Metabolism – Intro to Metabolism

1. Metabolism – Intro to Metabolism CH339K

2. Going back to the early lectures

4. Why the big DGo’ for Hydrolyzing Phosphoanhydrides? • Electrostatic repulsion betwixt negative charges • Resonance stabilization of products • pH effects

5. pH Effects – DGo vs. DGo’ (DG in kcal/mol) WOW!

6. Cellular DGs are not DGo’ s DGo’ for hydrolysis of ATP is about -31 kJ/mol Cellular conditions are not standard, however: In a human erythrocyte, [ATP]≈2.25 mM, [ADP] ≈0.25 mM, [PO4] ≈1.65 mM

7. Unfavorable Reactions can be Subsidized with Favorable Ones

9. Activation with ATP - luciferin Excited state of oxyluciferin forms and decays

10. For those who prefer more detail Excerpted from Baldwin, T. (1996) Structure4: 223 – 228,

11. Just because it’s cool… Tobacco seedling w/ cloned luciferase Southeast Asian firefly tree

12. Just because it’s cool… Firefly squid (Watasenia scintillans) of Toyama Bay, Japan New Zealand glowworm (Arachnocampa) cave

13. Hydrolysis of Thioesters can also provide a lot of free energy

14. Acetyl Coenzyme A

15. Sample DGo’Hydrolysis

16. “Phosphate Transfer Potential” is a fancy-schmancy term for –DGo’

17. Electrochemistry in review 1.10 V One beaker w/ ZnSO4 and a Zn electrode One beaker w/ CuSO4 and a Cu electrode Zinc gets oxidized and the electrode slowly vanishes Copper gets reduced and the electrode gets fatter

18. Standard Hydrogen Electrode

19. Redox Table • Higher the SRP, the better the oxidant • Lower the SRP, the better the reductant • Any substance can oxidize any substance below it in the table. • The number of reactants involved doesn’t change the reduction potential • i.e. if a reaction involves 2 NAD+, the SRP is still -0.32 V

20. Electrochemistry in review 1.10 V Zinc gets oxidized Copper gets reduced What determines who gets oxidized?

21. DEo and Keq For an actual half reaction aA + ne-⇌aA- For an actual redox reaction: A+n + ne- ⇌ A B ⇌ B+n + ne- A+n + B ⇌ A + B+n and (Analagous to the relation between DG and DGo’)

22. DEo and Keq (cont.) Atequilibrium, the two are equal: Combining: Or Or Or (rearranging) Dr. Ready gets to the Point!

23. DEo and DGo So: But we already know: Therefore: Another Point!

24. NAD+ Reduction(Nicotinamide Adenine Dinucleotide) NAD+ is a common redox cofactor in biochemistry

25. Coenzyme Q Coenzyme Q is another electron carrier in the cell

26. An Example: What is DGo’ for the Oxidation of NADH by Ubiquinone?

27. Cigarettes ≠ Vitamins

28. “Organic” ≠ “Healthy” Vomiting and nausea, diarrhea, Headaches, Difficulty breathing, Pallor, Sweating, Palpitations, Lisps, Stomach pains/cramps, Seizures, Weakness, Drooling, and - of course - Death

29. Flavins

30. Metabolism • Energy (ATP) • Parts (amino acids, etc.) • Reducing Power (NADH, NADPH) Catabolism (Oxidation) Anabolism (Reduction)

31. Fates of Glucose

32. Catabolism of Glucose C6H12O6 + 6O2 → 6CO2 + 6H2O DGo’ = -2870 kJ/mol It takes 31 kJ/mol to make an ATP. Enough energy is available for making ~90 (theoretically)

33. An aside on diets Glucose (a carb), mol. wt. = 180 g/mol -2870 kJ/mol = -686 kcal/mol -686 kcal/mol / 180 g/mol = 3.8 kcal/g Palmitic Acid (a fatty acid) mol. wt. = 256 g/mol -9959 kJ/mol = -2380 kcal/mol -2380 kcal/mol / 256 g/mol = 9.3 kcal/g Alanine (an amino acid) mol. wt. = 88 g/mol -1297 kJ/mol = -310 kcal/mol -310 kcal/mol / 88 g/mol = 3.5 kcal/g

34. An aside on diets (cont.) From Nutristrategy.com: Fat: 1 gram = 9 calories Protein: 1 gram = 4 calories Carbohydrates: 1 gram = 4 calories The diet values come from the DGo’ for oxidizing the various biomolecules.

35. Catabolism of Glucose

36. Interconversion of C6 Sugars Glycogen Glucose-1-Phosphate -7.3 kJ/mol Glucose Glucose-6-Phosphate Amino Sugars -0.4 kJ/mol Nucleotides Fatty Acids Fructose-6-Phosphate Catabolism

37. STOP HERE FOR INTRO LECTURE

38. Glucose Catabolism Part 1:Glycolysis • Aka Embden-Meyerhof pathway • Worked out in the 1930’s • Partially oxidizes glucose • Uses no O2 • Takes place in cytoplasm

39. Interconversion of C6 Sugars (Again) Glycogen Glucose-1-Phosphate -7.3 kJ/mol Phosphoglucomutase Glucose Glucose-6-Phosphate Amino Sugars -0.4 kJ/mol Phosphohexose isomerase Nucleotides Fatty Acids Fructose-6-Phosphate Catabolism

40. Don’t Eat the Toothpaste! • Phosphoglucomutase contains a PO4-2 group attached to residue D8. • Fluoride has a number of toxic effects • One of them is the removal of the phosphate from phosphoglucomutase • No phosphate = no activity • No activity = can’t utilize glycogen

43. Glycolysis - Energetics

44. Phosphohexose Isomerase

45. Aldolase

46. Aldolase Reaction • The standard free energy , DGo,for the aldolase reaction is very unfavorable (~ +25 kJ/mol) • Under cellular conditions, the real free energy, DG, is favorable (~ -6 kJ/mol) • [G-3P] is maintained well below the equilibrium level by being processed through the glycolytic pathway

47. Triose Phosphate Isomerase

48. Gyceraldehyde-3-P Dehydrogenase

49. Phosphoglyceromutase H8 in human erythrocyte PGM

50. Overall Reaction The overall reaction of glycolysis is: Glucose + 2 NAD+ + 2 ADP + 2 Pi 2 pyruvate + 2 NADH + 2 ATP + 2 H2O + 4 H+ • There is a net gain of 2 ATP per glucose molecule • As glucose is oxidized, two NAD+ are reduced to 2 NADH