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Metabolic System Unit

Metabolic System Unit. Metabolism, Energy and the Basic Energy Systems. Chapters 2, 3 , and 4. Metabolism. 1. Metabolism energy transfer 1 st Law of Thermodynamics ATP 2. By-products of metabolism heat and biologic work. Energy.

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Metabolic System Unit

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  1. Metabolic System Unit Metabolism, Energy and the Basic Energy Systems Chapters 2, 3, and 4

  2. Metabolism • 1. Metabolism • energy transfer • 1st Law of Thermodynamics • ATP • 2. By-products of metabolism • heat and biologic work

  3. Energy 1. 60% to 70% of the energy in the human body is degraded to heat. • The remainder is used for mechanical work and cellular activities.

  4. Energy 2. The energy we derive from food is stored in a high-energy compound - ATP.

  5. Energy 3. CHO provides about 4.1 kcal of energy per gram, compared to about 9 kcal per gram for fat. • CHO energy is most accessible.

  6. We use CHO in the form of glucose.

  7. CHO gramskcal • Liver glycogen 110 451 • Muscle glycogen 500 2,050 • Glucose in body fluids 15 62___ Total6252,563

  8. We use fat in the form of triglyceride (3 fatty acids and 1 glycerol).

  9. Fat gramskcal • Subcutaneous 7,800 70,980 • Intramuscular 161 1,465 Total7,96172,445

  10. Protein • Protein can also provide energy (4.1 kcal per gram).

  11. We use protein in the form of amino acids.

  12. Energy 5. One kcal equals the amount of heat energy needed to raise 1 kg of water 1 degree C from 14.5 to 15.5 degrees C.

  13. Predominant Energy Pathways • We expend approximately 100 kCal per mile walked or jogged

  14. Definitions • Anaerobic – literally means “without oxygen” • On a local level this might be true • Might be better to think in terms of “hypoxic” which means “too little oxygen”.

  15. Definitions • Aerobic – means “with oxygen” • Both terms relate to energy metabolism or how we transfer and use energy

  16. Practically Speaking • Anaerobic refers to activities that are high in intensity, but short in duration

  17. Practically Speaking • Aerobic refers to activities that are low-to-moderate in intensity and longer in duration.

  18. Difference • The key factor that differentiates the two is how quickly you are able to circulate oxygen to your muscles (cardiorespiratory fitness) versus how quickly you are transferring energy

  19. Difference • If energy demand exceeds oxygen delivery, you are performing anaerobic exercise • If oxygen delivery meets or exceeds energy demand, you are performing aerobic exercise

  20. Energy Transfer • The ATP-CP system relying on the “Phosphogens”. • Anaerobic • The glycolytic (lactic acid) system relying on anaerobic breakdown of CHO. • The oxidative system relying on the aerobic breakdown of • CHO, Fat, and Protein.

  21. Energy Pathways minutes Source: Insel, P., Turner, R.E., and Ross, D. (2006). Discovering Nutrition. Second edition. Sudbury, MA: Jones and Bartlett Publishers.

  22. Anaerobic Metabolism • Anaerobic metabolism refers to the transfer of energy when there is a limited amount of oxygen available. • This occurs when we are first starting to move and also when we are active at high intensity. • At these times, the need for energy is greater than the speed at which the blood can deliver oxygen.

  23. Anaerobic Activities • The ATP-CP and glycolytic systems are major contributors of energy during the early minutes of high-intensity exercise.

  24. Intramuscular ATP • ATPADP + P and release of E • ATPase • 7.6 kcal per mole. • Phosphorylation - process of storing energy by forming ATP from other chemical sources.

  25. Creatine Phosphate • In the ATP-CP system, Pi is separated from CP through the action of creatine kinase. • The Pi can then combine with ADP to reform ATP.

  26. Creatine Phosphate • This system is anaerobic. • Main function is to maintain ATP levels. • Lasts for only 3 - 15 seconds. • Energy yield is 1 mole of ATP per 1 mole of CP.

  27. Glycolysis • The glycolytic system involves the process of glycolysis, through which glucose is broken down to pyruvic acid via glycolytic enzymes. • When conducted without oxygen, the pyruvic acid is converted to lactic acid. • One mole of glucose yields 2 moles of ATP, but 1 mole of glycogen yields 3 moles of ATP.

  28. High-intensity Exercise • The ATP-CP and glycolytic systems are major contributors of energy during the early minutes of high-intensity exercise.

