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Bioenergetics and Glycolysis

Bioenergetics and Glycolysis. Getting the E out of C. Overall Chemical Reaction . For all of Cellular Respiration C 6 H 12 O 6 + 6 O 2 ---  6 CO 2 + 6 H 2 O Overall free energy = 687 kcal/mol or 3.8 kcal/g Not really that efficient (Stay tuned for the actual).

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Bioenergetics and Glycolysis

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  1. Bioenergetics and Glycolysis Getting the E out of C

  2. Overall Chemical Reaction • For all of Cellular Respiration C6H12O6 + 6 O2 --- 6 CO2 + 6 H2O Overall free energy = 687 kcal/mol or 3.8 kcal/g Not really that efficient (Stay tuned for the actual)

  3. Energy Transfer follows thermodynamic laws • Gibbs helmholtz ΔG = ΔH – TΔS • Enthalpy • Entropy • Remember ΔSuniverse > 0 is a spontaneous process • Overall if ΔG < 0 the process is spontaneous • ΔG = -RTlnK • Relates ΔG to equilibrium • ΔG are additive • State function • Overall ΔG has to be – for a process to be spontaneous

  4. Le Chatelier’s Principle and ΔG • Remember Le Chatelier and affect on equilibrium • If one reaction has a positive ΔG, but the next reaction, which is in equilibrium has a negative ΔG , the first reaction can be pulled through • Many examples of this in glycolysis

  5. ATP (Adenosine Tri-Phosphate)

  6. Hydrolysis of ATP ATP ------ ADP + Pi + 7.3 kcal

  7. Energy from ATP hydrolysis • 7.3 kcal /mol (30.5 kJ/mol for you SI nuts) • Energy from: • Separation of negative charges • Increased entropy • Phosphate now free…2 things instead of one • Resonance stabilization of phosphate

  8. Other Energy sources • Hydrolysis of thioester • Resonance stabilization of carboxylate • Energy released from group transfer, not simply hydrolysis • Coenzyme A (CoA) is an important thiol that forms thioesters

  9. Coenzyme A

  10. Redox • Review: • Electron transfer reactions • Energy from electron transfer • Electrons typically transferred to a carrier • NAD+ + 2 e- + 2H+- NADH + H+ • FAD + 2 e- + 2H+ - FADH2 • Electrons transferred later for ATP generation

  11. NAD (Nicotinamide Adenine Dinucleotide)

  12. Reduction of NAD+ on Nicotinamide Ring

  13. FAD (Flavin Adenine Dinucleotide)

  14. Reduction of Flavin Ring on FAD

  15. Glycolysis • In Cytosol • Anaerobic • Breakdown of glucose to two pyruvate molecules • Glucose + 2 ADP + 2 Pi + 2 NAD+ - 2 pyruvate + 2 ATP + 2 NADH + 2 H+ • C6H12O6+ 2 ADP + 2 Pi + 2 NAD+ - 2 C3H3O3- + 2 ATP + 2 NADH + 2 H+

  16. Glycolysis

  17. Hexokinase reaction • Irreversible • Kinase (phosphate transfer) • -16.7kJ

  18. Hexose phosphate isomerase reaction • Keto-aldol isomerization • Glucose to fructose • 1.7 kJ

  19. Phosphofructokinase reaction • Same as hexokinase reaction • -14.2kJ • Major point of regulation • Committed step • Stimulated by ADP and AMP • Inhibited by ATP and fatty acids

  20. Aldolase Reaction • Reverse aldol condensation • 23.8kJ • Makes 2 3-Carbon molecules

  21. Triose phosphate isomerase • Keto-enol isomerization (like hexose phosphate isomerase reaction) • 7.5kJ • Net is 2 glyceraldehyde – 3 – phosphate • From now on each reaction times 2

  22. Glyceraldehyde -3-phosphate dehydrogenase • Oxidation coupled to phosphorylation • Makes NADH • 6.3kJ • (remember X 2)

  23. Phosphoglycerate Kinase • Phosphate transfer • Substrate level phosphorylation • Driven by stabilization of carboxylate • -18.5kJ • Pulls previous reactions through

  24. Phosphoglycerate mutase • Moves from 3 - 2 • 2 steps • Makes 2,3 • Removes 3 • 4.4kJ

  25. enolase • Makes unstable enol intermediate • 7.5 kJ

  26. Pyruvate kinase • Last reaction….woohoo • Substrate level phosphorylation • Stabilization of enol - keto • -31.4kJ

  27. Net products from Glycolysis (per glucose) • 2 pyruvate • 2 NADH • 2 ATP • Total energy = -61.3 kJ • Sum of energies

  28. Fates of pyruvate

  29. Fates of Pyruvate • Depend on organism and conditions • Yeast • Anaerobic • Pyruvate decarboxylase • Makes alcohol • Aerobic • Makes acetyl CoA --- energy or fat • Others • Anaerobic • LDH • Makes lactate • Sore muscles • Aerobic • Acetyl Co A --- energy or fat

  30. Glycogen

  31. Glycogenolysis

  32. Glycogen breakdown • Glycogen phosphorylase breaks down alpha 1,4 linkages • Makes glucose-1-phosphate • Enzyme changes to glucose-6-phosphate and enters glycolysis there • Can’t break 1,6 linkages • Debranching enzyme breaks 1,6 (when 4 sugars away from branch) and adds to end • Glycogen phosphorylase takes over and breaks down the rest

  33. Other sugars • Fructose • Comes in at fructose-6-p and immediately phosphorylated • Lipogenic…after branch to glycogen…makes acetyl CoA • Lactose • Glucose and galactose • Galactose • Epimerase turns into glucose-6-P and enters there

  34. gluconeogenesis • Making glucose from pyruvate • In liver • Uses same enzymes as glycolysis except where nonequilibrium reactions • Uses NADPH instead of NADH

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