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Bioenergetics I and II

Bioenergetics I and II. Terminology Energetics Exergonic and endergonic reactions Enzymes Energy sources Immediate Nonoxidative Oxidative Immediate energy sources. Terminology. Energy – the capacity to do work Work – the product of force times distance

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Bioenergetics I and II

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  1. Bioenergetics I and II • Terminology • Energetics • Exergonic and endergonic reactions • Enzymes • Energy sources • Immediate • Nonoxidative • Oxidative • Immediate energy sources

  2. Terminology Energy – the capacity to do work Work – the product of force times distance Power – the rate of work, or work/time Heat – released during biological reactions; not used to perform work in biological systems Turnover – energy molecules continuously used and restored

  3. System/surroundings/universe Energy balance for an organism: Energy in (food) = Energy out (work) + Energy out (heat) + Energy stored (fat) Brooks et al.

  4. Energetics First law of thermodynamics: energy can neither be created or destroyed; it can be exchanged Second law of thermodynamics: processes always go in the direction of organization to randomness or disorder (entropy) thus, a change in energy, or enthalpy (ΔH) = change in free energy (ΔG) + change in entropy (TΔS) e.g., during concentric exercise (e.g., riding a cycle ergometer), ~25% of the energy consumed is used for useful work and ~75% is lost as heat

  5. Energetics Equilibrium constant (K'eq) – the ratio of concentrations of products to reactants at equilibrium For reaction A + B ↔ C + D, K'eq = [C][D]/[A][B] Gibbs’ free energy (ΔG) ΔGo' = −2.3 RT log K'eq The standard free energy change when the reactants are present in a concentration of 1.0 M and the pH is 7.0. R is the gas constant and T is the absolute temperature (Kelvin).

  6. Endergonic and exergonic reactions Endergonic reaction – a reaction accompanied by a gain in free energy - +ΔGo' Exergonic reaction – a reaction accompanied by a loss in free energy - −ΔGo'

  7. Endergonic and exergonic reactions Brooks et al.

  8. Endergonic and exergonic reactions Exergonic-endergonic coupling Murray et al., Harper’s Biochemistry, Appleton & Lange, 1996

  9. Endergonic and exergonic reactions Exergonic-endergonic coupling using a high-energy intermediate compound (e.g., ATP) Murray et al., Harper’s Biochemistry, Appleton & Lange, 1996

  10. Endergonic and exergonic reactions Exergonic-endergonic coupling Murray et al., Harper’s Biochemistry, Appleton & Lange, 1996

  11. Endergonic and exergonic reactions • Functionally speaking, this reaction will not occur because it is endergonic. If you should calculate the K’eq, it is ~0.00115.

  12. Endergonic and exergonic reactions • Functionally speaking, this reaction will not occur because it is endergonic. If you should calculate the K’eq, it is ~0.00115. • Calculated standard free energy of ATP to ADP is highly exergonic, and may be as high as -12 under cellular ionic conditions.

  13. Endergonic and exergonic reactions • Functionally speaking, this reaction will not occur because it is endergonic. If you should calculate the K’eq, it is ~0.00115. • Calculated standard free energy of ATP to ADP is highly exergonic, and may be as high as -12 under cellular ionic conditions. • Coupling the endergonic and exergonic reactions produces a favorable standard free energy change, and functionally alters the K’eq by a factor of 108.

  14. Enzymes Enzymes are proteins that catalyze chemical reactions by lowering the activation energy without undergoing permanent change. Components of typical enzymes: (a) substrate binding site(s); (b) coenzyme, e.g., NAD+, binding site(s); (c) allosteric binding site(s) (positive and negative)

  15. Enzymes Brooks et al.

  16. Enzymes Michaelis-Menten equation: vi = Vmax[S]/Km + [S] Brooks et al.

  17. Enzymes Significance of the Km Brooks et al.

  18. Enzymes Mechanisms of enzyme regulation Murray et al., Harper’s Biochemistry, Appleton & Lange, 1996

  19. Heat and temperature Q10effect Brooks et al.

  20. Energy sources for exercise The primary function of the metabolic pathways in the muscles during exercise is to maintain [ATP].

  21. Adenosine triphosphate (ATP): the common intermediate High energy adenosine phosphates: ATP ADP AMP (not to be confused with cyclic AMP) Brooks et al.

  22. Energy sources for exercise The primary function of the metabolic pathways in the muscles during exercise is to maintain [ATP]. The three general metabolic mechanisms for accomplishing this are: 1. immediate (phosphagens) 2. non-oxidative (glycolytic) 3. oxidative (aerobic)

  23. Energy sources for exercise Brooks et al.

  24. Energy sources for exercise Brooks et al.

  25. Energy sources for exercise - immediate

  26. Energy sources for exercise - immediate Brooks et al.

  27. Energy sources for exercise - immediate Kushmerick, Handbook of Physiology, 1983

  28. Energy sources for exercise - immediate Terjung et al., J Exp Biol, 115: 307, 1985

  29. Energy sources for exercise - immediate Brooks et al.

  30. Energy sources for exercise Adenylate energy charge (AEC)AEC = ½ (2[ATP] + [ADP]/[ATP] + [ADP] + [AMP]) If all adenine nucleotides are in the form of ATP, AEC = 1.0 If all are in the form of AMP, AEC = 0 Brooks et al.

  31. Energy sources for exercise - immediate Brooks et al.

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