Identify the fuel sources used by the three energy systems and explain why each energy system uses its particular fuel source(s). (6 marks)
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- The ATP-PCr system uses phosphocreatine as fuel because PCr can rapidly donate a phosphate group to ADP to reform ATP without requiring oxygen.
- The glycolytic (lactic acid) system uses carbohydrates in the form of glucose (from blood) and glycogen (stored in muscles) because these can be quickly broken down anaerobically to produce ATP.
- The aerobic system can use carbohydrates, fats, and proteins as fuel sources because oxygen is available for complete breakdown of these nutrients through cellular respiration pathways.
- PCr is used for the ATP-PCr system due to its high concentration in muscle cells (five times that of ATP) allowing for quick energy availability.
- Carbohydrates are the only fuel source that can be metabolised without oxygen, making them essential for the glycolytic system during high-intensity activities.
- The aerobic system’s ability to use multiple fuel sources, particularly fat during lower intensities, allows for sustained energy production during prolonged activities when oxygen supply meets demand.
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Sample Answer
- The ATP-PCr system uses phosphocreatine as fuel because PCr can rapidly donate a phosphate group to ADP to reform ATP without requiring oxygen.
- The glycolytic (lactic acid) system uses carbohydrates in the form of glucose (from blood) and glycogen (stored in muscles) because these can be quickly broken down anaerobically to produce ATP.
- The aerobic system can use carbohydrates, fats, and proteins as fuel sources because oxygen is available for complete breakdown of these nutrients through cellular respiration pathways.
- PCr is used for the ATP-PCr system due to its high concentration in muscle cells (five times that of ATP) allowing for quick energy availability.
- Carbohydrates are the only fuel source that can be metabolised without oxygen, making them essential for the glycolytic system during high-intensity activities.
- The aerobic system’s ability to use multiple fuel sources, particularly fat during lower intensities, allows for sustained energy production during prolonged activities when oxygen supply meets demand.