Krebs Cycle and Exercise Physiology Quiz
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Questions and Answers

What is the first intermediate produced in the Krebs Cycle?

  • Acetyl-CoA
  • Citrate (correct)
  • Oxaloacetate
  • Fumarate

    • How many NADH and FADH2 are produced in one cycle of the Krebs Cycle?

  • 4 NADH and 2 FADH2
  • 1 NADH and 3 FADH2
  • 3 NADH and 1 FADH2 (correct)
  • 2 NADH and 2 FADH2

    • What is the net ATP production from the complete oxidation of one molecule of palmitate?

  • 129 ATP (correct)
  • 12 ATP
  • 32 ATP
  • 33 ATP

    • What process occurs in the Electron Transport Chain?

    <p>Oxidative phosphorylation</p> Signup and view all the answers

    What is necessary for fatty acid oxidation to proceed in the Krebs Cycle?

    <p>Availability of oxaloacetate</p> Signup and view all the answers

    What is the recommended maximum percentage increase in exercise frequency, intensity, or duration per week?

    <p>10%</p> Signup and view all the answers

    In exercise progression at higher fitness levels, how will progressions typically occur?

    <p>By manipulating exercise intensity</p> Signup and view all the answers

    Which component of an aerobic training session comes first?

    <p>Warm-up</p> Signup and view all the answers

    What main benefit is associated with a light-intensity cool-down after exercise?

    <p>Aids in lactate clearance</p> Signup and view all the answers

    What is indicated for better glycogen resynthesis after exercise?

    <p>Passive cool-down</p> Signup and view all the answers

    What is the primary source of fuel during high-intensity exercise according to the crossover concept?

    <p>Carbohydrates</p> Signup and view all the answers

    How does epinephrine influence glycogen breakdown during exercise?

    <p>It increases cAMP levels, but requires increased Ca++ for breakdown</p> Signup and view all the answers

    What factors contribute to the crossover from fat to carbohydrate utilization during intense exercise?

    <p>Increased blood [lactic acid] and recruitment of fast-twitch fibers</p> Signup and view all the answers

    What is the consequence of high levels of lactic acid during exercise?

    <p>Decreased free fatty acid mobilization</p> Signup and view all the answers

    At what percentage of VO2max is fat mainly able to sustain energy substrate utilization?

    <p>60-75%</p> Signup and view all the answers

    What does the lactate threshold method primarily assess?

    <p>Degree of stress on the metabolic systems</p> Signup and view all the answers

    Which of the following factors is NOT considered when determining training duration?

    <p>Skill level</p> Signup and view all the answers

    What is a recommended frequency for training to achieve better results?

    <p>5 times a week</p> Signup and view all the answers

    In the context of training methods, what does 'interval training' focus on?

    <p>Specific work intervals followed by rest</p> Signup and view all the answers

    What might an increased training frequency of 6-7 times a week improve?

    <p>Skill and technique acquisition</p> Signup and view all the answers

    Which of the following statements is true regarding the relationship between intensity and stress on different systems?

    <p>A given degree of stress may not correlate across different physiological systems.</p> Signup and view all the answers

    What is the target heart rate (THR) calculated using the Karvonen method for an untrained individual with a resting heart rate (HR) of 65?

    <p>166 b/m</p> Signup and view all the answers

    What is a consideration for determining the duration of continuous training?

    <p>Length of continuous efforts</p> Signup and view all the answers

    How does training progress affect resting heart rate (HR)?

    <p>Resting HR decreases.</p> Signup and view all the answers

    Why is it suggested to prescribe exercise intensity based on percentages of current max capabilities like %VO2max?

    <p>It aligns with individual fitness levels.</p> Signup and view all the answers

    What could contribute to achieving better results with lower intensity training?

    <p>Increasing the volume of training</p> Signup and view all the answers

    Which heart rate method is associated with the most accurate regulation of intensity?

    <p>%VO2max method</p> Signup and view all the answers

    What happens to the pace needed to maintain a given target heart rate (THR) as a trained individual's resting HR decreases?

    <p>The pace increases.</p> Signup and view all the answers

    At a heart rate of 156, what percentage of VO2max is indicated?

    <p>75%</p> Signup and view all the answers

    How does the relationship between %VO2max and %HRR compare to that of %VO2max and %MHR?

    <p>One-to-one for %HRR and consistent for %MHR.</p> Signup and view all the answers

    What is the predicted maximum heart rate (HRmax) for a 21-year-old individual?

    <p>207</p> Signup and view all the answers

    What factors should be considered when determining exercise intensity, aside from intensity itself?

    <p>Mode, duration, and frequency</p> Signup and view all the answers

    Why is it important to monitor VO2 during exercise?

