Bioenergetics

• Bioenergetics


  The metabolic process of converting food into a biologically usable form of energy
• Importance of Bioenergetics


  • Continuously supply energy to perform many complex functions
  • Fuel muscle contractions, build new tissues, preserve lean muscle mass
  • Optimize skeletal structure
  • Repair existing cells
  • Maximize oxygen transport
  • Maintain favorable fluid and electrolyte balance
  • Regulate metabolic processes
• 3 ways to produce energy

  • Creatine Phosphate
  • Anaerobic metabolism
  • Aerobic metabolism
• ATP


  • Ultimate energy source
  • Found within the mitochondria of the body
  • Energy produced from ATP breakdown provides the fuel that activates muscle contractions
  • Stored in limited amounts (approx. 85 grams)
• Creatine Phosphate


  • When ATP loses a phosphate, it then releases energy which results to the combination of adenosine diphosphate (ADP), enzymatically, with another high-energy phosphate from creatine phosphate (CP) to resynthesize ATP
  • The concentration of high-energy CP in the muscle is five times that of ATP
• Creatine Phosphate


  1. Creatine kinase catalyzes the reaction of CP with ADP and inorganic phosphate

  2. This is the fastest and most immediate means of replenishing ATP without using oxygen
• Anaerobic Pathway


  • Also called Lactic Acid pathway
  • The process of anaerobic metabolism supplies ATP for exercises more than 8 seconds
  • This pathway contributes energy during an all-out effort lasting up to 60 to 120 seconds
  • ATP produced through glycolysis is small compared with that available through aerobic pathways
  • Substrate for this reaction is limited to glucose from blood sugar or the glycogen stored in the muscle
  • The coenzyme called nicotinic acid dehydrogenase (NAD) is in limited supply in this pathway therefore, the glycolytic pathway cannot provide constant energy
  • By converting pyruvic acid → lactic acid, NAD is freed to participate in further ATP synthesis
  • When exercise intensifies, body's need for oxygen increases and conversion of lactic acid to fuel hastens therefore, lactic acid accumulates in the blood and muscle, which then lowers the pH to a level that interferes with enzymatic action, and causes fatigue
• Aerobic Pathway


  • A pathway for exercises more than 90 to 120 seconds requiring oxygen
  • Glucose can be broken down far more efficiently for energy, producing 18 to 19 times more ATP
  • This pathway provides ATP by metabolizing fats and proteins
  • Aerobic metabolism is limited by the availability of substrate, a continuous and adequate supply of oxygen, and the availability of coenzymes
  • Cardiovascular fitness – a limiting factor in supplying enough oxygen at the onset of exercise and with increased exercise intensity
• Aerobic Pathway


  1. In the presence of oxygen, pyruvate is converted to acetyl coenzyme A (CoA), which enters the mitochondria. In the mitochondria, acetyl CoA goes through the Krebs cycle, which generates 36 to 38 ATP per molecule of glucose

  2. A large amount of acetyl CoA is provided by beta-oxidation of fatty acids

  3. Proteins may be catabolized into acetyl CoA or Krebs cycle intermediates, or they may be directly oxidized as another source of ATP
• Energy Continuum