Energy Supply During Muscle Contraction

• Muscle contraction requires energy which is supplied by the hydrolysis if ATP. The energy is used to:

  • move the myosin heads into a cocked position.
  • active transport of Ca 2+ into sarcoplasmic reticulum
• In active muscle ATP is regenerated by:

  • Aerobic respiration of pyruvate
  • Anaerobic respiration. NAD runs out in the absence of oxygen. Pyruvate accepts H+ from NADH to form lactate so the NAD can accept another H atom in glycolysis, producing 2ATP.
• In active muscle ATP is regenerated by:

  Phosphorylating ADP using a Pi from phosphocreatine.

  Phosphocreatine is stored in the myofibrils and acts as reverse of phosphate ions which can combine immediately with ADP to form ATP. The phosphocreatine store is replenished when the muscle relaxes.
• Slow-twitch Fibres

  Common in posture/core muscles.
• Slow-twitch Fibres

  Slow to contract- produce ATP slower as they're adapted for aerobic respiration due to:

  • larger amount of myoglobin (pigment that stores O2)
  • rich blood supply
  • many mitochondria
  • less power - less myosin
  • perform for exercise for longer
• Fast-twitch Fibres

  Common in leg muscles.
• Fast-twitch Fibres.

  • Contract rapidly - produces ATP quickly due to high levels of anaerobic enzymes, stores of phosphocreatine.
  • Powerful contractions - due to more myosin filaments.
  • Used in short duration exercise- due to lactic acid build up.