Study Guide 2

Exercise Metaoblsim

1. What is Metabolism?

   • Metabolism refers to all biochemical processes that occur within an organism to maintain life. It encompasses catabolic reactions (breaking down molecules for energy) and anabolic reactions (building complex molecules from simpler ones).

2. REDOX Reactions in ATP Production

   • REDOX (Reduction-Oxidation) reactions are vital in cellular respiration for energy production

   1. NADH and FADH2:

      • NADH (Nicotinamide adenine dinucleotide) and FADH2 (Flavin adenine dinucleotide) are electron carriers that transport electrons to the electron transport chain.

      • Their importance lies in their role in generating ATP by donating electrons, ultimately leading to ATP synthesis through oxidative phosphorylation.

3. Function of Enzymes

   • Enzymes are biological catalysts that speed up chemical reactions in the body without being consumed.

   • Enzyme activity is influenced by temperature and pH (acidity).

   • Exercise Effects: During exercise, body temperature rises, which can enhance enzyme activity, but extreme temperatures can denature enzymes.

   • Acidity increases due to lactic acid production, potentially inhibiting enzyme function.

4. Rate Limiting Enzymes

   1. Concept: Rate limiting enzymes are those that control the speed of metabolic pathways.

   2. MAIN Rate Limiting Enzymes:

      • Phosphofructokinase (glycolysis)

      • Citrate synthase (Kreb's cycle)

      • Cytochrome oxidase (electron transport chain)

   3. Influences on Enzyme Activity: ATP, ADP, and H+ concentration can increase or decrease the function of these enzymes.

5. Major Energy Pathways

   1. High Energy Phosphates (e.g., ATP, Creatine Phosphate):

      • Input: ADP + Creatine Phosphate

      • Products: ATP, Creatine

      • ATP Yield: 1 ATP per reaction.

   2. Glycolysis:

      • Input: Glucose or glycogen

      • Products: Pyruvate, 2 ATP (net yield)

      • Substrates: Carbohydrates, glycogen, can enter here.

   3. Oxidative Phosphorylation:

      • Input: NADH, FADH2, O2

      • Products: ATP, water

      • ATP Yield: Up to 34 ATP per glucose molecule (aerobic).

6. Supplementing with Creatine Monohydrate

   • Creatine enhances the body’s ability to regenerate ATP, leading to improved performance in short-duration, high-intensity efforts by providing an immediate source of energy.

7. Conversion of Glucose/Glycogen to Lactate

   • This occurs through glycolysis when oxygen is limited (anaerobic conditions).

   1. Fates of Lactate:

      • Can be converted back to glucose in the liver (Cori cycle) or used as energy by muscles or heart cells.

8. Energy Investment and Harvesting in Glycolysis

   • Investment Phase: 2 ATP are consumed to phosphorylate glucose.

   • Harvesting Phase: 4 ATP are produced, yielding a net gain of 2 ATP.

9. Kreb’s Cycle Importance

   • Produces electron carriers (NADH and FADH2) for the electron transport chain.

   1. Inputs: Acetyl-CoA, NAD+, FAD, oxaloacetate.

10. Beta Oxidation

    • The process of breaking down fatty acids in the mitochondria to produce acetyl-CoA for energy production during aerobic metabolism.

11. Role of Lipase in Fat Oxidation

    • Lipase enzymes hydrolyze triglycerides in adipose tissue into glycerol and free fatty acids, allowing them to enter metabolic pathways for energy production.

12. From Triglycerides to Usable Energy

    1. Lipolysis: Breakdown of triglycerides into glycerol and fatty acids.

    2. Fatty acid activation: Fatty acids are converted to acyl-CoA.

    3. Beta oxidation: Fatty acids are oxidized, producing acetyl-CoA, NADH, and FADH2.

    4. Acetyl-CoA enters the Kreb's Cycle.

13. The Electron Transport Chain (ETC)

    1. Location: Inner mitochondrial membrane.

    2. Input: Electrons from NADH and FADH2, O2.

    3. Products: ATP and water.

    4. Limits to Function: Availability of substrates, proton gradient, and oxygen levels.

    5. Importance of Oxygen: Oxygen is the final electron acceptor, preventing the backup of the electron transport chain and allowing continuous ATP production. Combines with the low energy electrons at the end of the ETC and hydrogen, forming water

14. Which energy systmes are active in different sports?

    • 1500 m run - aerobic energy system

    • 1 mile run - aerobic energy system

    • Olympic Weightlifting - anaerobic energy system

    • 400 m dash - anaerobic energy system

15. Oxygen-deficit in Exercise

    • Refers to the lag in oxygen uptake at the start of exercise, resulting in anaerobic metabolism until steady-state aerobic metabolism is achieved.

