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Announcements • Reading for today on glycolysis: pp. 221-234 • Homework due today: Problems 8-5, 8-7 – In both problems, use the favorable free energy change of ATP hydrolysis to drive the unfavorable transport of solute up its concentration gradient on a per mole basis. • Reading for Wednesday, Feb. 21 on fermentation and TCA cycle: 236-241, 248-258 • Reading for Friday, Feb. 23 on integration of metabolism: 258-262 • Reading for Monday, Feb. 26 on respiration: 265-271 • Homework due Monday, Feb. 26: Problem 9-5 – Convert all concentrations to M, and your answer will be in M. – Don’t worry about [H+] – use equations as given in problem. – Determine [glucose] at equilibrium (ΔG’ = 0); then a concentration greater than this will favor production of G6P. • Wednesday, Feb. 28 on respiration: 271-283 • Friday: Exam 2 on Days 12-22, 99 points, 33 m/c questions. – Note Exam 3 will be worth 81 points. Outline/Learning Objectives CHO metabolism A.Metabolic reactions and ATP B.Oxidation-reduction reactions C.Glycolysis After reading the text, attending lecture, and reviewing lecture notes, you should be able to: • Describe the roles of ATP/ADP and NAD+/NADH in biological reactions. • Summarize the purpose and place, reactants and products, critical enzymes, and net yield of glycolysis. • Calculate free energy changes associated with glycolysis. • Summarize the products, control steps, etc. of glycolysis. Catabolic and Anabolic Metabolic Pathways Catabolic (degradative) • Glycolysis, fermentation • TCA cycle, electron transport, oxidative phosphorylation • Glycogenolysis • Fatty acid oxidation • Amino acid degradation Anabolic (synthetic) • Gluconeogenesis • Glycogen synthesis • Fatty acid synthesis • Amino acid synthesis ATP is an energy intermediate Donates Phosphate; Hydrolysis is exergonic Accepts Phosphate; Synthesis is endergonic Oxidation and Reduction • Oxidation: gives up e– Dehydrogenation: gives up H+ • Reduction: accepts e– Hydrogenation: accepts H+ • Redox reactions – Usually involve 2 e-, 2 H+ in the cell – Catalyzed by dehydrogenases NAD+ accepts, NADH donates e- NAD+/NADH is an intermediate e- acceptor/donor • Its redox reaction is coupled to another redox reaction in metabolic pathways: NADH + H+ NAD+ + 2e- + 2H+ Acetaldehyde + 2e- + 2H+ ethanol Acetaldehyde + NADH + H+ ethanol + NAD+ This fermentation reaction is catalyzed by alcohol dehydrogenase. Final e- Acceptors • Glycolysis, fermentation (NAD+ ) – No net oxidation of glucose • Aerobic respiration O2 – Complete oxidation of glucose using O2 as final eacceptor: ½ O2 + 2 H+ + 2 e- H2O • Anaerobic respiration S, H+, Fe3+ – Complete oxidation of glucose using something other than O2 as final e- acceptor. • Glycolysis is the central catabolic pathway and first part of aerobic respiration: Oxidation of Glucose C6H12O6 + 6 O2 6 CO2 + 6 H2O Go’ = -686 kcal/mol • In bomb calorimeter, the large EA of this rxn is overcome by heat of fire. • In the cell, a series of reactions with small EA is overcome by body temperature and enzymes. • Purpose: convert chemical bond energy of glucose to chemical bond energy in ATP Glycolysis Problems 2-88 2-89 2-90 2-93 Energetics of Glycolysis 1 M cellular Conc., Conc., pH=7 pH=7 STEP REACTION ΔGo’ ΔG’ 1 GLC + ATP → G6P + ADP + H+ -4.0 -8.0 2 G6P → F6P +0.4 -0.6 3 F6P + ATP → F1,6BP + ADP + H+ -3.4 -5.3 4 F1,6BP → DHAP +G3P +5.7 -0.3 5 DHAP → G3P +1.8 +0.6 6 G3P + Pi + NAD+ → 1,3BPG + NADH + H+ +1.5 -0.4 7 1,3BPG + ADP → 3PG + ATP -4.5 +0.3 8 3PG → 2PG +1.1 +0.2 9 2PG → PEP + H2O +0.4 -0.8 10 PEP + ADP +H+ → PYR + ATP -7.5 -4.0 The table above shows free energy change values in kcal/mol for the concentrations of intermediates in red blood cells. The overall ΔG’ from glucose to pyruvate is about -20 kcal/mol. Glycolysis Summary • Cytoplasmic • Catabolism of: – carbohydrates G6P, F6P – fats: glycerol DHAP – some amino acids pyruvate • • • • Cost = 2 ATP, Gain = 4 ATP, Net Gain = 2 ATP Reduced Coenzymes: 2 NADH + H+ End product: pyruvate (CH3COCOO-) Control steps: irreversible reactions 1, 3, and 10