Biochemistry
6th Edition
ISBN: 9781305577206
Author: Reginald H. Garrett, Charles M. Grisham
Publisher: Cengage Learning
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Chapter 16, Problem 2P
Interpretation Introduction
To determine:
At which step in the contraction cycle an ATP analog ß,?-methylene-ATP is capable of inhibiting muscle contraction.
Introduction:
Muscle contraction is a cyclic process in which actin and myosin proteins undergo conformational changes with the help of ATP. In the beginning of the cycle myosin head is energized and has bound ADP molecule and an inorganic phosphate group.
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- 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. 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 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_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. Quantitative Relationships Between Rate Constants to Calculate Km, Kinetic Efficiency (kcat/Km) and Vmax - I Measurement of the rate constants for a simple enzymatic reaction obeying Michaelis-Menten kinetics gave the following results: k1=2108M1sec1k1=1103sec1k2=5103sec1a. What is Ks, the dissociation constant for the enzyme-substrate complex? b. What is Km, the Michaelis constant for this enzyme? c. What is kcat (the turnover number) for this enzyme? d. What is the catalytic efficiency (kcat/Km) for this enzyme? e. Does this enzyme approach kinetic perfection? (That is, does kcat/Km approach the diffusion-controlled rate of enzyme association with substrate?) f. If a kinetic measurement was made using 2 nanomoles of enzyme per mL and saturating amounts of substrate, what would Vmax equal? g. Again, using 2 nanomoles of enzyme per mL of reaction mixture, what concentration of substrate would give v = 0.75 Vmax? h. If a kinetic measurement was made using 4 nanomoles of enzyme per mL and saturating amounts of substrate, what would Vmax equal? What would Km equal under these conditions?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. Assessing the-Metabolic Consequences of Life Without Enzymes The incredible catalytic power of enzymes can perhaps best be appreciated by imagining how challenging life would be without just one of the thousands of enzymes in the human body. For example, consider life without fnnctose-1,6-btsphosphatase, an enzyme in the gluconeogenesis pathway in Liver and kidneys (see Chapter 22). which helps product new glucose from the food we eat: Fructose-1.6-blsphosphate + H2O Fmrlose-6-P + Pi The human brain requires glucose as its only energy source, and the typical brain consumes about 120 g (or 480 kilocalories) of glucose dally. Ordinarily, two pieces of sausage pizza could provide more than enough potential glucose to feed the brain for a day. According to a national fast-food chain, two pieces of sausage pizza provide 1340 kilocalories. 48% of which is from fat. Fats cannot be converted to glucose in gluconeogenesis, so that leaves 697 kilocalories potentially available for glucose synthesis. The first-order rate constant for the hydrolysis of fructose-l.6-bispliosphate in the absence of enzyme is 2 10-20 /sec. Calculate how long it would take to provide enough glucose for one day of brain activity from two pieces of sausage pizza without the enzyme. The following graphs show the temperature and pH dependencies of four enzymes, A, Β, X, and Y. Problems 12 through IS refer to these graphs.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. Characterizing a Covalent Enzyme Inhibitor Tosyl-L-phenylalanme cfaloromethyl ketone (TPCK) specifically inhibits chymotrypsin by covalently labeling His57 Propose a mechanism for the inactivation reaction, indicating the structure of the produce(s). State why this inhibitor is specific tor cJiymotrypsin. Propose a reagent based on the structure of TPCK that might be an effective inhibitor of trypsin.arrow_forward
- Answers 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 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. Graphing the Results from Kinetics Experiments with Enzyme Inhibitors The following kinetic data were obtained for an enzyme in the absence of any inhibitor (1), and in the presence of two different inhibitors (2) and (3) at 5 mM concentration. Assume [ET] is the same in each experiment. Graph these data as Lineweaver-Burk plots and use your graph to find answers to a. and b. a. Determine Vmax and Km for the enzyme. b. Determine the type of inhibition and the K1 for each inhibitor.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. Understanding Stereochemical Transformations of Amino Acids Absolute configurations of the amino acids are referenced to D- and L-glyceraldehyde on the basis of chemical transformations that can convert the molecule of interest to either of these reference isomeric structures. In such reactions, the stereochemical consequences for the asymmetric centers must be understood for each reaction step. Propose a sequence of reactions that would demonstrate that L(-)-serine is stereochemically related to l(- )-glyceraldehyde.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. 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. Exploring the Action of Phospholipase A2 As you read Suction 8.7, you might have noticed that phospholipase A2, the enzyme found in rattlesnake venom, is also the enzyme that produces essential and beneficial lipid signals in most organisms, lix. plain the differing actions of phospholipase At in these processes.arrow_forward
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