Ch 8.1-2 Text

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Ch 8.1-2 Text
2014-10-05 20:26:42
Test Two
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  1. ·       About a quarter of the genes in the human genome do what?
    ·         The most striking characteristics of enzymes are their __ and __. __ takes place at a particular site on the enzyme called the __
    ·         Nearly all known enzymes are __, which don’t have an absolute monopoly on catalysis; the discovery of catalyically __ suggests that __ was a __
    • encode enzymes
    • catalytic power and specificity
    • catalysis
    • active site
    • proteins
    • active RNA molecules
    • RNA was a biocatalyst
  2. ·         Proteins are highly effective catalysts because of what?

    ·         Enzymes bring substrates together in an __, the prelude to __ and __. They catalyze reactions by __, the highest-energy species in reaction pathways. By selectively stabilizing a transition state, an enzyme determines __
    • their capacity so specifically bind a very wide range of molecules
    • optimal orientation
    • making and breaking chemical bonds
    • stabilizing transition states
    • which one of several potential chemical reactions actually takes place.
  3. ·         Enzymes accelerate reactions because most reactions __.
    o   Ex: Carbonic anhydrase: __ is catalyzed by this. The __ would be less complete without it. Carbonic anhydrase hydrates 106 molecules of CO2 per second.
    ·         An enzyme usually does what, such as __, which catalyze __, the hydrolysis of a peptide bond. 
    • naturally occur slow
    • hydration of carbon dioxide
    • transfer of CO2 from the tissues to the blod and then to the air in the alveolaie
    • catalyzes a single chemical reaction or a set of closely related reactions
    • proteolytic enzymes, which catalyze proteolysis
  4. o   Proteolytic enzymes differ in their __
    §  Ex: __is undiscriminating and will cleave any peptide bond, but __ catalyzes the splitting of peptide bonds only on the carboxyl side of lysine and arginine
    §  DNA polymerase catalyzes __
    o   The specificity of an enzyme is due to the __, which is the result of the intricate 3D structure of the enzyme protein 
    • degree of substrate specificity
    • papain 
    • trypsin
    • addition of nucleotides
    • precise interaction of the substrate with the enzyme
  5. ·        Enzymes rely on __ for functioning . They can execute __ that can’t be performed by the __. An enzyme without a __is an __, while the complete, catalytically active enzyme is a __. 
    • cofactors 
    • chemical reactions
    • 20 amino acids
    • cofactor 
    • apoenzyme
    • haloenzyme
  6. The cofactors:

    o   Small organic molecules (__): can be __ or __ bound to enzyme
    §  Tightly bound= __

    Loosely bound= __

    o   One coenzyme can __, which may have a similar catalytic mechanism
    • Metals
    • coenzymes
    • tightly or loosely
    • prosthetic groups
    • cosubstrates because they bind and get released
    • bind to a variety of enzymes
  7. ·         A key activity in all living systems is the ability to __ (ex: enzyme pumps, conversion of ATP to do work, etc.)
    convert one form of energy into another with enzymes playing vital roles
  8. ·         Whether a reaction can take place depends on __ between reactants and products
    o   Free energy: __ 
    • energy differences
    • thermodynamic property that is a measure of useful energy, or the energy that is capable of doing work
  9. ·         For determining spontaneity, we need two things:
    __ and __
    • o   The free energy difference between the produts and reactants (determines whether spontaneous or not)
    • o   The energy required to initiate the conversion of reactants into products (determines rate)
  10. ·         A reaction can take place spontaneously if:
    o   ΔG is __; if positive,its __and energy is __
    o   Equilibrium (no net change if ΔG is zero)
    ·         ΔG depends only on the __minus the__. The ΔG is __ of the path (or molecular mechanism) of the transformation. The __ of a reaction has no effect on ΔG
    • negative (exergonic)
    • nonspontaneous 
    • required (endergonic)
    • free energy of the products 
    •  free energy of the reactants (initial)
    • independent
    • mechanism
  11. ·         The ΔG provides no information about the __. Even if a reaction is __, it may still have  a very low rate, which depends on the __
    ·         The ΔG of A+BàC+D will be __
    o   ΔGo is the __ (when the concentrations are 1, the pressure is 1 atm, and the temperature is 25oC) , R is the gas constant, T is the absolute temperature and [x] are the concentrations
    • rate of a reaction
    • spontaneous
    • free energy of activation
    • ΔG= ΔGo + RT ln ([C][D]/[A][B])
    • standard free energy change under standard conditions
  12. o   The standard state has a pH of__ denoted ΔGo
    §  A simple way to determine ΔGo’ is to __, where there is no net change in reactants and products and the reaction has stopped and ΔG=0
    • 7
    • measure the concentrations of reactants and products when the reaction has reached equilibrium
  13. · At 0, the reaction is set to zero; and, rearranging it to find the ΔGo’ gives:
    o   __
    · The equilibrium constant udner standard conditions, K’eq is equal to the __
    · Substituting this Keq for ln ([C][D]/[A][B]) gives :
    o   __, which can be rearranged to give K’eq= 10 ΔGo/RT; and, subbing in the R and T gives: K’eq=10^(- ΔGo’/2.47)
    • ΔGo’ = -RT ln ([C][D]/[A][B])
    • concentration of the products over the concentration of reactants
    • ΔGo’= -RT lnK’eq
  14. ·         It is important to stress that whether the ΔG for a reaction is larger, smaller, or the same as ΔGodepends on the __. The criterion for spontaneity is__, not __. 
    • concentrations of the reactants and products
    •  ΔG, not ΔGo’
  15. ·         Enzymes alter only the __ and not the __
    o   An enzyme can’t alter the __ and cannot alter the __
    o   Also, the __ is the same whether or not the enzyme is present but the amount of product formed in seconds when enzyme is present might take hours if the enzyme were absent
    • reaction rate
    • reaction equilibrium
    • laws of thermodynamics
    • equilibrium of the chemical reaction
    • amount of product formed
  16. o   Why does the rate of product formation level off with time?
    §  __
    The reaction has reached equilibrium. Substrate S is still being converted into product P, but P is being converted into S at a rate such that the amount of P present stays the same.
  17. §  The equilibrium constant K for the rate constants is:
    · __
    ·         Enzymes accelerate the __ but do not shift their positions. The equilibrium position is a function only of the __ 
    • Kforward / kreverse
    • attainment of equilibria
    • free-energy difference between reactants and products