Biochem Lecture 1

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  1. Covalent Bond
    A chemical bond that involves the sharing of electrons between two atoms
  2. Bond Dissociation Energy
    The energy required to break a chemical bond (a measure of bond strength)
  3. Hydrogen Bond
    An electrostatic interaction b/w an electronegative atom and the hydrogen atom covalently bonded to another electronegative atom
  4. Electronegativity
    Measures the ability of an atom to attract electrons to itself w/in a covalent bond
  5. Ionic Bond (Salt-Bridges)
    Electrostatic interation b/w 2 atoms or molecules w/ formal charges
  6. Hydrophobic Effect
    Describes the tendency of a non-polar solute to come together when placed in a polar environment
  7. Free Energy (G)
    The component of the total energy of a system that can do work at constant temperature and pressure
  8. Change in Free Energy (delta G)
    The amount of free energy released (-) or absorbed (+) in a reaction at constant temperature and pressure
  9. Spontaneous Reaction
    A rxn that, given a set of initial conditions, will proceed in the direction of the production of products to reach equilibrium
  10. Enthalpy (H)
    A measure of the heat conten of a given molecule or system
  11. Entropy (S)
    A measure of disorder and randomness
  12. Equilibrium
    The point in a chemical reaction where the rate of the forward reaction is equal to the rate of the reverse reaction
  13. Equilibrium Constant (Keq)
    The ratio of the concentration [] of products over the concentration of reactants once equilibruim has been achieved
  14. Two major classes of bonds
    • 1. Covalent bonds - generally unchanging in proteins
    • 2. Non-covalent bonds - 'weak' bonds that cause interactions b/w macromolecules
  15. Major Non-Covalent Bonds
    • Ionic bonds
    • Hydrogen bonds
    • Hydrophobic interation
    • Van der Waals interactions
  16. Conformation
    Changes about a single bond that are adopted w/out breaking covalent bonds (staggered, eclipsed, etc)
  17. Configuration
    changes about a double bond that can only be adopted by breaking bonds (cis and trans)
  18. E.N. Rankings
  19. Hydrogen Bond Acceptor
    The lone pair or partial negative charge (the e.n. atom other than H)
  20. Hydrogen Bond Donator
    The Hydrogen with the partial positive charge
  21. Formal Charge
    Arises when an atom has more (-) or less (+) valence electrons in the Lewis structure than the bare atom
  22. Oxygen Formal Charges
    • Bare Oxygen owns 6 electrons, so:
    • ~owns 7 if 1 bond = negative (anion)
    • ~owns 6 if 2 bonds = neutral
  23. Nitrogen Formal Charges
    • Bare Nitrogen owns 5 electrons, so:
    • ~owns 4 if 4 bonds = positive (cation)
    • ~owns 5 if 3 bonds = neutral
  24. Factors of Bond Dissociation Energy
    • Q= charge of the two ions
    • r = distance b/w the two ions
    • E = dielectric constant
  25. Dielectric Constant
    • The ability of a solvent to shield ions from each other.
    • ~E is HIGH for polar solvents
    • ~E is LOW for non-polar solvents
  26. Exergonic Reaction
    • Rxns with a negative delta G
    • Rxns that release free energy, spontaneous
  27. Endergonic Reaction
    • Rxns with a positive delta G
    • Rxns that absorb free energy, nonspontaneous
  28. Factors of Delta G
    Enthalpy (H), Entropy (S), and Temperature (assumed constant)
  29. Exothermic Reaction
    • Rxns with a negative delta H
    • Rxns that feel hot (temperature of surroundings is increased)
  30. Endothermic Reaction
    • Rxns with a positive delta H
    • Rxns that feel cold (temperature of surroundings is decreased)
  31. Increase in Entropy
    If the order in a system decreases, the change in entropy or degrees of freedom is positive
  32. Decrease in Entropy
    If the order in a system increases, the change in entropy or degrees of freedom is negative
  33. Large Keq
    Products will predominate at equilibrium
  34. Small Keq
    Reactants will predominate at equilibrium
Card Set
Biochem Lecture 1
Lecture 1 notes BC 351
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