Chapter 3 Energy Metabolism and Metabolic Adaptations to Training

1. Chapter 3 Energy Metabolism and Metabolic Adaptations to Training

2. Energy metabolism • Energy from the food we eat is stored in the form of ATP • ATP is broken down to liberate the energy used to cause muscle contractions • Anabolism— “to build up”; such as the use of amino acids to make proteins, which contribute to muscle mass • Catabolism— “to break down”; such as breaking down glycogen to glucose molecules

3. Physical educators, coaches, and exercise scientists should have a basic understanding of energy metabolism because • ATP is the source of energy for muscle contraction • Producing enough ATP is essential to performance • Adaptations to exercise training involve energy metabolism • The metabolic demands of training are important in designing training or exercise prescriptions

4. Definitions of anaerobic and aerobic metabolism • Aerobic metabolism is the production of ATP with oxygen. • Anaerobic metabolism is the production of ATP without oxygen.

5. ATP production • ATP can be produced aerobically or anaerobically • Most physical activities involve both aerobic and anaerobic metabolism

6. Approximate percentages of aerobic and anaerobic contributions to ATP production

7. Approximate percentages of aerobic and anaerobic contributions to ATP production (cont.)

8. The three characteristics of enzymes • Speed up or catalyze a reaction • Are not changed by the reaction they cause • Do not change the result of the reaction

9. Lock-and-key method • The enzymes are specific to the reactant to which they bind. • The enzyme must fit precisely with the reactant to catalyze the reaction.

10. What is the respiratory chain? The Krebs cycle and the electron transport system (ETS), where ATP is produced and oxygen is utilized.

11. Summary of aerobic metabolism • Of carbohydrates • Anaerobic glycolysis precedes aerobic phases of ATP production • Of fats (fatty acid oxidation) • Fatty acids are liberated from storage as a part of triglycerides • Long carbon chain fatty acids are metabolized through beta oxidation into two carbon acetyl coenzyme A molecules • These enter the Krebs cycle and go through the ETS for ATP production • Of protein • Amino acids are converted into keto acids by the liver or muscle • Keto acids form substances that produce ATP through the Krebs cycle and ETS

12. Fat, carbohydrate, and protein can be used to produce ATP aerobically

13. Factors that affect the turnover rate of an enzyme • Temperature and pH of the cellular environment • Concentration and activity of reactants and enzymes • Allosteric inhibition • Availability and concentrations of cofactors and coenzymes

14. Selected coenzymes in energy metabolism

15. Anaerobic ATP production ATP can be produced anaerobically through two pathways: ATP-PC system Anaerobic glycolysis Visit Biological Energy Conversion, Review of Anaerobic Metabolism atwww.life.uiuc.edu/crofts/bioph354/lect2.html

16. Myosin ATPase Creatine Kinase (CK) Adenylate Kinase (AK) The three primary enzymatic reactions that occur in the ATP-PC system • ATP ADP + inorganic phosphate (Pi) + energy • PC + ADP ATP + C • 2ADP ATP + AMP

17. Anaerobic glycolysis • The primary system for ATP production for activities that last from approximately 20–30 seconds to two to three minutes • The breakdown of glucose to lactate without the use of oxygen

18. Anaerobic glycolysis involves the breakdown of glucose to lactate.

19. The reactants, enzymes, and products for the two steps in glycolysis where ATP is produced • Step 1 • Reactant: 1, 3-bisphosphoglycerate • Enzyme: phosphoglycerate kinase (PGK) • Product: 3-phosphoglycerate • Step 2 • Reactant: phosphoenolpyruvate • Enzyme: pyruvate kinase (PK) • Product: pyruvate

20. The reactants, enzymes, and products for the two steps in glycolysis where ATP is used • Step 1 • Reactant: blood glucose • Enzyme: hexokinase (HK) • Product: glucose-6-phosphate • Step 2 • Reactant: fructose-6-phosphate • Enzyme: phosphofructokinase (PFK) • Product: fructose-1, 6-bisphosphate

21. The reactant, enzyme, and product for the step in glycolysis where NAD is reduced • Reactant: glyceraldehyde 3-phosphate • Enzyme: glyceraldehyde 3-phosphate dehydrogenase • Product: 1,3-bisphosphoglycerate

22. The reactant, enzyme, and product for the step in glycolysis where NAD is oxidized • Reactant: pyruvate • Enzyme: lactate dehydrogenase • Product: Lactate

23. The role of Phosphofructokinase (PFK) • It is the rate-limiting enzyme in glycolysis • It is the weak link—the rate of conversion of the reactant to product through enzymatic steps can proceed no faster than the rate-limiting enzyme will allow.

24. Aerobic metabolism of carbohydrates • In the presence of sufficient oxygen, pyruvate from glycolysis enters muscle fiber mitochondria • There, ATP is produced in the Krebs cycle and ETS • Produces 38 molecules of ATP per molecule of glucose

25. The Krebs cycle occurs within the mitochondria of the muscle fiber

26. Step 1 Reactant: pyruvate Enzyme: pyruvate dehydrogenase complex Product: acetyl coenzyme A Step 2 Reactant: isocitrate Enzyme: isocitrate dehydrogenase Product: alpha-ketoglutarate Step 3 Reactant: alpha-ketoglutarate Enzyme: alpha-ketoglutarate Product: succinyl coenzyme A Step 4 Reactant: malate Enzyme: malate dehydrogenase Product: oxaloacetate The four steps where NAD is reduced during the aerobic metabolization of carbohydrates

27. The reactant, enzyme, and product for the step in the Kreb’s cycle where FAD is reduced • Reactant: succinate • Enzyme: succinate dehydrogenese • Product: fumarate

28. The reactant, enzyme, and product in the Kreb’s Cycle where ATP is produced • Reactant: succinyl coenzyme A • Enzyme: succinyl coenzyme A synthetase • Product: succinate

29. The electron transport system The part of aerobic metabolism where 34 of the 38 ATP are produced Visit Electron Transport System at http://faculty.nl.edu/jste/electron_transport_system.htm

30. Most ATP is produced in the electron transport system

31. Anaerobic breakdown of glucose results in the net production of only 2 ATP, while aerobic metabolism nets 38 ATP

32. The net chemical reaction of the aerobic metabolism of glucose C6H12O6 + 6O2 + 38ADP + 38P  6CO2 + 6H20 + 38ATP

33. Comparison of the power and capacity of the various energy production systems • The ATP-PC system has low capacity because there is a limited store of phosphagens available. • Carbohydrate oxidation is limited by glycogen depletion. • Fatty acid metabolism has the greatest capacity because, under normal conditions, each person has an inexhaustible supply of energy-rich fats.

34. There is an inverse relationship between the power and capacity of energy production systems

35. The main metabolic adaptations that result from endurance training • myoglobin • mitochondrial size and number • mitochondrial enzymes • lactate production and the role of the Glucose-Alanine-Glucose Cycle • glycolytic enzymes • fatty acid use

36. Effects of sprint training on anaerobic metabolism • enzymes • phosphocreatine stores in the muscle

37. Metabolic effects of resistance training • enzymes • phosphocreatine and ATP stores in the muscle