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

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
by

1 Answer

Answer :

a. Competitive Inhibition
by

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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) Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme. (c) Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate. (d) Non-competitive inhibitors often bind to the enzyme irreversibly.

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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 of succinic dehydrogenase by malonate. (c) A non-competitive inhibitor binds the enzyme at a site distinct from that which binds the substrate. (d) Malonate is a competitive inhibitor of succinic dehydrogenase.

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Last Answer : Answer : A

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Feedback inhibition of enzyme is influenced by (A) Enzyme (B) External factors (C) End product (D) Substrate

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Feedback inhibition of enzyme action is affected by (A) Enzyme (B) Substrate (C) End products (D) None of these

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Competitive inhibition can be relieved by raising the (A) Enzyme concentration (B) Substrate concentration (C) Inhibitor concentration (D) None of these

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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

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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

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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

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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 decreases the Km of the enzyme for the substrate. (c) A competitive inhibitor reacts reversibly with the enzyme to form an enzyme-inhibitor complex. (d) In competitive inhibition, the inhibitor molecule is not chemically changed by the enzyme.

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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

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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

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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 acetylcholine B. Regeneration time of the phosphorylated enzyme is longer than the turnover time of the enzyme molecules C. Phosphorylation results in rapid degradation of enzyme molecules D. They are neither metabolized nor excreted from the body

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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 acetylcholine B. Regeneration time of the phosphorylated enzyme is longer than the turnover time of the enzyme molecules C. Phosphorylation results in rapid degradation of enzyme molecules D. They are neither metabolized nor excreted from the body

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Which factor is responsible for inhibition of enzymatic process during feedback? (a) Substrate (b) Enzymes (c) End product (d) Temperature

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Do non competitive inhibitors bind to the active site?

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Last Answer : Feel Free to Answer

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

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Where Do the Enzyme and substrate Bind?

Description : Where Do the Enzyme and substrate Bind?

Last Answer : What is the answer ?

The inhibition of succinate dehydrogenase by malonate by (A) Competitive inhibition (B) Non-competitive inhibition (C) Uncompetitive inhibition (D) Feedback inhibition

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Allosteric enzymes regulate the formation of products by (A) Feedback inhibition (B) Non-competitive inhibition (C) Competitive inhibition (D) Repression-derepression

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Allosteric inhibition is also known as (A) Competitive inhibition (B) Non-competitive inhibition (C) Feedback inhibition (D) None of these

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What does the noncompetitive inhibitor bind to?

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An allosteric enzyme is generally inhibited by (A) Initial substrate of the pathway (B) Substrate analogues (C) Product of the reaction catalysed by allosteric enzyme (D) Product of the pathway

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‘Lock’ and ‘Key’ model of enzyme action proposed by Fisher implies that (A) The active site is flexible and adjusts to substrate (B) The active site requires removal of PO4 group (C) The active site is complementary in shape to that of the substrate (D) Substrates change conformation prior to active site interaction

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Fischer’s ‘lock and key’ model of the enzyme action implies that (A) The active site is complementary in shape to that of substance only after interaction. (B) The active site is complementary in shape to that of substance (C) Substrates change conformation prior to active site interaction (D) The active site is flexible and adjusts to substrate

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The acquisition energy by glucose fermentation requires A.substrate-level phosphorylation B.electron transport of electrons from NADH C.long-chain fatty acid oxidation D.the enzyme formic-hydrogen lyase

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Most of the energy in aerobic respiration of glucose is captured by A- substrate-level phosphorylation B- electron transport of electrons from NADH C- long-chain fatty acid oxidation D- the enzyme formic-hydrogen lyase

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Feedback term refers to (A) Effect of substrate on rate of enzymatic reaction (B) Effect of end product on rate reaction (C) Effect of enzyme concentration on rate of reaction (D) Effect of external compound on rate of reaction

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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 : 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

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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

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

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In non competitive enzyme activity inhibition, inhibitor (A) Increases Km (B) Decreases Km (C) Does not effect Km (D) Increases Km

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Last Answer : Answer : C

In competitive enzyme activity inhibition (A) Apparent Km is decreased (B) Apparent Km is increased (C) Vmax is increased (D) Vmax is decreased

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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

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

Which inactivates an enzyme by occupying its active site? (A) Competitive inhibitor (B) Allosteric inhibitor (C) Non-competitive inhibitor (D) All of these

Description : Which inactivates an enzyme by occupying its active site? (A) Competitive inhibitor (B) Allosteric inhibitor (C) Non-competitive inhibitor (D) All of these

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What will happen if the secretion of parietal cells of gastric glands is blocked with an inhibitor? (a) In the absence of HCl secretion, inactive pepsinogen is not converted into the active enzyme pepsin. (b) Enterokinase will not be released from the duodenal mucosa and so trypsinogen is not converted to trypsin. (c) Gastric juice will be deficient in chymosin. (d) Gastric juice will be deficient in pepsinogen.

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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

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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

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