Biochemistry midterm

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Biochemistry midterm
2010-10-24 22:54:12
Chapter 5a

Midterm 1
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  1. What is a polar molecule?
    A polar molecule is one in which one end is partially positive and the other partially negative.
  2. What are the 3 types of non-covalent bonding?
    • Ionic interactions
    • hydrogen bonding
    • Van der Waals
  3. What are the 3 types of Van der Waals bonding?
    • dipole-dipole
    • dipole-induced dipole
    • induced dipole-induced dipole
  4. What is an ionic interaction?
    Ionic interactions occur between charged atoms or groups.
  5. What is Hydrogen Bonding?
    Water molecules hydrogen bond with each other. Four bonding attractions occur.
  6. What is the heat of vaporization?
    Energy to vaporize 1 mole of water at 1 atm
  7. What is heat capacity?
    Energy to change temperature by 1 degree C
  8. What are nonpolar molecules?
    Nonpolar molecules have no polar bonds or the bond dipoles cancel due to molecular geometry. These molecules do not form good attractions with the water molecule. They are insoluble and are said to be hydrophobic (water hating).
  9. What is a hypotonic solution?
    When there is too much salt on the outside of the cell, so the cell losses water and shrinks.
  10. What is the Lowry-Bronsted acid?
    The proton donor
  11. What is the Lowry-Bronsted base?
    The proton acceptor
  12. The Henderson-Hasselbalch (HH) equation is derived from?
    The equilibrium expression for a weak acid.
  13. What is a buffer?
    A solution that resists change when a small amount of strong acid or strong base is added.
  14. What is the primary buffer within cells?
    phosphate buffer
  15. What is a Zwitterion?
    A compound with both positive and negative charges.
  16. What is the inflection point?
    Equal moles of acid are equal to moles of salt
  17. What is the equivalence point?
    Equal amounts of acid and base are in a solution
  18. What is thermodynamics?
    The heat and energy transformations studied by thermodynamics take place in a system (defined by investigator) connected to the surroundings (the rest of the universe)
  19. What is a closed system?
    Energy exchanges between system and surroundings
  20. What is an open system?
    Matter and energy exchanged between system and surroundings
  21. What is the first law of thermodynamics?
    • Energy is neither created nor destroyed
    • deltaE = q+w
    • deltaE is the change in the internal energy and is a state function
    • q is heat
    • w is work
  22. What function at constant pressure, volume, and temperature?
    Biochemical systems
  23. What equation is used to find the change in enthalpy for a reaction?
    deltaH reactants = deltaH products - deltaH reactants

    • -deltaH is exothermic
    • +deltaH is endothermic
  24. What is the Second Law of Thermodynamics?
    • With a spontaneous reaction, the entropy of the universe increases.
    • deltaS univ = deltaS system + delta s surroundings
  25. What is the most useful thermodynamic function for predicting reaction spontaneously?
    Gibbs free energy change (deltaG)
  26. What happens in a spontaneous reaction?
    • Free energy decreases
    • deltaG is negative energy released by the reaction
    • said to be exergonic
  27. What happens in a nonspontaneous reaction?
    • Free energy increases
    • deltaG is positive energy absorbed by the reaction
    • said to be endergonic
  28. What is a coupled reaction?
    • Two reactions run as a pair.
    • One is endergonic and the other is exergonic.
    • Overall it is exergonic and the pair is spontaneous
  29. What provides the free energy to drive most endergonic reactions?
    Hydrolysis of ATP
  30. What is an alpha amino acid?
    • A carboxylic acid with an amino group on the carbon alpha to the carboxylic acid
    • The alpha carbon also has an R group side chain. (except glycine which has two H's)
  31. In amino acids, if the R group is not H, the AA can exist in two ________ forms.
  32. Two amino acids link to form what?
    a peptide bond
  33. What 4 groups are amino acids classified into?
    • nonpolar
    • polar
    • acidic
    • basic
  34. At physiological pH, the carboxyl group of amino acids is ________ charges and the amino group is _______ charged
    • negatively
    • positively
  35. What does the titration curve show?
    How the amine and carboxyl groups react with the hydrogen ion
  36. At low pH a nonacidic/nonbasic amino acid is what?
  37. When does the isoelectric point for an amino acid occur?
    When there is no net charge