BIOC2201 Lecture 19: Theme 4 Notes

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

Below you will derive an equation to express the velocity of an enzyine catalyzed reaction in the presence of a jst algebra... competitive inhibitor kinetic scheme for a single substrate enzyme catalyzed reaction in the presence of a competitive inhibitor e Just as in the absence of a competitive inhibitor, the rate (velocity) of product formation with a competitive Inhiblior present is (a) v-ker [ES] Mass balance. In the presence of substrate and competitive inhibitor, the enzyme can be in one of three forms (ill In blanks);: 同..[ ]+[]+[ ] Divide. Divide equation (a) by the mass balance equation: Equilibria: ES and El complexes have dissociation constants that can be expressed as (ill in blanks): c)K1'I (d)K,-I Rearrange equation (c) and (d) to solve for ES and El respectively (ill in blanks) (e) (ES I OlEIlI1 Substitute. Rewrite equation () with the terns ES and El substituted with the right hand side of (e) and (0) Factor & simplify,. Now, on the right hand side of equation (g), I have factored out the [EJ terms, so they cancel, o give (h) [S]/K Finally, the numerator and denominator on the right side of equation (h) can be multiplied by K, and factored to give a sin form of the velocity equation: