3.3 Nutrition and Energy systems

• Ultrastructure of a mitochondria is made out of:

  • the cirstae
  • inner matrix
  • outer smooth membrane
• Cell respiration = the controlled release of energy in the form of ATP (Adenosine Triphosphate) from organic compounds in cells
• ATP - a chemical compound which provides energy for muscle contraction
• Explain how adenosine can gain and lose a phosphate molecule:

  • ATP consists of 1 molecule of adenosine and 3 molecules of phosphate
  • energy is released from ATP by breaking the bonds that hold the molecules together

  Process:

  1. bond between the phosphates in broken down by an enzyme
  2. ADP created, energy released
  3. ADP resynthesised into ATP to make it stored energy once more
• Role of ATP in muscle contraction:

  • when muscle fibre is stimulated by the nervous system to contract, the contractile protein molecules use ATP to provide chemical energy
  • ATP provides all energy for muscle contraction
  • in muscles there is sufficient ATP for 2 seconds of muscular activity
  • exercise longer than 2 seconds uses ATP from other energy systems
  • energy systems refers to a set of catabolic reactions occuring within cells whose principal function is generating ATP
• Describe the resynthesis of ATP by the ATP - CP (Creatine Phospahte) system

  • Creatine Phosphate is another high energy chemical compound
  • CP is present within muscles
  • CP cannot be used directly to power muscle contraction
  • chemical energy liberated by the creatine kinase reaction is sufficient to syntehsise ATP
  • CP combined with the 2 seconds of ATP already in muscles, dominates the provision of energy for muscle contraction
  • very quick chemical reaction
  • $Creatine Phosphate +$$ADP +$$H <-> Creatine +$$ATP$
• Phenomena of oxygen deficit and oxygen debt:

  • now known as EPOC - excess post excercise oxygen consumption
  • when oxygen need and oxygen supply do not match
  • during recobery oxygen utilisation continues at a rate greater than needed at rest
  • additional oxygen needed for processes such as restoration of tissue and myoglobin oxygenation
  • to offset the consequences of anaerobic metabolism during recovery
• Production of ATP by the lactic acid system:

  • glycolusis is a metabolic pathway present in the cytoplasm of all cells
  • glycolysis releases some of the energy in glucose as ATP and produces pyruvate
  • when capacity for aerobic metabolism is limited, pyruvate is converted to lactate
  • process occurs very quickly
  • only yields a small amount of ATP : 2 molecules
  • this energy system is optimal to meet high energy demands
• Production of ATP from glucose and fatty acids by the aerobic system:

  1. stored fat broken down into glycerol and fatty acids
  2. fatty ocids undergo beta oxydation
  3. fatty acids broken down into 2 carbon units and catabolised into acetyl coenzyme A enters the Krebbs cycle
  4. electrons released from the Krebbs cycle and Beta oxydation enter the electron transport chain
  5. fatty acids produce more electrons than glucose can produce a greater number of ATP polecules
• ATP - PC system:

  Fuel : Phosphate creatine

  Intensity : maximum intensity

  duration: up to 10 seconds

  Amount of ATP produced: 1

  by products: none
• Lactic acid system:

  Fuel: glucose / glycogen

  Intensity: high intensity

  duration: up to 75 seconds

  Amount of ATP produced: 2-3

  By products: lactic acid
• Aerobic system:

  Fuel: glucose, fatty acids, protein

  Intensity: moderate intensity

  duration: from two minutes to a few hours

  Amount of ATP produced: 34-36

  By products: Carbon dioxide