CSCS CSCS: Bioenergetics of Exercise & Training 2 — Questions and Answers
Question 1: Which enzyme catalyzes the conversion of pyruvate to acetyl-CoA, linking glycolysis to the Krebs cycle?
- Pyruvate kinase
- Pyruvate dehydrogenase (Correct answer)
- Phosphofructokinase
- Lactate dehydrogenase
Correct answer: Pyruvate dehydrogenase
Pyruvate dehydrogenase converts pyruvate to acetyl-CoA in the mitochondrial matrix, allowing aerobic carbohydrate oxidation to continue.
Question 2: The oxygen deficit is best described as the difference between:
- VO2max and resting VO2
- Oxygen consumed and oxygen returned post-exercise
- Oxygen required and oxygen consumed during early exercise (Correct answer)
- EPOC and steady-state oxygen uptake
Correct answer: Oxygen required and oxygen consumed during early exercise
Oxygen deficit is the gap between the oxygen theoretically required and the oxygen actually consumed during the initial non-steady-state phase of exercise.
Question 3: At what blood lactate concentration (mmol/L) is the lactate threshold (LT) classically defined in many laboratory protocols?
- 1 mmol/L
- 2 mmol/L
- 4 mmol/L (Correct answer)
- 6 mmol/L
Correct answer: 4 mmol/L
The 4 mmol/L fixed blood lactate threshold (often called OBLA) is a widely used marker in laboratory settings, though individual thresholds vary.
Question 4: Which of the following best explains why beta-oxidation is considered highly efficient for energy production?
- It produces ATP faster than glycolysis
- It requires no oxygen
- It yields significantly more ATP per gram than carbohydrate (Correct answer)
- It occurs in the cytoplasm, reducing transport costs
Correct answer: It yields significantly more ATP per gram than carbohydrate
Fat yields approximately 9 kcal/g versus 4 kcal/g for carbohydrate, resulting in more total ATP per gram during beta-oxidation.
Question 5: During maximal sprint exercise lasting approximately 6 seconds, which energy system contributes the greatest percentage of ATP?
- Glycolytic system
- Oxidative phosphorylation
- Phosphagen (ATP-PCr) system (Correct answer)
- Beta-oxidation
Correct answer: Phosphagen (ATP-PCr) system
The phosphagen system dominates ATP production during maximal efforts lasting ~6 seconds due to the immediate availability of PCr.
Question 6: Which metabolic byproduct of anaerobic glycolysis directly inhibits phosphofructokinase (PFK)?
- Lactate
- ATP
- Hydrogen ions (H+) (Correct answer)
- AMP
Correct answer: Hydrogen ions (H+)
Accumulation of hydrogen ions (decreased pH) inhibits PFK, which is the rate-limiting enzyme of glycolysis, slowing ATP production.
Question 7: An athlete performs repeated 30-second all-out sprints with 3-minute rest periods. Which adaptation most directly improves performance on later sprint bouts?
- Increased mitochondrial density
- Enhanced PCr resynthesis rate (Correct answer)
- Greater glycogen storage
- Improved fat oxidation capacity
Correct answer: Enhanced PCr resynthesis rate
PCr resynthesis during recovery is primarily aerobic, so enhanced aerobic capacity improves PCr recovery between sprint bouts.
CSCS CSCS: Bioenergetics of Exercise & Training 2
Which enzyme catalyzes the conversion of pyruvate to acetyl-CoA, linking glycolysis to the Krebs cycle?