Molec Biochem Ch 12

The following question(s) refer to the overall transformation: The Michaelis constant KMis defined as: (k-1 + k2)/k1 (k-1 + k1)/k2 ([P] + [E])/[ES] [ES] none of the above

(k-1 + k2)/k1

When [S] = KM, 0 = _______Vmax. 0.1 1 0.67 0.5 2

0.5

[S] = KM for a simple enzymatic reaction. When [S] is doubled, the rate becomes _____ Vmax. 1 0.1 0.67 0.5 2

0.67

Find the initial velocity for an enzymatic reaction when Vmax = 6.5 x 10-5 mol•sec-1, [S] = 3.0 x 10-3 M, and KM = 4.5 x 10-3 M. -not enough information is given to make this calculation. -2.6 x 10-5 mol•sec-1 -1.4 x 10-2 mol•sec-1 -8.7 x 10-3 mol•sec-1 -3.9 x 10-5 mol•sec-1

2.6 x 10-5 mol•sec-1

What is the velocity of a first-order reaction when the reactant concentration is 6 x 10-2 M and the rate constant is 8 x 103 sec-1? -4.8 x 102 M•sec-1 -1.33 x 105 M-1•sec-1 -not enough data are given to make this calculation -1.33 x 105 M•sec -7.5 x 10-2 M•sec

4.8 x 102 M•sec-1

Find kcat for a reaction in which Vmax is 4 x 10-4 mol•min-1 and the reaction mixture contains one microgram of enzyme (the molecular weight of the enzyme is 200,000 D). 2 x 10-14 min-1 8 x 109 min-1 4 x 108 min-1 2 x 10-11 min-1 8 x 107 min-1

8 x 107 min-1

In the graph shown which of the following statements is TRUE concerning the "plateau" region of the curve? -All the available substrate has been converted to product. -The enzymes active site is saturated. -The enzyme is in the tense state. -A and C. -A and B.

The enzymes active site is saturated.

The rate of the reaction 2AB is dependent on ______. substrate binding Ping Pong competitive inhibition unimolecular mixed inhibition rate constant [A]2 phosphorylation isozymes ES complex small KD bimolecular large KD

[A]2

The following question(s) refer to the overall transformation: For the reaction, the steady state assumption assumes that: -[P]>>[E] -[P] is constant -k-1>>k2 -[ES] is constant -[S] = [P]

[ES] is constant

In order for an enzymatic reaction obeying the Michaelis-Menten equation to reach 3/4 of its maximum velocity, -[S] would need to be 3KM -[S] would need to be 2KM -[S] would need to be 3/4KM -[S] would need to be 50% greater than KM -not enough information is given to make this calculation

[S] would need to be 3KM

A Lineweaver-Burk plot is also called: a linear plot a double-displacement plot a double reciprocal plot a Michaelis-Menten plot a sigmoidal plot

a double reciprocal plot

The following question(s) refer to the overall transformation: -The overall transformation is composed of two elementary reactions. -can be zeroth order in [S] if [S]>>[E] -may be described by the Michaelis-Menten equation if certain assumptions are made -all of the above -none of the above

all of the above

The 2AB reaction is ______. large KD rate constant phosphorylation unimolecular [A]2 isozymes bimolecular competitive inhibition mixed inhibition small KD substrate binding Ping Pong ES complex

bimolecular

Which expression containing the free energy of activation (∆G‡) is proportional to the rate of a reaction? ln(∆G‡ /RT) -∆G‡ /RT +∆G‡ /RT e(-∆G‡ /RT)

e(-∆G‡ /RT)

If the half-life of a given reaction is constant (not dependant upon the initial conditions), the reaction must be: second order zeroth order first order diffusion controlled enzyme catalyzed

first order

The following question(s) refer to the overall transformation: The most efficient enzymes have kcat/KM values that approach: k1 k-1 + k2 k-1 k2 10^12 M•s-1

k1

The KM can be considered to be the same as the dissociation constant KSfor E + S binding if: -kcat/KM is near the diffusion-controlled limit. -the turnover number is very large. -this statement cannot be completed because KM can never approximate KS. -ES E + P is fast compared to ES E + S. -k2 << k-1.

k2 << k-1.

An enzyme is considered to have evolved to its most efficient form if -KM is a large number -kcat/KM is a very small number -KM is a small number -kcat is a large number -kcat/KM is near the diffusion-controlled limit

kcat/KM is near the diffusion-controlled limit

Second-order reactions: -have smaller rate constants than first-order reactions. -are termolecular. -are quite rare. -occur when two reactants collide. -are always faster than first-order reactions.

occur when two reactants collide.

For a reaction A + B C, if the concentration of B is much larger than [A] so that [B] remains constant during the reaction while [A] is varied, the kinetics will be: enzymatic sigmoidal pseudo-first-order unimolecular zero-order

pseudo-first-order

A zero-order reaction's rate is dependent on the ______. bimolecular ES complex rate constant competitive inhibition unimolecular Ping Pong phosphorylation isozymes [A]2 large KD substrate binding mixed inhibition small KD

rate constant

KM is: -the rate at which the enzyme dissociates from the substrate. -the rate at which the enzyme binds the substrate. -a measure of the catalytic efficiency of the enzyme. -the [S] that half-saturates the enzyme. -the rate constant for the reaction ES E + P.

the [S] that half-saturates the enzyme.