the reacting molecules must be brought together in exactly the right orientation in order for the reaction to take place ("effective collision")..
B.Enzymes reduce activation energy (Chap5. p. 167-69)
3. Random interactions lead to Enzyme-Substrate Complex formation (effective collision)
4. Enzymes reduce activation energy by
a. Increasing the number of effective collisions between substrates
c. Review steps of RNAse active site
d.Another example: Lysozyme: pg.170 Figure 5-28
a. See Table 5-2 p.169 for list of common enzyme group names and functions..
IV. Factors effecting Reactions (in general, including enzyme-mediated)(Back to Chapter 3)
A. Free energy considerations (as discussed earlier)
1. Free energy change must be negative
B. Concentration of the molecules in the system also determines whether a reaction will occur.
1. As the concentration of one molecule increases the reaction will move toward the production
of the other molecule (Le Chatlier's Principle).
C. BIG QUESTION - how much of a concentration difference is required to overcome a .G that
1. Rewrite .G to reflect concentration component
b. .G o is the Standard Free Energy change (1M @ pH=7) in kcal/mole
c. @37 o C d. Note that when [A] = [B], concentration effects are negated and .G=.G o (ln 1 = 0). D.
For a reversible reaction A ¡êB (see Figure. 3-20 p.92)
1. One direction is energetically favored (-.G) over the other
3. As A converts to B, the concentration effect of greater amounts of B begins to overcome the +"‘–"²ª› G (for B A), to a point where B A is equal to A B.
4. In Table 3-1 some calculations were done to determine when .G=0 (equilibrium),
that is when .G o = -0.616ln[B]/[A] (con't on next page).
5. It is important to note that it requires significant excess of the favored product (B) to push the reaction back to unfavored product (A).
6. Enzymes do not cha...