Energy Systems

Energy Systems

1. Aerobic

   • Glycolysis
     • Sarcoplasm of muscle cell
     • Breakdown of glucose to pyruvic acid
     • 2 molecules of ATP formed
   • Krebs Cycle
     • 2 acetyl groups diffuse into matrix of mitochondria
     • Complex cycle of reactions occur
     • Acetyl groups combine with oxaloacetic acid forming citric acid
     • Hydrogen removed from citric acid
     • Rearranged citric acid undergoes oxidative carboxylation
       • Carbon & Hydrogen given off
     • Carbon forms CO2, transported to lungs & exhaled. Hydrogen taken to electron transport chain
     • 2 more ATP molecules produced
   • Electron transport chain (ETC)
     • Hydrogen carried to ETC by hydrogen carriers
     • Occurs in cristae of mitochondria, hydrogen splits into ions & electrons; are charged with potential energy
     • Ions oxidised to form water, electrons provide energy to resynthesise ATP
     • 34 ATP molecules formed
   • 38 ATP produced
   • No fatiguing by-products
   • Lots of glycogen & triglyceride stores; exercise for long time
   • Complicated system; can't be used straight away. Takes time for oxygen to be available to meet demands of activity
   • Fatty acid transportation to muscles is low & requires 15% more oxygen to be broken down than glycogen

2. Anaerobic Glycolytic/Lactic Acid

   • Provides energy for high intensity exercise longer than ATP-PC system
   • Anaerobic glycolysis takes place in sarcoplasm of muscle
     • When PC stores are low, glycogen phosphorylase activated to break down glycogen into glucose
       • Glucose further broken down into pyruvic acid by the enzyme PFK (phosphofructokinase)
         • Further broken down into lactic acid by lactate dehydrogenase
         • 2 ATP
   • 2 molecules of ATP produced for every molecule of glucose broken down
   • ATP can be resynthesised quickly due to few chemical reactions
   • Lasts longer than ATP-PC system
   • Lactic acid can be converted back to fuel in presence of oxygen
   • Can be used to produce extra burst of energy
   • Lactic acid as by-product. Denatures enzymes & prevents increasing rate of chemical reactions
   • Only small amount of energy can be released from glycogen under anaerobic conditions (5%)
   • How lactic acid can be removed
     • Sweat
     • Urine
     • Oxidised back to pyruvic acid
     • Liver (Cori cycle)

3. ATP/PC

   • Uses phosphocreatine (PC) as fuel
     • Energy rich compound
     • Can be broken down quickly by creatine kinase & easily to release energy to resynthesise ATP (Adenosine Triphosphate)
   • Short, fast release of energy
     • 5-8 seconds
   • Anaerobic process
   • ATP resynthesised when enzyme creatine kinase detects high levels of ADP (Adenoside Diphosphate)
   • Breaks down PC in muscles to phosphate and creatine, releasing energy
   • Energy -> Pi (phosphate) + ADP -> ATP
   • Every molecule of PC broken down, 1 molecule of ATP created
   • ATP can be resynthesised rapidly using ATP-PC system
   • PC stores resynthesised quickly (30s = 50%, 3 mins = 100%)
   • No fatiguing by-products
   • Can extend time ATP-PC system can be utilised through creatine supplementation
   • Limited PC supply - only 10 sec worth
   • Only 1 molecule of ATP can be resynthesised for every molecule of PC
   • PC resynthesis only occurs when oxygen is present