    <p>To relate it to the lactate threshold</p> Signup and view all the answers

    At what heart rate range does the correlation between HR and VO2 remain strong?

    <p>120-180 b/m</p> Signup and view all the answers

    What is the training-sensitive zone expressed as a percentage of HRmax?

    <p>60-90%</p> Signup and view all the answers

    How is Maximum Heart Rate (MHR) calculated?

    <p>MHR = 207 - (0.7 x age)</p> Signup and view all the answers

    What adaptations are expected from properly designed training practices?

    <p>Enhanced aerobic and anaerobic qualities</p> Signup and view all the answers

    What is primarily assessed to understand the intensity during exercise with available equipment?

    <p>Blood lactate concentration</p> Signup and view all the answers

    Which physiological response is associated with increased aerobic exercise intensity?

    <p>Increased stroke volume</p> Signup and view all the answers

    Study Notes

    Aerobic Power (VO2max) Definition

    • VO2max is the best index of cardiovascular fitness.
    • It represents the maximum capacity for oxygen uptake and ATP regeneration during exercise.

    VO2max Dependence

    • The ability of the cardiovascular system to deliver oxygen to the muscles.
    • The capacity of working muscles to extract and utilize oxygen to produce energy through aerobic metabolic pathways.
    • Mathematically, VO2max = COmax • a-vO2Dmax (where variables represent maximal cardiac output and arterial-venous oxygen difference).

    Aerobic Power (Continued)

    • It is important for sustaining high-intensity exercise because aerobic ATP synthesis rate depends on oxygen consumption rate.
    • More critical for endurance events (like a marathon or miler) than shorter high-intensity sprints (like a mile).

    VO2max During a Mile Race

    • Reaching VO2max (or more) during the final 400 meters of a mile race indicates high aerobic capacity.
    • This high capacity allows for high rates of ATP yield, supporting fast crossbridge cycling (fast-twitch muscle contraction).
    • It also permits supporting "aggressive" neuromuscular drive by an equivalent metabolic response.

    Glycolysis and Acidosis in Mile Racing

    • During a mile race, glycolysis significantly increases, leading to an increase in acidosis (lower pH) values.
    • Milers can better handle the resulting short-lived pH challenge due to their developed glycolytic buffering capacity.

    VO2max and Marathon

    • VO2max is a secondary factor in marathon success.
    • The slower yet fast pace of a marathon doesn't necessitate the same high rate of aerobic ATP synthesis as a mile race.
    • A higher lactate threshold expressed at a high percentage of VO2max is crucial for success.

    Best Competitor in Aerobic Events

    • The best competitor in aerobic events with similar VO2max values is typically the one who can sustain aerobic energy production at the highest percentage of their VO2max without accumulating large amounts of lactic acid in the muscles and blood.

    Lactate Threshold (LT) With Training

    • A higher percentage of VO2max for lactate threshold (LT) results in a higher pace needed to reach that threshold.
    • The higher the percentage, the better trained a person is considered to be.

    Aerobic Glycolysis

    • Involves initial glycolysis in the cytoplasm/sarcoplasm which proceeds to the mitochondria.
    • The Krebs Cycle and ETC play essential roles in this stage.
    • Net ATP from blood glucose is 32, and from muscle glycogen, it is 33.

    Krebs Cycle

    • Completes the oxidation of fuel nutrients.
    • Occurs in the mitochondrial matrix.
    • Continues pyruvate metabolism.
    • Consists of 8 steps including oxidation/reduction and decarboxylation leading to Citrate as first intermediate, and oxaloacetate as the last.
    • Generates 3 NADH and 1 FADH₂ per cycle.
    • Produces ATP through substrate-level phosphorylation.

    Electron Transport Chain (ETC)

    • Oxidative phosphorylation occurs in the ETC.
    • Oxidative reactions couple with the phosphorylation of ADP.
    • Phosphorylation of ADP is driven by oxidation of reduced electron carriers.

    Source of Reduced Electron Carriers

    • NADH and FADH₂ carry electrons to the ETC.
    • These are produced during glycolysis and the Krebs cycle.

    Electron Transport Chain Process

    • Electrons from NADH and FADH₂ move through the ETC .
    • This energy is used to pump H+ (protons) into the outer compartment of the mitochondria.
    • The H+ diffuses back to the inner compartment through ATP synthase (channels).
    • ATP synthase couples H+ movement to ATP production.
    • O₂ combines with H+ and electrons to form water.

    Lipid Metabolism

    • Fats are only metabolized aerobically.
    • Crucial roles for the Krebs Cycle, ETC and oxidation.
    • Net ATP production per molecule of palmitate is 129.
    • Fat oxidation in the Krebs Cycle is possible only when enough oxaloacetate is available.
    • Fats require the "flame" of carbohydrates for oxidation.

