Description : What is it called when an enzyme is blocked at its active site so the normal substrate can't bind? a. Competitive Inhibition b. Feedback Inhibition c. Noncompetitive Inhibition d. Pathway Modulation
Last Answer : a. Competitive Inhibition
Description : Enzymes combine with a ___________at the___________ site to lower the activation energy. a. Substrate; Active b. Product; Noncompetitive c. Product; Active d. Coenzyme; Active
Last Answer : a. Substrate; Active
Description : Which one of the following statements regarding enzyme inhibition is correct? (a) Competitive inhibition is seen when a substrate competes with an enzyme for binding to an inhibitor protein. (b ... large amount of substrate. (d) Non-competitive inhibitors often bind to the enzyme irreversibly.
Last Answer : (b) Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme
Description : Select the option which is not correct with respect to enzyme action. (a) Substrate binds with enzyme at its active site. (b) Addition of lot of succinate does not reverse the inhibition ... from that which binds the substrate. (d) Malonate is a competitive inhibitor of succinic dehydrogenase.
Last Answer : (b) Addition of lot of succinate does not reverse the inhibition of succinic dehydrogenase by malonate.
Description : In reversible non-competitive enzyme activity inhibition (A) Vmax is increased (B) Km is increased (C) Km is decreased (D) Concentration of active enzyme is reduced
Last Answer : Answer : D
Description : The sulfa drugs work by _______ with PABA in making folic acid. a. Positive Feedback b. Negative Feedback c. Competitive Inhibition d. Allosteric Inhibition
Last Answer : c. Competitive Inhibition
Description : The ability of CTP to bind to aspartate carbamoyltransferase and shut down the synthesis of more A- enzyme induction B- enzyme repression C- feedback inhibition of enzyme activity D- none of these
Last Answer : feedback inhibition of enzyme activity
Description : A drug ‘R’ producing no response by itself causes the log dose-response curve of another drug ‘S’ to shift to the right in a parallel manner without decreasing the maximal response: Drug ‘R’ is a: A. Partial agonist B. Inverse agonist C. Competitive antagonist D. Noncompetitive antagonist
Last Answer : C. Competitive antagonist
Description : Enzyme inhibition caused by a substance resembling substrate molecule is (A) Competitive inhibition (B) Non-competitive inhibition (C) Feedback inhibition (D) Allosteric inhibition
Last Answer : Answer : A
Description : Which one of the following regulatory actions involves a reversible covalent modification of the enzyme? (A) Phosphorylation of ser-OH on the enzyme (B) Allosteric modulation (C) Competitive inhibition (D) Non-competitive inhibition
Description : In competitive inhibition of enzyme action (A) The apparent Km is decreased (B) The apparent Km is increased (C) Vmax is decreased (D) Apparent concentration of enzyme molecules decreased
Last Answer : Answer : B
Description : Which of the following regulatory reactions involves a reversible covalent modification of an enzyme? (A) Phosphorylation of serine OH on the enzyme (B) Allosteric modulation (C) Competitive inhibition (D) Non-competitive inhibition
Description : Competitive inhibition can be relieved by raising the (A) Enzyme concentration (B) Substrate concentration (C) Inhibitor concentration (D) None of these
Description : In competitive inhibition, the inhibitor (A) Competes with the enzyme (B) Irreversibly binds with the enzyme (C) Binds with the substrate (D) Competes with the substrate
Description : In non competitive enzyme activity inhibition, inhibitor (A) Increases Km (B) Decreases Km (C) Does not effect Km (D) Increases Km
Last Answer : Answer : C
Description : In competitive enzyme activity inhibition (A) Apparent Km is decreased (B) Apparent Km is increased (C) Vmax is increased (D) Vmax is decreased
Description : In competitive enzyme activity inhibition (A) The structure of inhibitor generally resembles that of the substrate (B) Inhibitor decreases apparent Km (C) Km remains unaffective (E) Inhibitor decreases Vmax without affecting Km
Description : In reversible non-competitive enzyme activity inhibition (A) Inhibitor bears structural resemblance to substrate (B) Inhibitor lowers the maximum velocity attainable with a given amount of enzyme (C) Km is increased (D) Km is decreased
Description : If curve X in the graph (below) represents no inhibition for the reaction of the enzyme with its substrates, the curve representing the competitive inhibition, of the same reaction is (A) A (B) B (C) C (D) D
Description : An example of competitive inhibition of an enzyme is the inhibition of a. Succinic dehydrogenase by malonic acid b. Cytochrome oxidase by cyanide c. Hexokinase by glucose-6-phosphate d. Carbonic anhydrase by carbon dioxide
Last Answer : Ans: A
Description : Which one of the following statements is incorrect? (a) The competitive inhibitor does not affect the rate of breakdown of the enzyme-substrate complex. (b) The presence of the competitive inhibitor ... . (d) In competitive inhibition, the inhibitor molecule is not chemically changed by the enzyme.
Last Answer : (b) The presence of the competitive inhibitor decreases the Km of the enzyme for the substrate
Description : Genes which are active all the time synthesizing substances needed by the cell are called a) Cellular luxury genes b) metabolic genes c) house keeping genes d) control genes
Last Answer : c) house keeping genes
Description : Which inactivates an enzyme by occupying its active site? (A) Competitive inhibitor (B) Allosteric inhibitor (C) Non-competitive inhibitor (D) All of these
Description : A substance unrelated to substrate but capable of reversibly changing activity of enzyme by binding to a site other than active site is called (a) Competitive inhibitor (b) Non-competitive inhibitor (c) Catalytic inhibitor (d) Allosteric modulator/inhibitor
Last Answer : Ans. ((d))
Description : Contrast and compare competitive inhibitors with noncompetitive inhibitors. Which can be overcome by the addition of more substrate?
