1. Bioenergetics Intro/Chpt 14

2. Catabolism & energy prod’n in cells (Fig. 4, p487) Glycolysis Intermediary metabolism ATP production –Mitochondrial –Chloroplast

3. Fig. 4, p.487

4. Regulatory enzymes Rate limiting Modulators control +/- –Allosteric –Covalently modified –Combination Pathway commitment

5. Metabolic rxns follow trends ~ 50 rxns –Only 5 major types (REMEMBER?) Coupling Redox rxns impt

6. Thermodynamics (again!)  G =  H - T  S –  G - = Exergonic = heat given off –  H - = Energy released w/ bonding rxn –  S + = Increased entropy (incr’d randomness)  G o’ = Std free energy (pH=7, [H 2 O]=55 M, [reactant]=1 M, T=25 o C) = physio cond’s in cell

7. Thermodynamics (again!) For cellular rxn: a A + b B c C + d D at equilib –K’ eq can be written –K’ eq related to  G o’ (Table 14-2) Can predict  G o’ from K eq and vice/versa (Table 14-3)

10. In real life Not all reactants @ 1 M –Go back to  G –  G =  G o’ + RT ln ([C] c [D] d /[A] a [B] b ) –Theoretical max energy for rxn Actual energy available to system < theoretical

11. In real life – cont’d Not all thermodynamically favorable rxns proceed at measurable speeds –Enzyme catalysis impt –  G relationship to k is inverse and exponential (REMEMBER??) –  G stays the same

12. In sequential reactions If common reactants, products:  G o’ values are additive –So thermo’ly unfavorable rxn can be driven by thermo’ly favorable rxn coupled to it Keq values are multiplied –So see large differences in Keq of coupled rxns Commonly coupled to endergonic rxns: –ATP hydrolysis:  G o’ = -30.5 kJ/mole –Coupling hydrol of n ATPs raises Keq by 10 8n

13. ATP hydrolysis adds energy Products of hydrolysis are resonance stabilized (14-1) –Decr’d electrostatic repulsions in ADP –P i O’s can share – charge

14. Fig. 14-1

15. ATP hydrolysis adds energy Mg coordinates w/ ADP (14-2)

16. ATP hydrolysis adds energy P i or AMP often cov’ly couples w/ reactants –  High energy intermediate –Larger  G when cleaved –Glutamate (14-8) –First step in glycolysis activates glucose

17. Fig. 14-8

18. Some notes… ATP may bind non-covalently to protein; hydrolysis provides energy for conform’l change –Ex: Na+/K+ ATPase Other phosphorylated cmpds release energy w/ cleavage of P i (Table 14-6) –Products also often resonance stabilized (14-3, 14-4) –BUT original source of P i is ATP  ADP + P i

20. Fig. 14-3

21. Fig. 14-4

22. Some (more) notes… Thioesters impt –Acetyl CoA example (14-6) –Greater  G for hydrolysis (14-7) Nucleoside triphosphates are source of nucleotides inc’d into DNA, RNA (w/ release of energy) (14-12)

23. Fig. 14-6

24. Fig. 14-7

25. Fig. 14-12

26. Biological Oxidation Reduction Reactions (Redox) Flow of e-’s changes redox state of reactants, products –Reactant that goes from more red’d  more ox’d –e-’s accepted by another molecule, goes from more ox’d  more red’d

27. Redox Rxns – cont’d Battery as example of e- flow  energy –Two linked sol’ns w/ differences in affinities for e- –Coupled through e- carrier –Carrier associated w/ motor, which can give off energy (in the form of work)

28. Redox Rxns – cont’d Cellular analogy –Two sol’ns = two molecules w/ differing affinities for e- –e- carrier = cofactor (molecule) –Motor = ATP synthesis “machine” in mitochondrion which can give off energy (in the form of a chemical with high potential chemical energy)

29. Redox Rxns – cont’d Metabolism of nutrients converts cmpds from more red’d  more ox’d states –By LEO/GER, nutrient loses electrons (e-‘s) –e-‘s released to system BUT are NOT free in cytoplasm –e-‘s transferred to carrier mol’s By LEO/GER, carrier mol’s now red’d

30. Biological Oxidation Reduction Reactions (Redox) – cont’d Red’d carrier mol’s bring e-‘s to mitoch –Electron transport system –Coupled to oxidative phosph’n –  ATP prod’d

31. Redox Rxn’s (cont’d) Rxns of e- flow (reductant [or e- donor]  oxidant [or e- acceptor]) can be additive Imptc – free energy of system changes w/ change in red’n potential of reactants/products in rxn  E = diff in red’n potentials of reductant, oxidant –Related to free energy of system (  G) (eq’n 14-6) –Use to calc  G’s for biol. oxn’s

32. Redox Rxn’s (cont’d) e- flow from lower red’n potential  higher red’n potential (Table 14-7) E o’ additive if coupled rxns have common intermed’s –Use to calc  G’s for biol. oxn’s

33. Redox Rxn’s (cont’d) Cells’ rxns (incl redox) involve organic cmpds Consider “ownership” of e- by C in a cmpd (14-13) Ox’n C-cont’ng cmpds often w/ bonding O to C, displacing H –More red’d cmpds – more H’s, fewer O’s –More ox’d compds – more O’s, fewer H’s

34. Fig. 14-13

35. Redox Rxn’s (cont’d) Oxidation may occur in 4 ways –Electrons transfer directly –As H+ + e- –As combination w/ O 2 –As :H- (hydride ion) Common mechanism w/ carriers “Reducing equivalents”

36. Nicotinamides -- NAD, NADP When ox’d: NAD+, when red’d: NADH One C on nicotinamide ring accepts e- as :H- Hydride donor also releases one H+ to system –Overall: NAD+ + 2e- + 2H+  NADH + H+

37. Fig. 14-15a

38. NAD, NADP – cont’d NADP+ preferred by some enz’s, species –[NAD+/NADH] >> [NADP+/NADPH] [NAD+] usually > [NADH] –Commonly donates or accepts hydride? [NADP+] usually < [NADPH] Enz’s = oxidoreductases or dehdrogenases –> 200 (Table 14-8) Loosely assoc’d w/ deHases –Move between enzymes –Recycled by cell

40. Flavin Nucleotides – FMN, FAD Der’d from riboflavin Isoalloxazine ring accepts 1 or 2 e- –Semiquinone (partly red’d) –Quinone (fully red’d) Often bound more tightly to enz’s –“Prosthetic grps” Varied enz’s associate w/ flavins –Table 14-9

41. Fig. 14-16