Nutrient Role in Bioenergetics

1. Nutrient Role in Bioenergetics Chapter 4

2. Bioenergetics • Bioenergetics refers to the flow of energy within a living system. • Energy is the capacity to do work. • Aerobic reactions require oxygen. • Anaerobic reactions do not require oxygen.

3. Bioenergetics • First law – Energy is neither created nor destroyed, but instead, transforms from one state to another without being used up.

4. Bioenergetics • There are six forms of interchangeable energy states: • Chemical • Light • Electric • Mechanical • Heat • Nuclear

5. Bioenergetics The process of photosynthesis is a chemical reaction. • Chlorophyll absorbs radiant energy: • To synthesize glucose from carbon dioxide and water • To release oxygen. • Solar energy and photosynthesis provide power to the animal world through food and oxygen.

6. Bioenergetics

7. Photosynthesis • What is the equation for the chemical reaction of photosynthesis?

8. Bioenergetics • Respiration is the reverse of photosynthesis. • C6H12O6 + O2→ 6CO2 + 6H2O

9. Cellular Respiration • Organism transforms the chemical energy into a form it can use. • Cellular Respiration-Step by step process • Glucose • Lipids • Amino acids • Heat

10. Bioenergetics • Takes one of three forms: • Mechanical work of muscle contraction • Chemical work for synthesizing cellular molecules • Transport work that concentrates diverse substances in body fluids

11. Bioenergetics • Potential energy • Energy associated with a substance’s structure or position. • Kinetic energy • Energy of motion. • Potential energy and kinetic energy • The total energy of any system.

12. Bioenergetics

13. Adenosine Triphosphate

14. Bioenergetics • Cellular Oxidation–Reduction Reactions • Constitute the mechanism for energy metabolism • Redox reactions power the transfer process of energy

15. Bioenergetics • Oxidation–reduction reactions couple: • Oxidation = a substance loses electrons • Transfer oxygen, hydrogen, or electrons • Reduction = a substance gains electrons • Atoms gain an electron-reducing valence

16. Coupled Reactions

17. Coupled Reactions • Reduction Reaction • 2C3H4O3 + 2H → 2C3H6O3 • LDH • Pyruvate (gains 2 e-) → Lactate

18. Coupled Reactions • Oxidation Reaction • 2C3H6O3 - 2H → 2C3H4O3 • LDH • Lactate (loses 2 e-) Pyruvate

19. Bioenergetics • ATP – energy currency • Potential energy extracted from food • ATP • Chemical energy extracted for biologic work • Cells • Muscle contraction

20. Phosphate Bond • Stored or potential energy • High energy bonds • ATP – hydrolysis • ATP + H2O → ADP + P – 7.3 kCal/mole • ATPase

22. Bioenergetics

23. Bioenergetics • Phosphocreatine (PC) is also a high-energy phosphate compound. • ATP-PC (phosphagens) • Releases energy when bonds between creatine and phosphate are broken. • Sustains all out exercise ~ 5-8 s • Resynthesis of ATP used – reservoir • Stored in muscle - anaerobic

24. Bioenergetics • Cells store 4-6 times more PCr than ATP • Muscle • Provide a reservoir of high-energy phosphate bonds • ATP + H2O  ADP + Pi • ATPase • ADP + C~P  ATP + C • Creatine kinase

26. Bioenergetics • Phosphorylation • Refers to energy transfer through phosphate bonds • Oxidative phosphorylation • Synthesizes ATP by transfer of electrons • NADH and FADH2

27. Cellular Oxidation-Reduction Reactions • Mechanism for energy metabolism • Involves transfer of hydrogen atoms • Loss of hydrogen: oxidation • Gain of hydrogen: reduction

28. Cellular Oxidation • Mitochondria • NAD and FAD → NADH and FADH2 • Cytochromes – Electron Transport Chain (ETC) • Transfer of electrons (H+) • Energy conserved – high energy phosphate bonds • Figure 4.11

29. Bioenergetics • Sources for ATP formation include: • Glucose derived from liver glycogen • Glycogenolysis • Triacylglycerol and glycogen stored in muscle • Free fatty acids - circulating • Triacylglycerol in liver, adipocytes • Lipoprotein complexes - circulating • Amino acids • Intramuscular and liver-derived carbon skeletons

30. Bioenergetics