Concept explainers
(a)
Interpretation :
The relative glycogen phosphorylase activity when neither AMP nor ATP is present should be estimated from figure 15.15.
Introduction:
Glycogen phosphorylase is an enzyme which catalyzes the rate limiting step in glucogenolysis. It converts glycogen in animals into glucose-1-phosphate. ATP and glucose-6-phosphate act as allosteric inhibitors for glycogen phosphorylase because they reduce the affinity of glycogen phosphorylase for its substrate, inorganic phosphate. ATP is the end product of the glycogen phosphorylase enzyme. And glucose-1-phosphate released is readily converted into glucose-6-phosphate and participate in ATP production pathways. AMP acts as an allosteric activator for glycogen phosphorylase.
(b)
Interpretation:
The relative glycogen phosphorylase activity when AMP is present should be estimated from the figure 15.15.
Introduction:
Glycogen phosphorylase is an enzyme which catalyzes the rate limiting step in glucogenolysis. It converts glycogen in animals into glucose-1-phosphate. ATP and glucose-6-phosphate act as allosteric inhibitors for glycogen phosphorylase because they reduce the affinity of glycogen phosphorylase for its substrate, inorganic phosphate. ATP is the end product of the glycogen phosphorylase enzyme. And glucose-1-phosphate released is readily converted into glucose-6-phosphate and participate in ATP production pathways. AMP acts as an allosteric activator for glycogen phosphorylase.
(c)
Interpretation :
The relative glycogen phosphorylase activity when ATP is present should be estimated from the figure 15.15.
Introduction:
Glycogen phosphorylase is an enzyme which catalyzes the rate limiting step in glucogenolysis. It converts glycogen in animals into glucose-1-phosphate. ATP and glucose-6-phosphate act as allosteric inhibitors for glycogen phosphorylase because they reduce the affinity of glycogen phosphorylase for its substrate, inorganic phosphate. ATP is the end product of the glycogen phosphorylase enzyme. And glucose-1-phosphate released is readily converted into glucose-6-phosphate and participate in ATP production pathways. AMP acts as an allosteric activator for glycogen phosphorylase.
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Chapter 15 Solutions
Biochemistry
- Answers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book. Graphical Analysis of MWC Allosteric Enzyme Kinetics (Integrates with Chapter 1.1) Draw both Line weaver-Burk plots and Hanes-Woolf plots for an MWC allosteric enzyme system, showing separate curves for the kinetic response in (a) the absence of any effectors, (b) the presence of allosteric activator Λ, and (c) the presence of allosteric inhibitor I.arrow_forwardAnswers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book. Calculating C°' and from KeqCellular Concentrations Hexokinase catalyzes the phosphorylation of glucose from ATP. yielding glucose- 6-P and ADP. The standard-stale free energy change for hydrolysis of glucose-6-Ρ is — 13.9 kJ/mol. Calculate the standard-state free energy change and equilibrium constant for the hexokinase reaction.arrow_forwardAnswers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book. Quantitative Relationships Between Rate Constants to Calculate Km, Kinetic Efficiency (kcat/Km) and Vmax - III The citric acid cycle enzyme fumarase catalyzes the conversion of fumarate to form malate. Fumarate+H2OmalateThe turnover number, kcat, for fumarase is 800/sec. The Km of fumarase for its substrate fumarate is 5M. a. In an experiment using 2 nanomole/mL of fumarase, what is Vmax? b. The cellular concentration of fumarate is 47.5 M. What is v when [fumarate] = 47.5 M? c. What is the catalytic efficiency of fumarase? d. Does fumarase approach catalytic perfection?arrow_forward
- Answers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book. Graphical Analysis of Negative Gooperativity in KNF Allosteric Enzyme Kinetics The KNF model for allosteric transitions includes the possibility of negative cooperativity Draw Lineweaver-Burk and Hanes-Woolf plots for the case of negative cooperatively m substrate binding. (As a point of reference, include a line showing the classic Michaelis-Menten response of v to [S].)arrow_forwardAnswers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book. Quantitative Relationships Between Rale Constants to Calculate Km, Kinetic Efficiency (kcat/Km) and Vmax - II Triose phosphate isomerase catalyzes the conversion of glyceraldehyde-3-phosphate to dihydroxy-acetone phosphate. Glyceraldehyde3PdihydroxyacetonePThe Km of this enzyme tor its substrate glyceraldehyde-3-phosphate