Three Energy Systems

2. Three Energy Systems • ATP regenerated by PCr • Oxidative Phosphorylation • Glycolysis

3. ATP (adenosine triphosphate) • remove one phosphate bond from ATP, have ADP adenosine diphosphate • loss of second - AMP, adenosine monophosphate

4. ATP + H2O ↔ ADP + P via ATPase

5. ATP is located throughout the cytoplasm and nucleoplasm of all cells

6. Creatine Phosphate (CP) (or Phosphocreatine PCr ) • high energy phosphate, a donor of P to ADP • PCr + ADP + H → Cr + ATP via CPK (creatine phosphokinase or creatine kinase )

7. Rapid resynthesis of ATP, nonaerobic

8. 3-4 X more PCr than ATP • ATP: 2-6 mmol/kg • PCr: 18-20 mmol/kg • PCr is high energy phosphate reservoir

9. Intramuscular Stores can only last for about 10 sec. during maximal work

10. When both ATP and PCr stores are depleted : • Two ADP can form one ATP via adenylate kinate (myokinase in muscle)

11. Phosphorylation • transfer of energy in the form of phosphate bonds • energy for this is from cellular oxidation of substrates

12. Oxidative Phosphorylation • formation of ATP from ADP and Pi in association with the transfer of electrons from fuel molecules to coenzymes to oxygen (aka cellular oxidation) • occurs in the mitochondria

13. Cellular Oxidation • transfer of electrons for hydrogen to oxygen • result from metabolism of substrates CHO,fat, protein • during metabolism, H ions are removed from these substrates and carried by carrier molecules to the mitochondria, where the electron transport system resides

14. Electron Transport Chain • NAD+ (nicotinamide adenine dinucleotid) and FAD (flavin adenine dinucleotide) are the electron (hydrogens) acceptors to be passed down the ETC “bucket brigade” to coenzyme Q, to the cytochromes

15. energy potential is decreased as the hydrogen ions are removed (to bind with oxygen to make water) • only the last cytochrome, aa3, can release the hydrogen directly to the oxygen

16. Oxidative Phosphorylation and Electron Transport are separate, but linked

17. P/O ratio • reflects the coupling of ATP production to the electron transport • NADH P/O ratio = 3, FADH P/O ratio = 2

18. Continuous Resynthesis of ATP • donor electrons (NADH, FADH), reducing agent • oxygen as electron acceptor • enzymes for pathway

19. CHO: primary function: fuel • only macronutrient that can generate ATP anaerobically • during light to moderate intensity: 1/2 the energy requirement • need CHO to feed “flame” of fat catabolism (CHO flame)

20. human skeletal muscle: ~80-100 mM of glycogen/kg of wet wt (15-18 g of glycogen) • 70 kg male: ~400 g of muscle glycogen in whole muscle pool • 5-6 g of glucose available in blood • liver: ~50-90 g of available glycogen

21. Release of glucose • blood glucose concentrations • hormonal interactions: insulin, glucagon, norepinephrine, epinephrine (catacholamines)

22. Review of Terms: • Glycolysis: catabolism of glucose • Glycogenolysis: catabolism of glycogen • Gluconeogenesis: form new glucose • Glucogenesis: form new glycogen • Glucagon: hormone

23. Glygolysis/Embden-Myerhoff pathway • occurs in the cytosol • net 2 ATP • Glucose must be transported into the cell • 4 glucose transporters: • Glut 1 Glut 3 • Glut 2 Glut 4 • Glut 4 is in skeletal muscle

24. Fate of glucose and ratio of lactate to pyruvate depends on: • enzyme kinetics • mitochondrial capacity of cell • hormonal control • oxygen availability • required rate of energy production and energy needs

25. Gycolysis regulation • Hexokinase • Phosphofructokinase • Pyruvate Kinase (liver, not sk. mu.)

26. NADH must be shuttled to mitochondria via malate-aspartate shuttle

27. FADH is shuttled via glycerol-phosphate shuttle

28. Glucose Paradox • liver prefers to make GLYCOGEN from lactate rather than from glucose • glucose is available to the rest of the body (brain, cns, skeletal muscle)

29. LDH is in competition with mitochondria for pyruvate

30. LDH: two types • heart • muscle: high affinity for pyruvate, higher biological activity than H type • 5 isozymes