Last Answer : Competitive inhibitors reduce the productivity of enzymes by blocking substrates from entering active sites. This inhibition is what can be overcome by the addition of more substrate. Noncompetitive ... active site will become less and less effective at helping convert substrate to product.
Description : The following is a competitive antagonist of GABA but a noncompetitive antagonist of diazepam: A. Picrotoxin B. Muscimol C. Flumazenil D. Bicuculline
Last Answer : D. Bicuculline
Description : A drug which does not produce any action by itself but decreases the slope of the log dose-response curve and suppresses the maximal response to another drug is a: A. Physiological antagonist B. Competitive antagonist C. Noncompetitive antagonist D. Partial agonist
Last Answer : C. Noncompetitive antagonist
Description : The following statement is not true of log dose-response curve: A. It is almost linear except at the ends B. It is a rectangular hyperbola C. It facilitates comparison of different agonists D. It can help in discriminating between competitive and noncompetitive antagonists
Last Answer : B. It is a rectangular hyperbola
Description : Choose the correct statement about allopurinol: A. It is a purine antimetabolite with antineoplastic activity B. It is a competitive inhibitor of xanthine oxidase C. It is inactive itself ... D. Both allopurinol as well as its metabolite alloxanthine are noncompetitive inhibitors of xanthine oxidase
Last Answer : B. It is a competitive inhibitor of xanthine oxidase
Description : The active form of enzyme is A- apoenzyme B- coenzyme C- holoenzyme D- none of these
Last Answer : holoenzyme
Description : In the metabolic pathway, ABCDE, discuss what effect molecule E would likely have on regulating the enzyme that catalyzes the reaction of A to B?
Last Answer : E is the product. If there is enough of molecule E to complete a chemical process, for example, the molecules (reactants) ABCDE will not be needed, and therefore an excess of E means less of ABCDE produced.
Description : A competitive inhibitor of an enzyme has which of the following properties? (A) It is frequently a feedback inhibitor (B) It becomes covalently attached to an enzyme (C) It decreases the Vmax (D) It interferes with substrate binding to the enzyme
Description : Methylxanthines exert the following action (s) at cellular/molecular level (a) Intracellular release of Ca2+ (b) Antagonism of adenosine (c) Inhibition of phosphodiesterase (d) All of the above
Last Answer : Ans: D
Description : Methylxanthines exert the following action(s) at cellular/molecular level: A. Intracellular release of Ca2+ B. Antagonism of adenosine C. Inhibition of phosphodiesterase D. All of the above
Last Answer : D. All of the above
Description : A sigmoidal plot of substrate concentration ([S]) verses reaction velocity (V) may indicate (A) Michaelis-Menten kinetics (B) Co-operative binding (C) Competitive inhibition (D) Non-competitive inhibition
Description : The metabolic actions of adrenaline include the following except: A. Glycogenolysis in liver and muscle B. Inhibition of neoglucogenesis in liver C. Lipolysis in adipose tissue D. Release of potassium from liver followed by its uptake
Last Answer : B. Inhibition of neoglucogenesis in liver
Description : There are two properties of the cell necessary to maintain nonequilibrium cellular composition; the first is selectivity and the second is energy conversion. Which of the following statement(s ... transported via secondary active transport include hydrogen ions, calcium, amino acids and glucose
Last Answer : Answer: c, d The selectivity of the plasma membrane, although impressive, cannot account for the nonequilibrium composition of living cells. A cell can be maintained in a nonequilibrium state only by ... to drive the transport of a second species such as protons, calcium, amino acids, or glucose
Description : The organophosphates produce irreversible inhibition of cholinesterase because: A. They bind to an allosteric site of the enzyme resulting in unfavourable conformation of esteratic site to bind ... degradation of enzyme molecules D. They are neither metabolized nor excreted from the body
Last Answer : B. Regeneration time of the phosphorylated enzyme is longer than the turnover time of the enzyme molecules
Description : Allosteric inhibition (A) Makes active site unifit for substrate (B) Controls excess formation and end product (C) Both (A) and (B) (D) None of these
Description : When antigens are attached to the surface of latex beads and then reacted with an appropriate antibody, a/an reaction occurs. a. Inhibition b. Agglutination c. Neutralization d. Precipitation
Last Answer : b. Agglutination
Description : Negative regulation of protein synthesis is accomplished by A- allosteric inhibition B- the binding of RNA polymerase to the promoter C- the binding of a repressor to the DNA D- the binding of a repressor to the RNA polymerase
Last Answer : the binding of a repressor to the DNA
Description : In non-competitive enzyme action (A) Vmax is increased (B) Apparent km is increased (C) Apparent km is decreased (D) Concentration of active enzyme molecule is reduced
Description : The most common mechanism of development of resistance to fluoroquinolones is: A. Chromosomal mutation altering affinity of target site B. Plasmid transfer C. Acquisition of drug destroying enzyme D. Acquisition of alternative metabolic pathway
Last Answer : A. Chromosomal mutation altering affinity of target site
Description : Antibiotics will not work against _____ diseases because they lack the structures and metabolic machinery with which antibiotics interfere. a. viral b. bacterial c. fungal d. protozoan
Last Answer : a. viral