is 1.8 10-5 M. When [glyceraldehydes-3-phosphate] = 30 M, the rate of the reaction, v, was 82.5 mol mL-1 sec-1. a. What is Vmax for this enzyme? b. Assuming 3 nanomoles per mL of enzyme was used in this experiment ([Etotal]) = 3 nanomol/mL), what is kcat for this enzyme? c. What is the catalytic efficiency (kcat/Km) for triose phosphate isomerase? d. Does the value of kcat/Km reveal whether triose phosphate isomerase approaches catalytic perfection? e. What determines the ultimate speed limit of an enzyme-catalyzed reaction? That is, what is it that imposes the physical limit on kinetic perfection?arrow_forwardAnswers to all problems are at the end οΓthis book. Detailed solutions are available in the Student Solutions Manual. Study Guide, and Problems Book. Calculation of Rate Enhancement from Energies of Activation The relationships between the free energy terms defined in the solution to Problem 4 earlier are shown in the following figure. If the energy of the ES complex is 10 kJ/mol lower than the energy of E + S, the value of Ge:is 20 kJ/mol, and the value of Ge:is 90 kJ/mol what is the rate enhancement achieved by an enzyme in this case?arrow_forward
- Answers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book. Using Graphical Methods to Derive the Kinetic Constants for an Ordered, Single-Displacement Reaction The general rate equation for an ordered, single-displacement reaction where A is the leading substrate is v=Vmax[ A ][ B ](KsAKmB+KmA[ B ]+KmB[ A ]+[ A ][ B ])Write the Lineweaver-Burk (double-reciprocal) equivalent of this equation and from it calculate algebraic expressions for the following: a. The slope b. The y-intercepts c. The horizontal and vertical coordinates of the point of intersection when 1/v is plotted versus 1/[B] at various fixed concentrations of Aarrow_forwardAnswers to all problems are at the end οΓthis book. Detailed solutions are available in the Student Solutions Manual. Study Guide, and Problems Book. Using Site-Direcled Muta.nts to Understand an Enzyme Mechanism In this chapter, the exponent in which Craik and Rutter replaced Asp102 with Asn in trypsin (reducing activity 10,000 -fold) was discussed. On the basis of your knowledge of the catalytic triad structure in trypsin, suggest a structure for the “uncatalytic triad of Asn-His-Ser in this mutant enzyme. Explain why the structure you have proposed explains the reduced activity of the mutant trypsin. See the original journal articles (Sprang, et al., 1987. Science 237:905-913) to Craik, et al., 1987. Scieence 237:909-913) to see Craik and Rutter's answer to this question.arrow_forwardAnswers to all problems are at the end οΓthis book. Detailed solutions are available in the Student Solutions Manual. Study Guide, and Problems Book. Comparison of Emzymatic and Nonenzymatic Rate Constants The for alkaline phosphatase—catalyzed hydrolysis of melhylphoiphate is approximately 14/sec at pH 8 and 25ºC. The rate constant for the uncatalyzed hydrolysis of methyl phosphate under the same conditions is approximately I0-15/sec. What is the difference in the free energies of activation of these two reactions?arrow_forward
- Answers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book. Determining the Branch Points and Reducing Ends of Amylopectin A 0.2-g sample of amylopectin was analyzed to determine the fraction of the total glucose residues, that are branch points in the structure. The sample was exhaustively methylated and then digested, yielding 50-mol of 2,3-dimethylgluetose and 0.4 mol of 1,2,3,6- letramethylglucose. What fraction of the total residues are branch points? I low many reducing ends does this sample of amylopectin have?arrow_forwardAnswers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book. Describe the Effects on cAMP and Glycogen Levels in Cells Exposed to Cholera Toxin Cholera toxin is an enzyme that covalently modifies the G-subunit of G proteins. (Cholera toxin catalyzes the transfer of ADP-ribose from NAD+ to an arginine residue in Gan ADP-ribosylation reaction.) Covalent modification of G� inactivates its GTPase activity. Predict the consequences of cholera to.vin on cellular cAMP and glycogen levels.arrow_forwardAnswers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book. Determining the Free Energy of a Galactose Gradient Calculate the free energy difference at 25 C due to a galactose gradient across a membrane, if the concentration on side 1 is 2mM and the concentration on side 2 is 10mMarrow_forward
- BiochemistryBiochemistryISBN:9781305577206Author:Reginald H. Garrett, Charles M. GrishamPublisher:Cengage Learning