16. Excess Post-exercise Oxygen Consumption (EPOC)

    • Refers to the increased rate of oxygen intake post-exercise to restore the body to its resting state.

    1. Slow Portion: Related to restoration processes (e.g., lactate clearance).

    2. Fast Portion: Related to the immediate recovery processes (e.g., resynthesis of phosphocreatine).

    3. What causes EPOC to be greater in HI exercise: High-intensity exercise leads to greater lactate accumulation, elevated body temperature, and increased heart rate, resulting in a higher EPOC compared to lower-intensity exercise.

17. ATP Production Estimates

    1. Aerobic Metabolism of Glucose: 36-38 ATP.

    2. Aerobic Metabolism of Glycogen: 36-39 ATP.

    3. Aerobic Metabolism of a 16-carbon fatty acid: Approximately 106 ATP.

    4. Only Glycolysis for Glucose: 2 ATP.

18. Differences in NADH and FADH2 ATP Yield

    • NADH produces more ATP per molecule (approximately 2.5 ATP) than FADH2 (approximately 1.5 ATP) due to different entry points in the ETC.

19. Lactate Threshold

    • The exercise intensity at which lactate starts to accumulate in the blood, indicating a switch to anaerobic metabolism.

    1. Ventilatory Threshold: The point at which ventilation increases disproportionately to oxygen consumption, often correlating with lactate threshold.

    2. These metrics help in designing training programs for athletes to improve performance.

20. Indicators of Reaching VO2 Max

    • Plateau in oxygen consumption, high RPE (Rate of Perceived Exertion), and increased blood lactate levels during incremental exercise testing.

21. Respiratory Exchange Ratio (RER): Ratio of CO2 production to O2 consumption; indicative of substrate utilization during steady-state exercise in which a value of 1.0 represents 100% carbohydrate metabolism and 0.7 represents 100% fat metabolsism

    1. RER = VCO2 produced / VO2 consumed.

    2. Indicates the predominant fuel source during exercise; RER close to 0.7 suggests fat oxidation, while values closer to 1.0 indicate carbohydrate oxidation.

22. "Fat Burns in the Flame of Carbohydrate"

    • This phrase indicates that carbohydrate metabolism is necessary for optimal fat oxidation; without carbohydrates, fat metabolism is impaired.

23. Define Resporatory Exchange Ratio

    • noninvasive technique that is commnly used to estimate the percent contribution of carbohydrate or fat to energy metabolism during exercise is the ration of the vokume of CO2 produced to the volume of O2 consumed

24. How do we use RER to understand what fuel we use in exercise?

    • When using R as a predictor of fuel utilization during exercise, the role that protein contributes to ATP production during exercise is ignored. This is reasonable because protein generally plays a small role as a substrate during physical activity. Therefore, the R during exercise is often termed a nonprotein R.

Muscle Physiology

1. Muscle Organization Diagram

   1. Levels of organization: Whole muscle, fascicles, muscle fibers (cells), myofibrils, sarcomeres.

   2. Coverings: Epimysium (outer), Perimysium (fascicle), Endomysium (fiber).

2. Structure of Muscle Fiber

   1. Cell Parts: Sarcolemma (cell membrane), myofibrils, nuclei, mitochondria, etc.

   2. Sarcomere Structure: Composed of actin (thin) and myosin (thick) filaments.

   3. During contraction, I-band shortens, H-zone decreases, A-band remains unchanged.

3. Excitation-Contraction Coupling

   • The sequence of events by which an action potential leads to muscle contraction.

   1. Sliding Filament Model: Myosin heads attach to actin, pulling actin filaments inward, resulting in muscle shortening.

4. Muscle Fiber Types

   1. Named based on contraction speed (slow or fast) and metabolic properties (oxidative vs. glycolytic).

      • Different characteristics define each type, such as fatigue resistance (Type I: endurance vs. Type II: power).

   2. Mysosin Head: The energy for muscle contraction is derived from the breakdown of ATP by the enzyme myosin ATPase, found on the myosin cross-bridge. This process produces ADP and inorganic phosphate (Pi), releasing energy that energizes the myosin cross-bridges to pull actin molecules over myosin, resulting in muscle shortening.

   3. Fatigue during Heavy Exercise: Primarily leads to Type II fiber fatigue.

   4. Long-Duration Submaximal Exercise Fatigue: More Type I fibers involved.

5. Motor Unit

   1. A motor neuron and all muscle fibers it innervates. Recruitment occurs based on the size principle: smaller, slower-twitch fibers are recruited first, followed by larger, faster-twitch fibers as needed.

6. Force Production Factors

   1. PAP (Post-activation Potentiation): Enhanced muscle performance due to a prior muscular contraction.

   2. Force-Velocity Relationship: Force exerted by a muscle varies with the speed of contraction.

   3. Length-Tension Relationship: Optimal overlap of actin and myosin provides maximum force production.