all 3 energy systems

  • Created by: Jkeay
  • Created on: 07-01-15 10:51

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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3 ways to re-syntheise 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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pc system --phosphocreatine

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 pc system


  • 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)

  1. Glycogen is found stored in the liver and broken down by glycogen phosphorylase
  2. ATP is added to the system
  3. broken down glycogen produces glucose - 6 - phosphate
  4. Phosphofructokinase (PFK) is added to break down glucose - 6 - phosphate
  5. pyruvic acid is formed which also prodcues 2 ATP
  6. this is broken down by lactate dehydrogenase to form lactic acid
  7. 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 system


  • 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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aerobic system

  • the aerobic system breaks down glucose, glycogen and fats to provide energy
  • this takes place during coupled reactions
  • the energy produced is used to resynthesise ADP into ATP

The aerobic system uses oxygen

It completely breaks down glucose

It produces H20 and CO2 

The system has three stages:

  • Aerobic glycolysis
  • Kreb's cycle
  • Electron transport chain
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aerobic glycolysis stage 1

  • Glucose is broken down into pyruvic acid
  • The presence of oxygen inhibits the accumulation of lactic acid
  • Pyruvic acid combines with coenzyme A to form Acetyl CoA
  • Takes place in cytoplasm
  • Controlled by phosphofructokinase
  • Produces the energy for the resynthesis of 2 ATP
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kreb's cycle stage 2

  • Acetyl CoA combines with oxaloacetic acid to form citric acid 
  • Citric acid is further broken down

1). CO2 produced and removed via lungs

2). hydrogen atoms are removed (oxidation)

3). energy is produced to resynthesise two molecules of ATP

4). oxaloacetic acid is regenerated

  • Takes place in matrix of mitochondria
  • Produces byproduct of CO2
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electron transport chain stage 3

  • Hydrogen atoms combine with coenzymes NAD and FAD 
  • This forms NADH and FADH which are carried down electron transport chain
  • Here hydrogen is split into H+ and e-
  • ETC takes place in the cristae of mitochondria

1). hydrogen electron (e-) splits from hydrogen atom and travels down ETC

2). this provides energy to resynthesise 34 ATP

3). hydrogen ion (H+) combines with oxygen to form H2O (byproduct)

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energy calculations

Total energy provided by aerobic energy system is 38 ATP

  • 2 ATP from aerobic glycolysis
  • 2 ATP from Kreb's cycle
  • 34 ATP from Electron transport chain
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This was a great resource in helping me read ahead before learning the content in lesson! - Thank you! :-)

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