Section A Notes


energy sources and systems

energy sources

·          Sources

-          Glucose – a carbohydrate, the main form of carbohydrate found dissolved in plasma and used as an energy source to resynthesize ATP by cells and muscles.

-          Glycogen – a carbohydrate, the stored form of carbohydrate that is found in muscles and the liver used as an energy source.

-          Triglycerides and fats – main form of stored fat used as a source.

-          Protein and lactate.

-          Phosphocreatine

·         Effects of high intensity activity on ATP and PC stores

-          ATP and PC levels decrease during exercise.

-          Insufficient Stores don’t fully recover and there is not enough ATP and PC being resnythesised in 30 seconds of rest.

-          During exercise ATP / PC is supplying energy, where the PC breakdown is for ATP resynthesis.

-          Then during recovery ATP / PC is resynthesized, but 30 seconds is insufficient recovery time to fully replenish as it takes 2-3 minutes for full recovery.

·         Energy sources and level of intensity

-          At low level of exercise energy comes from a mixture of fats and carbohydrates.

-          These are broken down aerobically, using oxygen and the aerobic system.

-          Glycolysis occurs to break glucose down, into pyruvate.

-          Beta oxidation breaks down tri-glycerides.

-          The Krebs cycle involves the oxidation of acetyl-coenzyme-A and citric acid production.

-          In the Electron transfer chain, water is formed with hydrogen ions.

-          At high levels of intensity carbohydrates are only energy source and as intensity increases, more carbohydrates are used.

-          At high intensities fat use is limited by oxygen availability as no fats used anaerobically.

-          Energy release from fats is slower / quick release of energy from carbohydrates.

-          Lactic Acid System has no oxygen and anaerobic glycolysis occurs, where glucose is broken down forming pyruvate and lactic acid formed.

the atp system

·         Adenosine triphosphate.

·         Immediately useable energy source for the first 0-2 seconds of exercise.

·         ATP à ADP = P = ENERGY

·         Breaking bonds creates energy.

the atp-pc system

·          ATP-PC system

-          Uses phosphocreatine.

-          PC à P + C + ENERGY

-          Breaking bonds creates energy.

-          Producing enough energy to resynthesize two molecules of ATP.

-          Used for the first 2 to 8 seconds of exercise.

-          PC stores take 3 minutes to replenish

·         Cons of PC the system

-          Limited stores of PC. 

-          High intensity exercise can only be completed for brief period of time (8 – 10 seconds.)

-          Full recovery takes up 2-3 minutes.

·         Pros of the PC system

-          Energy is released quickly and doesnt require oxygen. 

-          ATP is resynthesised quickly and the phosphocreatine stores recover quickly.

-          This allows high intensity exercise to


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