Lecture 11/23/14

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Lecture 11/23/14
2014-12-11 17:47:42
BME 221

BME 221
Show Answers:

  1. What are catalysts? do they effect the equilibrium position?
    Catalysts are a group of substances that speeds up the rate of the reaction but is not used up. It does not change the position of equilibrium or the ∆G of the reaction.
  2. For a reaction that generates net gas, how does the reaction equilibrium change and why
    • We can see (also from Le Chatelier’s Principle), for a reaction that generates net gas, increase the pressure will shift the reaction to the left.
    • WHY?
  3. What is Kd? What does a smaller Kd mean?
    • Kd is the concentration when half of the receptor is bound by the ligand.
    • A smaller Kd means that the ligands binds tighter to the receptor.
  4. What is the purpose of isothermal titration calorimetry?
  5. Draw the isothermal titration calorimetry setup, label all items (including power control - mention what it's purpose is)
    • A power control circuit keeps the sample cell at the exact same temperature as the reference cell, hence the reaction is carried out at constant temperature (isothermal).
  6. How can n and Ka be extracted from isothermal titration calorimetry?
    The n and Ka can be extracted using curve-fitting techniques.
  7. Define bioenergetics:
    Bioenergetics is the study of energy transformation in living systems.
  8. What is the main difference in the standard state between general/physical chemical chemistry and biochemistry? Give a specifics on the difference and the reasoning this exists
    • The standard state for ideal solutions.
    • General Chemistry: All the reactants and products are at unit molar concentration.
    • Biochemistry: All the reactants and products are at unit molar concentration, except hydrogen ion, of which the standard state is defined at 10^−7 mol/L.
    • This is because the physiological pH is about 7 and the concentration of hydrogen ion is around10−7 mol/L. Consequently, the change in the standard Gibbs free energy according to these two conventions will be different for reaction involving uptake or liberation of hydrogen ions (changes pH), depending on which convention is used.
  9. Explain ATP as energy currency and how it generates energy from certain reactions
    The “High-energy phosphate” in ATP is not really a high energy bond; breaking the γ-anhydride bond requires energy input, too. However, the reason why hydrolysis of ATP releases energy isthat the phosphate in ADP as well as the free phosphate can be resonance stabilized, so the bondformation releases more energy than the required energy input to break the bonds. For the same reason, the β-anhydride bond in ADP and ATP are high energy bonds too.
  10. Explain the principles of coupling reactions and why it occurs
    Many chemical and biological reactions are endergonic and therefore are not spontaneous understandard state conditions. However, in some cases, these reactions can be carried out to an appreciable extent by coupling them with an exergonic reaction.
  11. How do you find the equilibrium constant of coupled reactions given the individual equilibrium constants? What about for Gibbs free energy change?
    More generally, the equilibrium constant of the coupled reaction is the product of the individual reactions; the Gibbs free energy change is the sum of the individual reactions.
  12. Glycolysis: important take home messages from pages 223-229
    • Oxidation of glucose in cells is not 100% efficient.
    • Doing the oxidation in multiple steps helps to achieve a “more-reversible” energy transfer process.
    • Multiple-step reactions also helps to slow down the oxidation