CHEM102 Lecture Notes - Lecture 7: Enzyme

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. e·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

B. C. Mixed tive 8. The panereas is protected from digestion by trypsin (a proteolytic enzyme that it produces) because: A. B. C. D. Trypsin works only on denatured proteins Trypsin is specific for plant proteins Trypsin works only at the surface of membranes Trypsin is not activated until it is proteolytically modified 9. The active site of an enzyme is the region that A. binds allosteric regulators of the enzyme. B. is involved in the catalytic reaction of the enzyme C. binds noncompetitive inhibitors of the enzyme D. is inhibited by the presence of a coenzyme or a cofactor 10. According to the induced fit hypochesis of enzyme catalysis,which of the following is corect? A. The binding of the substrate depends on the shape of the active site B. Some enzymes change their structure when activators bind to the enzyme C. A competitive inhibitor can outcompete the substrate for the active site D. The binding of the substrate changes the shape of the enzyme's active site 11. Increasing the substrate concentration in an enzymatic reaction could overcome which of the following? A. denaturization of the enzyme B. allosteric inhibition C competitive inhibition D. saturation of the enzyme activity 12. Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n) A. competitive inhibitor of the enzyme B. noncompetitive inhibitor of the enzyme C. allosteric activator of the enzyme. D cofactor necessary for enzyme activity 13. Some of the drugs used to treat HIV patients are competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately, the high mutation rate of HIV means that the virus rapidly acquires mutations with amino acid changes that make them resistant to these competitive inhibitors. Where in the reverse transcriptase enzyme would such amino acid changes most likely occur in drug-resistant viruses? A. in or near the active site B. at an allosteric site Cat a cofactor binding site D. in regions of the protein that determine packaging into the virus capsid the fever is not controlled? When you have a severe fever, what grave consequence may occur if A. destruction of your enzymes' primary structure B. removal of amine groups from your proteins C. change in the tertiary structure of your enzymes D removal of the amino acids in active sites of your enzymes 14.