Energy Systems OCR PE


  • Created by: Jade
  • Created on: 27-01-11 10:13

Energy Basics

  • sun gives off light energy
  • plants convert light energy into stored chemical energy
  • humans consume this energy by eating plants
  • energy is then stored in humans as carbohydrates, fats or proteins
  • chemical energy stored as a high energy compound of adenosine triphosphate (ATP)
  • energy stored within this compound ATP is called potential energy
  • Potential energy is readily available as energy for muscles to contract
  • The energy made to make muscles move is called kinetic energy
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Key Definitions

Adenosine Triphosphate (ATP) - chemical energy stored as a high energy compound in the body. it is the only immediate usable source of energy

potential energy - 'stored' energy which is ready to be used when required

Kinetic energy - energy in the form of muscle contraction/joint movement

'energy is the ability to perform work or put mass into motion and usually measure in joules'

'work is done when a force is applied to a body to move it over a certain distance'

work (Joules) = force(N) x distance moved(M)

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one molecule of adenosine and three phosphates

importance? - only usable form of energy in the body - food has to be converted to ATP first

Energy released - Breaking the high energy bond

ATPase - enzyme used to break bonds (exothermic)

ATP + ATPase -->  ADP(Adenosine diphospate) + energy

ATP ---> ADP + P + energy

exothermic reaction, energy converted into kinetic or heat energy

ADP + P + energy - - - > ATP      (endothermic reaction)

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Re-synthesise ATP

3 ways in which it can be re synthesised...

1) phosphocreatine system (ATP-PC) = 0-10 seconds - anaerobic

2) Lactic acid system = 10 secs - 3 minutes - anaerobic

3) the aerobic process = excess 3 mins - must use oxygen

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Phosphocreatine System

Uses high energy compound phosphocreatine to join ADP and P

PC = P + C + energy (EXO)              

Energy +ADP + P = ATP (endo)   Known as a coupled reaction

reactions take place on the sarcoplasm of the muscle cell and does not need oxygen

Creatinekinase is the enzyme that breaks down the phosphocreatine

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advantages and disadvantages of ATP-PC


  • does not require oxygen
  • PC store already in muscle cells as an energy source
  • simple compound to break down so quick energy source
  • automatically stimulated by a decrease in ATP
  • provides energy for explosive, high intensity movement
  • no fatigue due to by products
  • PC can itself be quickly re synthesise


  • small amount of PC stored
  • 1 PC = 1 ATP
  • only lasts between 8-10 seconds
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Lactic Acid System

Occurs in the sarcoplasm and doesn't require oxygen. Glucose and Gylcogen stored in the liver

the system starts when there's a reduction in PC or an increase in calcium

it stops due to a reduction in PH or an increase in PC

Lactic acid system is effected by onset of Blood Lactate Accumulation (OBLA)

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Lactic Acid system Process

  • Glycogen is found stored in the liver and broken down by glycogen phosphorylase
  • ATP is added to the system
  • broken down glycogen produces glucose - 6 - phosphate
  • Phosphofructokinase (PFK) is added to break down glucose - 6 - phosphate
  • pyruvic acid is formed which also prodcues 2 ATP
  • this is broken down by lactate dehydrogenase to form lactic acid
  • the change in PH occurs from the H+ ions joining to pyruvic acid and lactic acid
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Advantages and Disadvantages of Lactic Acid


  • 2 ATP produced
  • requires fewer reactions
  • can occur in the absense of oxygen
  • glycogen readily available
  • large glycogen store
  • provides energy for high intensity activity


  • only 3 minutes of energy
  • PH decrease making a by product
  • not as quick as atp/pc
  • stimulates pain receptors
  • net effect is muscle fatigue
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