    Lipid Oxidation

    • Degradative pathway that is cyclic.
    • Cleaves 2 carbons from the fatty acid per cycle starting at the COOH end.
    • Releases 1, 2-carbon ACoA per cycle.
    • Produces 1 FADH₂ and 1 NADH per cycle.

    Substrate Utilization During Exercise (Crossover Concept)

    • During exercise, the body shifts from fatty acid use to carbohydrate use as intensity increases (cross-over).
    • The shift is due to FT fiber recruitment and increase in catecholamines/Calcium.

    Crossover Concept (Continued)

    • Glycolysis is accelerated by catecholamines and Calcium.
    • Increased glycolytic activity during intense exercise reduces the ability to utilize fat as fuel.
    • Lactate and H+ influence FFA (free fatty acid) mobilization from adipose cells.
    • Fat can only provide substrate at ~60-75% VO2max

    Determining Training Intensity (Most Important Variable)

    • An intensity threshold is needed for training adaptations and performance gains.
    • Factors other than intensity, like mode, duration, and frequency, matter in training.

    Determining Intensity (Continued)

    • Competition occurs around (and beyond) the lactate threshold, especially during sustained high-intensity efforts.
    • Training should improve both aerobic and anaerobic qualities (i.e., both mitochondrial and sarcoplasmic reactions).

    Intensity Regulation

    • Accurate intensity regulation involves recording VO2 during exercise (to evaluate the percentage of VO2max).
    • Assessing blood lactate concentration is important to understand how training intensity relates to the lactate threshold.
    • Heart rate can be used when equipment is not available.
    • HR correlates with metabolic rate (VO2).

    HR Methods (Various)

    • Percentage of maximum heart rate (MHR) method.
    • The Karvonen method (based on heart rate reserve- HRR), for determining training intensity.
    • Both HRR and MHR methods need factors (e.g., trained state or training session stage) to be considered.
    • Training intensity zones can be re-computed based on changes in resting heart rate.

    Lactate Threshold Method

    • A training and competition intensity measure.
    • Train at a near-lactate threshold HR (or pace).

    Determining Duration (Principles and Factors)

    • Duration depends on many variables like training method, intensity, volume, and the training phase one is in.

    Components of an Aerobic Training Session

    • Warm-up: Warm-up, stretching, and calisthenics.
    • Workout/Competition
    • Cool-down: Light-intensity exercises and stretching to aid recovery.

    Active vs. Passive Cooldowns

    • No difference in lactate clearance between active or passive cooldowns for an hour after exercise.
    • Passive cooldowns promote greater glycogen resynthesis.
    • Glycogen resynthesis principles should be considered for athletes in tournaments or training.

    Determining Exercise Progression

    • Exercise frequency, intensity, or duration should increase gradually (no more than 10% each week for athletes).
    • At higher fitness levels, incrementing frequency or duration of workouts is less feasible.
    • Progress in training occurs through intensity manipulation whenever increasing either volume or duration is not feasible.

    Examples of Aerobic Exercise Progression

    • Example exercise sessions demonstrate volume load then intensity.
    • Example workouts are suggestive and should be customized to individual ability.

    Determining Frequency (Considerations)

    • Frequency of training (~5 times per week) may be useful for an athlete.
    • Dose response to exercise training is beneficial (training intensity, duration and frequency).
    • More training sessions are beneficial for lower intensity exercise or exercise with shorter durations if intensity/duration are not changed.

    Interaction Among Intensity, Frequency, and Duration

    • Aerobic training adaptations are more likely correlated with workout intensity and total work accomplished than the exercise sequence.
    • Adjusting frequency and duration depending on the workout intensity is helpful when total workout work is to be kept the same.
    • Adjusting workout duration and frequency can work interchangeably.

    Determining Exercise Progression

    • Exercise frequency, intensity, or duration should not increase by more than 10% every week.
    • At higher fitness levels, reaching a plateau in increasing frequency or duration will mean progression must proceed by increasing workout intensity.

    Physiological Differences (HR vs. Lactate Threshold)

    • HR method: intensity based on the cardiovascular stress.
    • Lactate threshold method: intensity based on metabolic stress.
    • A given intensity level of stress in one system doesn't guarantee the same level of stress in another system.

    Which HR Method to Use

    • Use percentages of current maximum capabilities to determine intensity, like %VO2max or %HRreserve.
    • Use the HR method that most accurately reflects the desired work intensity and level
    • Best is to determine a specific HR associated with a specific %VO2max.

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    Description

    Test your knowledge on the Krebs Cycle, electron transport chain, and principles of exercise physiology. This quiz covers key concepts including ATP production, fatty acid oxidation, and effective training strategies. Perfect for students and fitness enthusiasts looking to deepen their understanding of these biological processes.

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