  29. Key Processes • Gluconeogenesis: • The process by which protein or fat is converted into glucose. • Glycogenesis: • The process by which glycogen is synthesized from glucose. • Glycogenolysis: • Breakdown of glycogen for ATP production.

  30. Energy Pathways minutes Source: Insel, P., Turner, R.E., and Ross, D. (2006). Discovering Nutrition. Second edition. Sudbury, MA: Jones and Bartlett Publishers.

  31. Aerobic Activities • The oxidative system involves breakdown of fuels with the aid of oxygen • This system yields much more energy that the ATP-CP (phosphogens) or glycolytic systems

  32. Aerobic Metabolism • Aerobic metabolism refers to the process whereby energy is transferred in the presence of oxygen. • In aerobic metabolism, energy demand does not outpace oxygen delivery.

  33. Aerobic Metabolism • Your heart and circulatory system are able to deliver oxygen in sufficient quantities to meet the body’s needs for energy transfer. • In this circumstance, you initially use carbohydrate as a fuel source and then shift to fat as the primary source.

  34. Aerobic Metabolism • If the intensity remains relatively low, this type of activity can go on indefinitely. • The only limiting factors will be orthopedic stress and low levels of carbohydrate (fat burns in a CHO flame).

  35. Aerobic Metabolism • Oxidation of CHO involves glycolysis, the Kreb’s cycle, and the electron transport system. • The end result is water, CO2 and 36 or 38 ATP per molecule of glucose (38 or 39 per molecule of glycogen).

  36. Aerobic Metabolism • Fat oxidation begins with oxidation of free fatty acids, then follows the same path as CHO oxidation: • the Kreb’s cycle • and the electron transfer system. • The energy yield for fat oxidation is much higher than for CHO oxidation, and it varies with the free fatty acid being oxidized. • Example: You can get up to 463 kCals per fat molecule • (stearic acid)

  37. Electron Transfer System • Final metabolic pathway in the production of ATP • Series of chemical reactions in the mitochondria that transfer electrons from the hydrogen atom carriers NAD and FAD to oxygen • Accounts for the majority of the ATP formation

  38. Ketone Bodies and Ketosis • Ketone Bodies: • Strong acids • Give breath fruity smell • Produced when CHO is not available during fat metabolism • Ketosis • When ketone bodies accumulate, ketosis occurs • Upsets acid-base balance • Most likely caused by anorexia or diabetes

  39. Aerobic Metabolism • Protein oxidation is more complex because protein (amino acids) contains nitrogen, which cannot be oxidized. • Protein contributes relatively little to energy production, so its metabolism is often overlooked.

  40. Protein • Protein can supply up to 5% to 10% of the energy needed to sustain prolonged exercise. • Only the most basic units of protein - amino acids can be used for energy.

  41. Protein • Alternatively, protein can be converted through a series of reactions into fatty acids in a process calledlipogenesis.

  42. Fuel Summary • CHO • Used anaerobically and aerobically • Low amount stored in body • Fats • Used only aerobically • Large amounts stored in body • Can only be used if CHO is available • Protein • Only used in starvation states

  43. Aerobic Metabolism • Your muscles’ oxidative capacity (QO2) depends on its oxidative enzyme levels, its fiber-type composition, and oxygen availability. • The greater the QO2 the more fit the muscle.

  44. Energy Measurement • Direct calorimetry involves using a calorimeter to directly measure heat produced by the body.

  45. Energy Measurement • Indirect calorimetry involves measuring O2 consumption and CO2 release, calculating the RER (or RQ) value (the ratio of these two gas measurements), comparing it to standard values to determine the foods being oxidized, then calculating the energy expended per liter of oxygen consumed.

  46. RQ • RQ = VCO2/VO2

  47. Energy Measurement • For CHO • 6O2 + C6H12O6 = 6CO2 + 6H2O + energy • RQ = 6CO2/6O2 = 1.0

  48. Energy Measurement • The RQ value at rest is usually 0.78 to 0.80.

  49. Respiratory Energy %kcal %kcal Quotient kcal. L-1O2 CHO Fats • 0.71 4.69 0 100.0 • 0.75 4.74 15.6 84.4 • 0.80 4.80 33.4 66.6 • 0.85 4.86 50.7 49.3 • 0.90 4.92 67.5 32.5 • 0.95 4.99 84.0 16 • 1.00 5.05 100.0 0

  50. Myth • Only low intensity exercise causes you to burn fat and lose weight • Corollary – avoid high intensity exercise if you want to lose fat FALSE

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