BIOENERGETICS

1. BIOENERGETICS MALIK ALQUB MD. PHD.

2. 1st Law of Thermodynamics • The First Law of Thermodynamics states that energy cannot be created or destroyed but only changes forms. • In the introductory activity chemical energy in our bodies was changed to mechanical energy in our arms. • Friction caused some of this mechanical energy to be changed to noticeable heat energy in our hands.

3. 2nd Law of Thermodynamics • The Second Law of Thermodynamics states that at every energy transfer some portion of the available energy is degraded to heat which moves to cooler objects.

4. The human body Air-conditioningsystems Airplanes Car radiators Power plants Refrigeration systems 1-1 Applications of Thermodynamics

5. High energy vs. Lowenergy state Transition state High energy Lowenergy

6. High energy vs. Lowenergy state Transition state Intial state ∆G is negative Final state

7. ∆G; free energy change • ∆G= final energy state – intial energy state • or • ∆G= low energy state – high energy state • then • Change in free energyisnegative (∆G is negative) • Thatsmean • There is a net loss of energy (exerogenic)

8. High energy vs. Lowenergy state Transition state Intial state ∆G is positive Final state

9. ∆G; free energy change • ∆G= final energy state – intial energy state • or • ∆G= high energy state – low energy state • then • Change in free energyis positive (∆G is positive) • Thatsmean • There is a net gain of energy (endergonic)

10. ∆G; free energy change • Exergonic reactions • Chemical processes that release energy to its surroundings • Downhill processes • Endergonic reactions • Chemical processes that store or absorb energy • Uphill processes

11. CoupledReactions

12. Coupled Reactions

13. Factors Affecting Bioenergetics • Enzymes • Reaction rates • Enzyme mode of action • Coenzymes

14. Enzymes • Are highly specific protein catalysts • Accelerate the forward and reverse reactions • Are neither consumed nor changed in the reaction • pH and temperature dramatically affect enzyme activity

15. Reaction Rates • The rate of exergonic and endergonic reactions depends on: • Substrate availability • Enzyme availability • Metabolic state of the cell • Cellular conditions (temperature, pH) • Energy charge is maintained.

16. Coenzymes • Complex nonprotein organic substances facilitate enzyme action by binding the substrate with its specific enzyme • Coenzymes are smaller molecules than enzymes • Many vitamins serve as coenzymes, e.g. riboflavin and niacin

17. Phosphate-Bond Energy

18. ATP: The Energy Currency • ATP is ideally situated in the middle of the list of compounds, as it yields less energy than some, but it also requires less energy to be reconstituted. • ATP + H2O ↔ ADP + Pi + free energy + heat • ATP hydrolysis yields 7.3 kcal of free energy.

19. Structure of Adenosine Triphosphate (ATP)

20. Synthesis of ATP

21. Creatine Phosphate • Energy rich phosphate compound closely related to ATP. • Contains energy rich phosphoanhydride bond. Insert Figure 3.7

22. Released energy is coupled with energy requirement for re-synthesis of ATP. • For every mole of PCr broken down, 1 mole of ATP synthesized. • The coupled reaction is:

23. Cellular Oxidation • Human energy dynamics involve transferring energy by chemical bonds. • Energy for phosphorylation comes from oxidation of carbohydrate, lipid, and protein macronutrients.

24. Cellular Oxidation Oxidation reaction: an element loses electrons (e-); a compound loses electrons, often accompanied by hydrogen ions (H+), or it gains oxygen. Reduction reaction: an element gains electrons (e-); a compound gains electrons, or it loses oxygen.

25. Cellular Oxidation • Oxidation-reduction reactions are coupled. Every oxidation coincides with a reduction. • OILRIG: Oxidation Involves Loss Reduction Involves Gain • LEO the lion says GER: Lose Electrons Oxidation Gain Electrons Reduction

26. Cellular Oxidation Oxidation-reduction reactions are coupled. Every reduction coincides with a oxidation (redox). Cellular oxidation-reduction constitutes mechanism for energy metabolism. Carbohydrate, fat, and protein provide hydrogen atoms for this process.

27. Cellular Oxidation • Hydrogens released from food molecules picked up by coenzyme NAD+ & sometimes FAD in cytosol. • Substrate oxidizes & loses hydrogens (electrons), NAD+ gains a hydrogen & 2 electrons and reduces to NADH, the other H+ in fluid

28. Energy Release from Food

29. Electron Transport Chain • The NADH and FADH2, formed during glycolysis, β-oxidation and the TCA cycle, give up their electrons to reduce molecular O2 to H2O. • Electron transfer occurs through a series of protein electron carriers, the final acceptor being O2; the pathway is called as the electron transport chain. • ETC takes place in inner mitochondrial membrane where all of the electron carriers are present. • The function of ETC is to facilitate the controlled release of free energy that

30. Oxidative Phosphorylation • Energy is released when electrons are transported from higher energy NADH/FADH2 to lower energy O2 . • This energy is used to phsophorylate ADP. • This coupling of ATP synthesis to NADH/FADH2 oxidation is called oxidative phosphorylation. • Oxidative phosphorylation is responsible for 90 % of total ATP synthesis in the cell.