1. PART II: Energetics and Enzymes

2. Free energy of formation (G 0 f ) for compounds Energy needed for the formation of a compound Used to calculate ΔG 0 ’ of a reaction If the formation of a compound is exergonic, then Gº f is - If the formation of a compound is endergonic, then Gº f is +

3. Free energy of formation

4. Predicting reactions ΔGº’ of A+B  C+D Gº f [products]- Gº f [reactants] ΔGº’ of the reaction H 2 + ½ O 2  H 2 O ΔGº’= Gº f [H 2 O]- (Gº f [H 2 ] + Gº f ½ O 2 ) (- 237.2) – (0 + ½ 0) = - 237.2 KJ/mol Is this endergonic or exergonic?

5. What is the ΔGº’ of the following reactions? CH 4 + ½ O 2  CH 3 OH H 2 S + 4H 2 0 + 8Fe +3  8Fe +2 + 10H + + SO4 -2 (at pH7)

6. Enzymes associate with other molecules Prosthetic groups –Bound very tightly to enzymes –Example: heme group in cytochromes Coenzymes –Bound loosely to the enzyme –Examples: vitamins

7. PART III Oxidation-Reduction and Energy-Rich Compounds

8. Example H 2 + fumarate 2-  succinate 2- –Oxidation of Hydrogen: (electron donor) –H 2  2 e - + 2 H + –Reduction of fumarate: (electron acceptor) –fumarate 2- + 2 e - + 2 H +  succinate 2- 2 half reactions – are linked 1 reaction = oxidation and electron donor 1 reaction = reduction and electron acceptor

9. Reduction potential, E 0 ' The tendency of a compound to accept or release electrons Vertical tower of reduction potentials The most negative E 0 's on the top – Greatest electron donor potential Those with the most positive E 0 's on the bottom –Greatest electron acceptor Donors can pass electrons to acceptors below them on tower only As electrons are passed from a donor, energy is released  E 0 ‘ =  G 0 '

10. Electron tower

11. Questions? Which compound on the tower has the greatest ability to donate electrons? Which compound on the tower has the greatest ability to accept electrons? Can cytochrome B donate electrons to iron (Fe +3 )? Can ubiquinone accept electrons from iron Fe +3 ?

12. Does anyone know in the electron transport chain, what compound has the greatest ability to accept electrons and what compound has the greatest ability to donate electrons?

13. Reduction potentials ΔEo’= difference in potential –The larger the ΔE o ’ during a redox reaction, the greater the energy released –Or the farther the electrons fall down the tower the more potential energy produced

14. Redox reactions in metabolism NAD + /NADH: catabolic reactions NADP + /NADPH: anabolic reactions NAD + /NADH, E 0 ’ = -0.32 Is NADH a good electron acceptor or electron donor?

15. In metabolism there are different electron carriers NADH FADH 2 NADPH They carry hydride ions = 2 hydrogen + 2 electrons Acetyl CoA – carries an activated sulfhydryl group ATP carries an activated phosphate group

16. Questions Is NAD+ in the oxidized or reduced form? Is FADH 2 in the oxidized or reduced form? If a series of reactions is about to take place, would you say that NADH is going to be oxidized or reduced? What about FAD+? Which of the following compounds would pick up electrons – NAD+, NADH, FAD+ or FADH 2 ?

17. Role of NAD + /NADH in metaobolism NADH is formed during glycolysis NAD+ is regenerated during fermentation or the electron transport chain

18. Carrier molecules involved in different biochemical reactions Carrier moleculeGroup carried ATPphosphoryl NADH and NADPHelectrons (and hydrogen) FADH 2 electrons (and hydrogen) Coenzyme Aacetyl

19. High Energy Bonds