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HMS, BM EQ-Bank 152

Describe the process of mobilising fat as a fuel source during submaximal exercise.   (5 marks)

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Sample Answer

  • During submaximal exercise, stored triglycerides are broken down into free fatty acids and glycerol in response to hormonal stimulation.
  • The mobilisation process is oxygen-dependent and requires specific enzymes which enables fatty acid transport across cellular membranes.
  • Specialised transport proteins actively move fatty acids across the mitochondrial membrane where energy production occurs.
  • Once inside the mitochondria, beta oxidation breaks down fatty acids producing acetyl-CoA.
  • This process provides substantial energy for prolonged submaximal exercise (< 65% VO2 max), yielding more ATP per molecule than glucose but requiring greater oxygen availability and processing time.
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Sample Answer

  • During submaximal exercise, stored triglycerides are broken down into free fatty acids and glycerol in response to hormonal stimulation.
  • The mobilisation process is oxygen-dependent and requires specific enzymes which enables fatty acid transport across cellular membranes.
  • Specialised transport proteins actively move fatty acids across the mitochondrial membrane where energy production occurs.
  • Once inside the mitochondria, beta oxidation breaks down fatty acids producing acetyl-CoA.
  • This process provides substantial energy for prolonged submaximal exercise (< 65% VO2 max), yielding more ATP per molecule than glucose but requiring greater oxygen availability and processing time.

HMS, BM EQ-Bank 151

Analyse how the availability of different fuel sources affects an athlete's performance in a 90-minute soccer match.   (6 marks)

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Sample Answer

  • The ATP-PCr system provides immediate energy for explosive sprints and tackles in the first few seconds of each high-intensity effort through stored creatine phosphate.
  • During the match, muscle glycogen serves as the primary fuel source, supporting both aerobic activity for general play and anaerobic bursts for sprinting or rapid directional changes.
  • As the match progresses and muscle glycogen becomes depleted, the body increasingly relies on fatty acid oxidation for energy production during lower intensity periods of play.
  • The maintenance of blood glucose levels through liver glycogen breakdown becomes crucial in the latter stages of the match to sustain both physical and mental performance.
  • Players often experience fatigue in the final 15 – 20 minutes of the match due to significant depletion of muscle glycogen stores, resulting in reduced sprint capacity and skill execution.
  • Athletes who engage in carbohydrate loading protocols prior to the match can increase their muscle glycogen stores by up to 50%, thereby delaying the onset of fatigue and maintaining performance intensity throughout the full 90 minutes.
Show Worked Solution

Sample Answer

  • The ATP-PCr system provides immediate energy for explosive sprints and tackles in the first few seconds of each high-intensity effort through stored creatine phosphate.
  • During the match, muscle glycogen serves as the primary fuel source, supporting both aerobic activity for general play and anaerobic bursts for sprinting or rapid directional changes.
  • As the match progresses and muscle glycogen becomes depleted, the body increasingly relies on fatty acid oxidation for energy production during lower intensity periods of play.
  • The maintenance of blood glucose levels through liver glycogen breakdown becomes crucial in the latter stages of the match to sustain both physical and mental performance.
  • Players often experience fatigue in the final 15 – 20 minutes of the match due to significant depletion of muscle glycogen stores, resulting in reduced sprint capacity and skill execution.
  • Athletes who engage in carbohydrate loading protocols prior to the match can increase their muscle glycogen stores by up to 50%, thereby delaying the onset of fatigue and maintaining performance intensity throughout the full 90 minutes.

HMS, BM EQ-Bank 150

Explain how glucose is used differently as a fuel source in the glycolytic and aerobic energy systems.   (4 marks)

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Sample Answer

Glycolytic System:

  • Breaks down glucose without oxygen in sarcoplasm
  • Produces 2 – 3 ATP molecules through rapid glycolysis
  • Results in lactic acid as by-product
  • Powers high-intensity exercise 10 – 60 seconds

Aerobic System:

  • Complete glucose breakdown with oxygen in mitochondria
  • Produces 36 – 38 ATP through Krebs cycle/electron transport chain
  • Results in CO2 and H2O as by-products
  • Powers prolonged exercise 2+ minutes
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Sample Answer

Glycolytic System:

  • Breaks down glucose without oxygen in sarcoplasm
  • Produces 2 – 3 ATP molecules through rapid glycolysis
  • Results in lactic acid as by-product
  • Powers high-intensity exercise 10 – 60 seconds

Aerobic System:

  • Complete glucose breakdown with oxygen in mitochondria
  • Produces 36 – 38 ATP through Krebs cycle/electron transport chain
  • Results in CO2 and H2O as by-products
  • Powers prolonged exercise 2+ minutes

HMS, BM EQ-Bank 149 MC

Which statement best describes why fatty acids cannot be the primary fuel source for high-intensity exercise?

  1. Fatty acids require too much oxygen for breakdown
  2. Fatty acids are not stored in muscle tissue
  3. Fatty acids produce less ATP than glucose
  4. Fatty acids are too complex to break down quickly
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Consider Option A:  Fatty acids require too much oxygen for breakdown

  • Fatty acid metabolism requires significant oxygen

Other Options:

  • B is incorrect: Fatty acids are stored as intramuscular triglycerides
  • C is incorrect: Fatty acids actually produce more ATP than glucose
  • D is incorrect: Complexity isn’t the primary limitation

HMS, BM EQ-Bank 148 MC

A marathon runner hits "the wall" after 30 km of running. Which fuel source has most likely been depleted?

  1. Creatine phosphate
  2. Blood glucose
  3. Muscle glycogen
  4. Plasma proteins
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Consider Option C:  Muscle glycogen

  • Muscle glycogen depletion occurs in prolonged exercise

Other Options:

  • A is incorrect: CP depletion occurs in seconds
  • B is incorrect: Blood glucose is maintained through liver glycogen
  • D is incorrect: Proteins are not a primary fuel source

HMS, BM EQ-Bank 144 MC

Which row correctly identifies the fuel source and duration of the ATP-PCr energy system?

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Consider Option B: Creatine Phosphate 0 – 10 seconds

  • CP is the fuel source and system operates 0 – 10 seconds

Other Options:

  • A is incorrect: Glucose is fuel for glycolytic system
  • C is incorrect: Fatty acids fuel aerobic system
  • D is incorrect: Duration is wrong for ATP-PCr system