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BCH 2333 Lecture Notes - Lecture 3: Fischer Projection, Rate Equation, Reaction Rate Constant

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18 Oct 2016

School

University of Ottawa

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Course

Professor

Matthew Lafreniere

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Document Summary

Uncatalyzed reaction as the [s]s increases the rate increases where v=k[a][b]. Typical rate law, rate constant k, order = sum of the exponents. Enzyme catalyzed reactions show a different rate law. 2 stages 1 where the change in concentration of substrate changes the rate and a second stage at higher substrate concentration where the rate does not change. Model to account for this 2 phase kinetic character. This makes an enzyme substrate complex like p-l complex we have already seen. The enzyme substrate complex converts substrate into product. Clearly in many cases 2 substrates or more are reacting and multiple products can be formed this is a simplified mechanism. Adding in additional substrates and chemical steps is possible. For example es goes to ep then releases p. Useful for modeling product inhibition where the product of the reaction slows the reaction rate down. Most common and simplest model for dealing with enzyme rates.

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Related Questions

33-To stabilize the transition state complex, which of the following must be lowered? A) Initial energy state B) Activation energy C) Net energy change D) The Vmax B) Final energy state 34- Which of the following statements about allosteric enzymes is CORRECT? A The binding of substrate to any active site affects the other active sites B The plot of initial velocity vs. substrate concentration is a straight line C The Keq of the reaction is increased when allosteric activator is bound D The enzymes contains only one polypeptide chain E Allosteric activators bind to all active sites equally 35. Which statement about the two different models proposed to explain enzyme specificity is CORRECT. a. The substrate changes shape when enzyme binds in the Lock and Key Model. b. The enzyme undergoes a covalent modification when bound to substrate in the Lock and Key Model. c. The active site of the enzyme alternates in conformation between opened and closed in the Induced Fit Model. d. The enzyme changes conformation after binding the substrate in the Induced Fit Model. eÂ·The product structure is altered after it has bound to the enzyme in the Induced Fit Model. 36. An enzymatic reaction proceeds with maximal velocity (Vmax) when A. the substrate concentration is equal to that of a competitive inhibitor. B. allosteric effectors are present. C. the enzyme substrate complex is maximal. D. the substrate concentration exceeds that of a noncompetitive inhibitor. E. all of the substrate is bound to the enzyme. 37. Which of the statements below are incorrect? A With all other factors that modify the rate of the enzyme catalyzed reaction remaining constant as we raise the temperature of an enzyme catalyzed reaction there is an initial increase of velocity with temperature. B. The rate of reaction increases with temperature because there is an increasing number of molecules with sufficient energy to pass over the energy barrier which we call the energy of activation C. Reaction rate increases with temperature until a maximum is reached, when the rate of the reaction will suddenly suddenly fall to zero because the enzyme will be denatured and therefore inactive. D. The reaction rate initially increases as temperature rises owing to increased kinetic energy of the reacting molecules E. Enzymes in crease reaction rates due to their ability to lower the energy barriers for reactions F. None of the above 38- Which of the following is true for the induced fit theory of enzyme action? A. The conformation of the substrate changes before binding to the enzyme. B. The active site changes shape during binding of the substrate C. The substrate fits into a preformed active site through a lock-and-key mechanism. D. Enzymes alternate between conformations where the active site is either open or closed. E. The substrate causes a cleft to form in the enzyme where it subsequently binds

An allosteric interaction between a ligand and a protein is one in which: 74. changes in Km are negligible, so Km can be treated as a constant. C. binding of a molecule to a binding site affects binding of additional molecules to the same site. binding of a molecule to a binding site affects binding properties of another site on the protein. binding of the ligand to the protein is covalent. multiple molecules of the same ligand can bind to the same binding site. A. D. VO Vmax. E. varying [S] has no effect on Vo. 78. The steady state assumption, as applied to B. enzyme kinetics, implies: Km = Ks. the enzyme is regulated the ES complex is formed and broken down at equivalent rates. the Km is equivalent to the cellular substrate concentration A. B. C. C. D. D. E. the mximum velocity occurs when two different ligands can bind to the same binding site. E. the enzyme is saturated. The following data were obtained in a study of an enzyme known to follow Michaelis-Menten kinetics: 79. 75. One of the enzymes involved in glycolysis aldolase, requires Zn2+ for catalysis. Under conditions of zinc deficiency, when the enzyme may lack zinc, it would be referred to as the: Substrate added vo COmol/min) (mmol/L) A. apoenzyme. B. coenzyme. C. holoenzyme. D. prosthetic group. E. substrate 0.8 217 325 488 647 76. 1,000 The role of an enzyme in an enzyme- catalyzed reaction is to: bind a transition state intermediate, such that it cannot be converted back to substrate. ensure that all of the substrate is converted to product ensure that the product is more stable than the substrate. increase the rate at which substrate is converted into product. make the free-energy change for the reaction more favorable. A. The Km for this enzyme is approximately: B. C. D. E. A. 1 mM B. 1,000 mM. C. 2 mM D. 4 mM E. 6 mM 80. In competitive inhibition, an inhibitor: binds at several different sites on an enzyme. binds covalently to the enzyme. binds only to the ES complex. binds reversibly at the active site. lowers the characteristic Vmax of the enzyme A. B. C. D. E. 77. The benefit of measuring the initial rate of a reaction VO is that at the beginning of a reaction: A. [ES] can be measured accurately. B. changes in [S] are negligible, so [S can be treated as a constant