One molecule ATP Oxaloacetate is regenerated => allows the cycle to continue hexose sugar => turn twice

Oxidation of NADH and FADH2 ATP Synthase CI CIII CIV 2H+ 4H+ 2H+ Intermembrane space Cyt b UQ Cyt a Fo Inner FMN Cyt c Cyt c1 Cyt a3 F1 FAD 1/2 O2 + 2H+ Matrix ADP+Pi ATP NADH + H + H2O H+ CII

Summary Oxidation of NADH and FADH2 Electrons removed from substrate in the CAC are passed to O2 => mitochondrial electron transport chain. Four multiprotein complexes and mobile carriers C. four transfers electrons to O2 => H2O Proton gradient across the membrane is established. It is used to drive ATP synthesis

Alternate Electron Pathways in Plants At least two pathways are unique to plants External NADPH Dehydrogenase Skip complex I => only two ATP formed Rotenone-Insensitive NADH dehydrogenase => only one ATP Cyanide-resistant respiration One possible role is thermogenesis.