Which one of the following statements is true of enzyme catalysts? a. Their catalytic activity is independent of pH. b. They are generally equally active on D and L isomers of a given substrate. c. They can increase the equilibrium constant for a given reaction by a thousand fold or more. d. They can increase the reaction rate for a given reaction by a thousand fold or more. e. To be effective, they must be present at the same concentration as their substrate.

Which one of the following statements is true of enzyme catalysts? a. Their catalytic activity is independent of pH. b. They are generally equally active on D and L isomers of a given substrate. c. They can increase the equilibrium constant for a given reaction by a thousand fold or more. d. They can increase the reaction rate for a given reaction by a thousand fold or more. e. To be effective, they must be present at the same concentration as their substrate.

Concepts of Biology

1st Edition

ISBN:9781938168116

Author:Samantha Fowler, Rebecca Roush, James Wise

Publisher:Samantha Fowler, Rebecca Roush, James Wise

Chapter4: How Cells Obtain Energy

Section: Chapter Questions

Problem 5RQ: Which of the following is not true about enzymes? a. They are consumed by the reactions they...

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Which of the following statements helps best explain the reaction specificity of an enzyme? a) The shape and charge of the substrates are compatible with the active site of the enzyme. b) The free energy of the reactants is greater than the free energy of the products. c) The equilibrium constant of the reaction is much greater than 1. d) The concentration of the enzyme inside living cells is greater than the concentration of substrate.
Which of the following would best explain how an enzyme catalyzes two different reactions? A) The enzyme contains a-helices and B-pleated sheets. B) The enzyme is subject to cooperativity C) Either the enzyme has two distinct active sites or the substrates involved in the two reactions have very similar structures D) The enzyme is subject to competitive inhibition and allosteric regulation E) The enzyme is composed of at least two subunits
Which of the followingdescribe superior properties of enzymes (biological catalysts) over traditional chemical catalysts? a. They are mostly and generally operative under mild temperature, pressure, and pH conditions b. They are regulated only by substrate concentration c. They do not effect the reaction equilibrium, but lower the reaction's activation energy d. They are recycled at the end of the reaction Choose all that apply
Some cool enzyme (CE) catalyzes the conversion of compound F to compound A. Which of the following must be true of CE? a) CE can facilitate conversion of compound A into compound F. b) CE binds more tightly to the substrate F than to the product A. c) CE decreases the energy of the transition state between compounds F and A. d) CE facilitates net conversion of F to A whenever F is present.
Which of the following statements concerning enzymes is TRUE? a. Enzymes can increase the equilibrium constant of a reaction by 1000-fold. b. The activity of many enzymes can be regulated. c. Many enzymes are consumed in the reactions they catalyze. d. The rate of enzymatic catalysis is independent of pH.
Which of the following statements is/are true about enzyme-catalyzed reactions? A. The reaction is faster than the same reaction. B. The free energy change of the reaction is opposite from the reaction in the absence of the enzymes. C. The reaction always goes in the direction toward chemical equilibrium. D. A and B only E. A, B and C
Which of the following accurately describes how an enzyme functions? a. reduces the energy content of the products b. allows for the exothermic reaction of materials that are usually endothermic c. changes the reaction mechanism effectively reducing the activation energy d. shifts the equilibrium for the reaction
Which of the following is NOT true? a. For many enzymes, Vmax is essentially equal to k3. b. Km is the reaction rate at 1/2 Vmax. c. At steady state the formation of ES is equal to the breakdown of ES. d. A Lineweaver-Burke plot generates a straight line. e. An Eadie-Hofstee plot generates a straight line.
Which of the following is TRUE concerning the induced fit model of enzyme catalysis? * (One correct answer only) A. The active site can be influenced by molecules binding elsewhere on an enzyme B. The initial binding of enzyme and substrate is the most tightly bound conformation C. The induced fit must occur prior to the initial binding of enzyme and substrate in order for the reaction to proceed D. The binding of enzyme and substrate is weakest in the transition state
Enzymes work by at least three mechanisms. Which of the following is NOT a mechanism by which enzymes function? A. by putting reactants in close proximity to each other. B. by altering the free energy ( ΔG) of the reaction. C. by orienting the reactants so they are positioned to favour the transition state. D. by altering the immediate environment of the reactants to promote reactant interactions.
Which of the following is true for the induced-fit model of enzyme-substrate binding? A. The conformation of the enzyme’s active site changes when the enzyme binds to its substrate B. Stronger interactions between the enzyme and its substrate are formed as compared to the lock-and-key model of enzyme-substrate binding C. Both A and B D. Neither A nor B Which statement does not apply to transition states? A. only exist transiently (have lifetimes on the order of 10^-14 to 10^-13 seconds) B. differ in energy from the substrate by the activation energy C. Chemical bonds are in the process of being formed and broken. D. Many have been detected and purified experimentally.
Which of the following is true under the following conditions: an enzyme displaying Michaelis-Menten kinetics where the enzyme concentration is 10 nM, the substrate concentration is 45 mM, and the Km is 50 µM? a) The enzyme has low catalytic efficiency for the substrate. b)The rate of catalysis is near half-maximal velocity. c)The enzymatic reaction is near maximal velocity. d)Halving the substrate concentration has little effect on the catalytic rate. e) There is not enough information provided.