Announcements Reading for today on glycolysis: pp 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: , Reading for Friday, Feb. 23 on integration of metabolism: Reading for Monday, Feb. 26 on respiration: 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: 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 respirationO 2 –Complete oxidation of glucose using O 2 as final e- acceptor: ½ O H e -  H 2 O Anaerobic respirationS, H +, Fe 3+ –Complete oxidation of glucose using something other than O 2 as final e - acceptor. Glycolysis is the central catabolic pathway and first part of aerobic respiration:

Oxidation of Glucose C 6 H 12 O O 2  6 CO H 2 O  G o’ = -686 kcal/mol In bomb calorimeter, the large E A of this rxn is overcome by heat of fire. In the cell, a series of reactions with small E A is overcome by body temperature and enzymes. Purpose: convert chemical bond energy of glucose to chemical bond energy in ATP

Glycolysis Problems

Energetics of Glycolysis STEPREACTIONΔG o’ ΔG’ 1GLC + ATP → G6P + ADP + H G6P → F6P F6P + ATP → F1,6BP + ADP + H F1,6BP → DHAP +G3P DHAP → G3P G3P + Pi + NAD+ → 1,3BPG + NADH + H ,3BPG + ADP → 3PG + ATP PG → 2PG PG → PEP + H2O PEP + ADP +H+ → PYR + ATP 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. 1 M Conc., pH=7 cellular Conc., pH=7

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 (CH 3 COCOO - ) Control steps: irreversible reactions 1, 3, and 10