Energy Metabolism

1. Energy Metabolism

3. 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

4. Energy is stored in food in the form of carbohydrates, Fats and proteins. These basic food components can be broken down in out cells to release the stored energy. • Energy production is both time and intensity related. Running at a very high intensity, as in sprinting, means that an athlete can operate effectively for only a very short period. Running at a low intensity, as in gentle jogging, means that an athlete can sustain activity for a long period.

5. Catabolism and Anabolism • Catabolic reactions breakdown complex organic compounds • providing energy (exergonic) • glycolysis, Krebs cycle and electron transport • Anabolic reactions synthesize complex molecules from small molecules • requiring energy (endergonic) • Exchange of energy requires use of ATP (adenosine triphosphate) molecule.

6. ATP - Adenosine Triphosphate: a complex chemical compound formed with the energy released from food and stored in all cells, particularly muscles. Only from the energy released by the breakdown of this compound can the cells perform work. The breakdown of ATP produces energy and ADP. • CP - Creatine Phosphate: a chemical compound stored in muscle, which when broken down aids in the manufacture of ATP. The combination of ADP and CP produces ATP. • LA - Lactic acid: a fatiguing metabolite of the lactic acid system resulting from the incomplete breakdown of glucose. • O2 means aerobic running in which ATP is manufactured from food mainly sugar and fat. This system produces ATP and is the prime energy source during endurance activities

7. 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

8. ATP IS COMPOSED OF A CARBON NITROGEN BASE CALLED ADENINE, A 5-CARBON SUGAR CALLED RIBOSE AND THEREE PHOSPHATE.

9. Adenosine Triphosphate (ATP)

10. The Alactic Anaerobic Energy System • This energy system is the dominant source of muscle energy for high intensity explosive exercise that lasts for 10 seconds or less. For example, the alactic anaerobic energy system would be the main energy source for a 100 m sprint, or a short set of a weightlifting exercise. • It can provide energy immediately, it does not require any oxygen (that's what "anaerobic" means), and it does not produce any lactic acid (that's what "alactic" means). • It is also referred to as the ATP-PCr energy system or the phosphagen energy system.

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

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

15. Proportion of Aerobic / Anaerobic Production of Energy (ATP)

16. Energy Systems for Selected Sports

17. continued

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

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

20. 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

21. Lactic Anaerobic Energy System • This system is the dominant source of muscle energy for high intensity exercise activities that last up to approximately 90 seconds to 2 minutes. For example, 800 m sprint, 400 m. Essentially, this system is dominant when your alactic anaerobic energy system is depleted but you continue to exercise at an intensity that is too demanding for your aerobic energy system to handle. • this system is also anaerobic and so it does not require any oxygen. However, this system produce lactic acid. It is also referred to as the lactic acid system or the anaerobic glycolytic system.

22. 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

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

24. Selected coenzymes in energy metabolism

25. Anaerobic ATP production ATP can be produced anaerobically through two pathways: ATP-PC system Anaerobic glycolysis

26. 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

27. 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

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

33. 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

34. 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

35. 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

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

37. 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.

38. 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

39. The Krebs cycle occurs within the mitochondria of the muscle fiber • The Krebs cycle is a series of reactions which occurs in the mitochondria and results in the formation of ATP. The pyruvic acid molecules from glycolysis undergo oxidation in the mitochondrion to produce acetyl coenzyme A and then the Krebs cycle begins.

40. Three major events occur during the Krebs cycle. One guanosine triphosphate (GTP) is produced which donates a phosphate group to ADP to form one ATP; three molecules of Nicotinamide adenine dinucleotide (NAD) and one molecule of flavin adenine dinucleotide (FAD) are reduced. Although one molecule of GTP leads to the production of one ATP, the production of the reduced NAD and FAD are far more significant in the cell's energy generating process because they donate their electrons to an electron transport system that generates large amounts ATP.

42. The four steps where NAD is reduced during the aerobic metabolization of carbohydrates • 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

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

44. 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

45. The electron transport system The part of aerobic metabolism where 34 of the 38 ATP are produced

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

47. Most ATP is produced in the electron transport system

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

50. Steps of the citric acid cycle • Step 1. In the first step of the citric acid cycle, acetyl CoA joins with a four-carbon molecule, oxaloacetate, releasing the   CoA, group and forming a six-carbon molecule called citrate. • Step 2. In the second step, citrate is converted into its isomer, isocitrate. This is actually a two-step process, involving first the removal and then the addition of a water molecule, which is why the citric acid cycle is sometimes described as having nine steps—rather than the eight listed here