Human Physiology
15th Edition
ISBN: 9781259864629
Author: Fox, Stuart Ira
Publisher: Mcgraw-hill Education,
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Textbook Question
Chapter 4, Problem 2RA
Which of these statements about enzyme-catalyzed reactions is true?
a. The
b. The rate of all enzyme-catalyzed reactions is decreased when the pH is lowered from 7 to 2.
c. The rate of reaction is independent of substrate concentration.
d. Under given conditions of substrate concentration, pH, and temperature, the rate of product formation varies directly with enzyme concentration up to a maximum, at which point the rate cannot be increased further.
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Which of the following best explains why enzyme catalysis is affected by a change in pH?
A. Change in pH alters ionization states of serine in the active site involved in nucleophilic catalysis
B. The ionization states of his, asp and glu involved in acid/base catalysis are altered with change in pH
C. Change in pH alters ionization states of contact amino acids in the active site
D. All enzymes have optimum pH
Consider the Michaelis-Menten enzymes below and answer the following questions.
Kcat (s')
9.5*105 1.4*10*
2.5*102 1.0*107
5.0*10 8.0*10²
Enzyme Km (M)
A
В
a. Which enzyme has the highest affinity substrate? How do you know?
b. Which enzyme can convert the most substrate to product in a given period of time? How
do you know?
c. Which enzyme has the highest catalytic efficiency? How do you know?
Consider the following enzyme cartoons or structures carefully. Note active sites, presence of
cofactors, substrates, etc. and then answer the following questions with the applicable
numbers 1, 2, 3, 4, None or All. More than one number may apply.
3.
2.
1.
GO
Substrate
Enzyme
Substrate
Enzyme
Pepsin
Enolase
a. Example(s) of an allosteric enzyme
b. Example(s) of a proteolytic enzyme
c. Example(s) of an enzyme(s) with cofactor(s)
e. Example(s) of an enzyme(s) that could be impacted by an irreversible
competitor.
d. Example(s) of an enzyme(s) with a second site for feedback control.
f. Enzyme(s) definitely composed of two or more protein chains.
Chapter 4 Solutions
Human Physiology
Ch. 4 - Use the lock-and-key model to explain how enzymes...Ch. 4 - Explain how enzymes are named, and the nature of...Ch. 4 - Draw graphs to represent the effects of changes in...Ch. 4 - Prob. 4CPCh. 4 - Prob. 5aCPCh. 4 - Prob. 5bCPCh. 4 - Prob. 5cCPCh. 4 - Prob. 6aCPCh. 4 - Define the terms exergonic reaction and endergonic...Ch. 4 - Prob. 7aCP
Ch. 4 - Prob. 7bCPCh. 4 - Which of these statements about enzymes is...Ch. 4 - Which of these statements about enzyme-catalyzed...Ch. 4 - Which of these statements about lactate...Ch. 4 - In a metabolic pathway, a. the product of one...Ch. 4 - In an inborn error of metabolism,
a. a genetic...Ch. 4 - Which of these represents an endergonic...Ch. 4 - Which of these statements about ATP is true? a....Ch. 4 - When oxygen is combined with 2 hydrogens to make...Ch. 4 - Enzymes increase the rate of chemical reactions...Ch. 4 - According to the law of mass action, which of...Ch. 4 - Explain the relationship between an enzyme's...Ch. 4 - Explain how the rate of enzymatic reactions may be...Ch. 4 - Explain how end-product inhibition represents a...Ch. 4 - Prob. 14RACh. 4 - The coenzymes NAD and FAD can "shuttle" hydrogens...Ch. 4 - Prob. 16RACh. 4 - Why do we need to eat food containing niacin and...Ch. 4 - Metabolic pathways can be likened to intersecting...Ch. 4 - Prob. 19RACh. 4 - Suppose you come across a bottle of enzyme tablets...Ch. 4 - Describe the energy transformations that occur...Ch. 4 - Use the reversible reactions involving the...Ch. 4 - Use the graph here and in figure 4.4 to answer the...Ch. 4 - Use the graph here and in figure 4.4 to answer the...Ch. 4 - Prob. 25RACh. 4 - Prob. 26RACh. 4 - Prob. 27RA
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- Which of the following will happen if the concentration of an enzyme increases for a given substrate?? a. the reaction rate increases similarly b. the rate of the reaction decreases to a point. c. there is no change in the reaction. d. the turnover number decreases at the same rate that the enzyme concentration increases. e. the reaction stops.arrow_forwardWhich of the following statements about the Michaelis Menten constant (Km) is correct......A. can be determined by plotting the data v/[S] against 1/[S] B. A large Km indicates a low affinity between the enzyme and the substrate C. A large Km means that a large concentration of substrate is needed for the enzyme to work D. is a measure of the affinity of enzymes for proteins, minerals and vitamins E. Small Km means that a large concentration of substrate is needed for the enzyme to workarrow_forwardEvaluate the following statements concerning enzyme kinetics. Which one of the statements is false? a. Enzyme saturation fluctuates. b. In an uninhibited enzymatic reaction system, adding an excess of substrate will increase the reaction velocity beyond Vmax. c. The Vmax of an enzyme kinetics graph represents the point at which the enzyme is saturated with substrate. d. Non-competitive inhibition of an enzymatic reaction can be overcome by adding more unaltered enzyme. e. The activation energy of a reaction can be reduced by the presence of an enzyme.arrow_forward
- FoF1 ATPase is the enzyme that catalyzes ATP synthesis. The enzyme itself is deactivated by ATP. What mode of enzyme regulation is being exemplified? Select the correct response: Trasncriptional control Covalent modification Proteolytic modification Allosteric regulation Compartmentationarrow_forwardWhich of the following statement on the process of enzyme production is false? Select one: a. Agglomeration is sometimes used to increase solubility of enzyme powder b. After fermentation, intracellular enzymes can be directly extracted by filtration c. Spray drying can be used to dry the enzyme products into powder forms d. Chromatography is used to purify the enzyme producedarrow_forwardIndicate whether each of the following statements about an enzyme active site is true or false. a. It is the location where substrate molecules are produced. b. It always has a fixed, rigid geometry. c. It always has a geometrical shape exactly complementary to that of substrate. d. It always accomodates several structurally related substrates. e. It is the location where substrate molecules are converted to product molecules. f. It always has a shape that has a degree of flexibility to it. g. it always accomodates only one specific substrate.arrow_forward
- What is a limitation of the Michaelis-Menten kinetics? A. Enzymes have different binding sites which were not considered by the Michaelis-Menten assumption. B. Most enzymes are multimeric with many active sites. C. Variability in enzyme concentration due to synthesis and degradation by cells were not included in the Michaelis- Menten assumption. D. Enzymes have coenzymes that are involved in catalysis. E. Active sites can bind multiple substrates.arrow_forwardWhich 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.arrow_forwardWhen an enzyme catalyzes a reaction… A. The pH changes B. Substrate concentration is reduced C. Product concentration is reduced D. Substrate concentration is increasedarrow_forward
- Choose the statement that best explains WHY the aldol condensation is considered base-catalyzed. a The base lowers the activation energy of the intermediates. b The base is used throughout the reaction but not consumed in the reaction, since it is regenerated in the final steps. C The base deprotonates the ketone, generating the nucleophile. d The base reacts with any acid that is present in the solution, accelerating the rate.arrow_forwardWhich 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.arrow_forwardPlease complete the following question. There is no need to provide an explaination. 13arrow_forward
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