ATP-PC system

• ATP = adenosine triphosphate

  • stored in the muscle cell
  • made up of one adenosine and three phosphates
  • when broken down energy provided for cellular processes such as digestion, nerve transmission and muscular contractions.
• ATP breakdown:

  • to extract energy, enzyme ATPase is released, which stimulates the final high energy bond to be broken
  • exothermic reaction - releases energy for muscular contraction and leaves adenosine diphosphate (ADP) and one phosphate (P).
• ATP breakdown:

  ATP → (ATPase) ADP + P + energy

  Adenosine triphosphate → adenosine diphosphate + phosphate + energy
• ATP resynthesis:

  • The store of ATP in the muscle cell is exhausted quickly lasting 2-3 seconds
  • In order to continue exercising ATP must continue to resynthesise
  • endothermic reaction - energy from surrounding area is absorbed to rebuild the high energy bond between ADP and phosphate
  • energy provided by one of the three energy systems which break down food fuels
• energy systems:

  • ATP-PC system
  • Glycolytic system
  • Aerobic system
• ATP-PC system:

  • very high intensity exercise
  • after the first 2 seconds of intense activity depletes the original ATP stores
  • ATP levels fall and ADP and phosphate levels rise
  • triggers the release of creatine kinase, an enzyme which catalyses the breakdown of the immediately available fuel phosphocreatine (PC)
• ATP-PC system:

  • Phosphocreatine made up of creatine with high energy phosphate bond and is stored on the site in muscle cells
  • phosphocreatine is broken down anaerobically in the sarcoplasm
  • high energy bond between creatine and phosphate is broken, releasing energy for ATP resynthesis
  • for every one mole of phosphocreatine broken down, one mole of ATP can be resynthesised
• ATP-PC system:

  • forms a coupled reaction whereby the breakdown of phosphocreatine releases a free phosphate and energy which can be used to resynthesise ATP
  • very quickly as both compounds are simple structures, providing energy for very high intensity exercise
  • phosphocreatine stores are small and quickly exhausted after 8 seconds
• PC → (creatine kinase) P + C + energy

  ADP + P + energy → ATP
• type of reaction - anaerobic

  site of reaction - sarcoplasm

  fuel used - phosphocreatine (PC)

  enzyme - creatine kinase

  ATP yield - 1 mole of PC = 1 mole of ATP

  intensity - very high intensity

  duration - 2-10 seconds
• strengths:

  • no delay of oxygen
  • phosphocreatine readily available in muscle cell
  • simple and rapid breakdown of phosphocreatine
  • provides energy for very high intensity exercise
  • no fatiguing by-products and simple compounds aids fast recovery
• weaknesses:

  • low ATP yield
  • small phosphocreatine stores leads to rapid fatigue after 8-10 seconds