[試題] 101-2 陳振中 物理化學三 期末考
課程名稱︰物理化學三
課程性質︰必修
課程教師︰陳振中
開課學院：理學院
開課系所︰化學系
考試日期（年月日）︰2013.06.13
考試時限（分鐘）：10:20-12:30
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
1.A macromolecule has six sites for ligand L. An investigator is able to
measure three of the macroscopic dissociation constants for ligand binding,
K_1, K_4, K_5. He has finds that K_5=15K_1, and K_4=8K_1, where the subscript
indicates the number of ligand bound on the molecule. He then claims that this
result clearly demonstrates negative (anticooperative) site-site interactions,
an that the Scatchard plot for this system is surely concave-up, A critic
disagrees and says that the limited data indicate there are no site-site
interactions. Who is right, and why?
2. If every collision can make reaction occur, the reaction rate can be written
as Z_12 =<v_12> pi (d_12)^2 _1 _2, from which we have defined the rate constant as
k’= <v_12> pi (d_12)^2. Express this rate constant in the unit of mole per unit
time per unit volume.
3.Based on the Stokes-Einstein relationship, D=kT/(6r*eta), predict and explain
whether or not the diffusion controlled rate constant would depend on the
molecular radius for reactants of the same size.
4.Consider the following mechanism
X_1
↗ ↘
↙
E +S E + P
↘
↘ ↗
X_2
Let [E]_0 be the total enzyme concentration, and [S] be free substrate
concentration.
(a)Derive the expression for V=d[P]/dt in terms of [E]_0 and [S]. The following
reactions may be assumed to be at equilibrium while P is produced:
E + S ←→ X_1 K_1=[E][S]/[X_1]
E + S ←→ X_2 K_2=[E][S]/[X_2]
So that you need not use the usual steady-state assumption.
(b)Student A claims that the form of the rate law for Equation A is
indistinguishable from that for the traditional Michaelis-Menten mechanism.
He claims that this is true regardless of the relative values of k_2, k_2’,
K_1 and K_2 in Equation A. Student B claims that the concentration dependencies
for equation A and B are distinguishable only when k_2>>k_2’ and K_1<<K_2.
Student C says that the rate laws for the two mechanisms will have different
forms under any circumstances. Which student (if any) is correct? Why?
5.The major weakness if the simple hard-sphere collision theory of reactions
is that the hence derived equilibrium constant is not consistent with what we
expected in thermodynamics. Explain what the weakness is.
6.The cooperative order-disorder transition is a characteristic of proteins,
which can convert reversibly from native (N) to denatured(D) state. The process
to form the native state is known as protein folding. In the simple model,
protein folding can be described by the following two-state model:
k_1
→
N ← D
k_-1
In general, we would measure a physical property (y) of the protein, which has
different values for the N and D states. If we define the variable
△y = y – y_bar to indicate the difference of the exoerimental data
measured at time t and at equilibrium, develop a linear plot which can be
used as an evidence for the two-state model.
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