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

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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‘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

Description : 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 ( ... complementary in shape to that of the substrate (D) Substrates change conformation prior to active site interaction

Last Answer : Answer : C

Study of drug-receptor interaction has now shown that: A. Maximal response occurs only when all receptors are occupied by the drug B. Drugs exert an ‘all or none’ action on a receptor C. Receptor and drugs acting on it have rigid complementary ‘lock and key’ structural features D. Properties of ‘affinity’ and ‘intrinsic activity’ are independently variable

Description : Study of drug-receptor interaction has now shown that: A. Maximal response occurs only when all receptors are occupied by the drug B. Drugs exert an all or none' action on a ... lock and key' structural features D. Properties of affinity' and intrinsic activity' are independently variable

Last Answer : D. Properties of ‘affinity’ and ‘intrinsic activity’ are independently variable

Study of drug-receptor interaction has now shown that: A. Maximal response occurs only when all receptors are occupied by the drug B. Drugs exert an ‘all or none’ action on a receptor C. Receptor and drugs acting on it have rigid complementary ‘lock and key’ structural features D. Properties of ‘affinity’ and ‘intrinsic activity’ are independently variable

Description : Study of drug-receptor interaction has now shown that: A. Maximal response occurs only when all receptors are occupied by the drug B. Drugs exert an all or none' action on a ... lock and key' structural features D. Properties of affinity' and intrinsic activity' are independently variable

Last Answer : D. Properties of ‘affinity’ and ‘intrinsic activity’ are independently variable

The hypothesis to explain enzyme– substrate complex formation: (A) Lock and key model (B) Induced fit theory (C) Proenzyme theory (D) Both (A) and (B)

Description : The hypothesis to explain enzyme– substrate complex formation: (A) Lock and key model (B) Induced fit theory (C) Proenzyme theory (D) Both (A) and (B)

Last Answer : Answer : C

Template/lock and key theory of enzyme action is supported by (A) Enzymes speed up reaction (B) Enzymes occur in living beings and speed up certain reactions (C) Enzymes determine the direction of reaction (D) Compounds similar to substrate inhibit enzyme activity

Description : Template/lock and key theory of enzyme action is supported by (A) Enzymes speed up reaction (B) Enzymes occur in living beings and speed up certain reactions (C) Enzymes determine the direction of reaction (D) Compounds similar to substrate inhibit enzyme activity

Last Answer : Answer : D

An allosteric enzyme influences the enzyme activity by (A) Competiting for the catalytic site with the substrate (B) Changing the specificity of the enzyme for the substrate (C) Changing the conformation of the enzyme by binding to a site other than catalytic site (D) Changing the nature of the products formed

Description : An allosteric enzyme influences the enzyme activity by (A) Competiting for the catalytic site with the substrate (B) Changing the specificity of the enzyme for the substrate (C) Changing the conformation ... binding to a site other than catalytic site (D) Changing the nature of the products formed

Last Answer : Answer : C

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

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))

How an enzyme attaches to a substrate using the lock and key hypothesis?

Description : How an enzyme attaches to a substrate using the lock and key hypothesis?

Last Answer : What is the answer ?

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.

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.

In enzyme kinetics Km implies (A) The substrate concentration that gives one half Vmax (B) The dissocation constant for the enzyme substrate comples (C) Concentration of enzyme (D) Half of the substrate concentration required to achieve Vmax

Description : In enzyme kinetics Km implies (A) The substrate concentration that gives one half Vmax (B) The dissocation constant for the enzyme substrate comples (C) Concentration of enzyme (D) Half of the substrate concentration required to achieve Vmax

Last Answer : Answer : A

Key and lock hypothesis of enzyme action was given by (A) Fischer (B) Koshland (C) Buchner (D) Kuhne

Description : Key and lock hypothesis of enzyme action was given by (A) Fischer (B) Koshland (C) Buchner (D) Kuhne

Last Answer : Answer : A

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.

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

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

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

The shape of an enzyme and consequently its activity can be reversibly altered from moment to moment by (A) Heat (B) Amino acid substrate (C) Allosteric subunits (D) Sulfur substitutions

Description : The shape of an enzyme and consequently its activity can be reversibly altered from moment to moment by (A) Heat (B) Amino acid substrate (C) Allosteric subunits (D) Sulfur substitutions

Last Answer : Answer : C

In enzyme kinetics Vmax reflects (A) The amount of an active enzyme (B) Substrate concentration (C) Half the substrate concentration (D) Enzyme substrate complex

Description : In enzyme kinetics Vmax reflects (A) The amount of an active enzyme (B) Substrate concentration (C) Half the substrate concentration (D) Enzyme substrate complex

Last Answer : Answer : A

Why do we compare enzymes and substrate to a lock and key?

Description : Why do we compare enzymes and substrate to a lock and key?

Last Answer : What is the answer ?

Lock and Key mechanism of enzyme action? -Biology

Description : Lock and Key mechanism of enzyme action? -Biology

Last Answer : answer:

Enzyme inhibition caused by a substance resembling substrate molecule is (A) Competitive inhibition (B) Non-competitive inhibition (C) Feedback inhibition (D) Allosteric inhibition

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

Which one of the following is the correct mathcing of the site of action on the given substrate, the enzyme acting upon it and the end producrt?

Description : Which one of the following is the correct mathcing of the site of action on the given substrate, the enzyme acting upon it and the end producrt?

Last Answer : Which one of the following is the correct mathcing of the site of action on the given substrate, ... ( prop "Amylas")(rarr)` Disaccharie (Maltose)

Which of the following is the correct matchin of the site of action on the given substrate, the enzyme acting state upon it and the end product

Description : Which of the following is the correct matchin of the site of action on the given substrate, the enzyme acting state upon it and the end product

Last Answer : Which of the following is the correct matchin of the site of action on the given substrate, the ... alpha`-amylase `rarr` Disac- charide (Maltose)

Which one of the following is the correct matching of the site of action on the given substrate, the enzyme acting upon it and the end product? (a) Small intestine : Proteins Pepsin  →  Amino acids (b) Stomach : Fats Lipase  →  Micelles (c) Duodenum : Triglycerides Trypsin  →  Monoglycerides (d) Small intestine : Starch α-Amylase  →  Disaccharide (maltose)

Description : Which one of the following is the correct matching of the site of action on the given substrate, the enzyme acting upon it and the end product? (a) Small intestine : Proteins Pepsin  →  ... Trypsin  →  Monoglycerides (d) Small intestine : Starch α-Amylase  →  Disaccharide (maltose)

Last Answer : (d) Small intestine : Starch α-Amylase  →  Disaccharide

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

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

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

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

Which of the following statements about an enzyme exhibiting allosteric kinetics with cooperative interaction is false? (A) A plot of V-Vk [s] has a sigmaidal shape (B) An inhibitor may increase the apparent Km (C) Line weaver Bnrk plot is useful for determining Km and Vmax (D) Removal of allosteric inhibitor may result in hyperbolic V-S [s] plot

Description : Which of the following statements about an enzyme exhibiting allosteric kinetics with cooperative interaction is false? (A) A plot of V-Vk [s] has a sigmaidal shape (B) An inhibitor may increase the ... Km and Vmax (D) Removal of allosteric inhibitor may result in hyperbolic V-S [s] plot

Last Answer : Answer : D

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

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

Last Answer : Answer : C

Enzyme involved in joining together two substrates is (A) Glutamine synthetase (B) Aldolase (C) Gunaine deaminase (D) Arginase

Description : Enzyme involved in joining together two substrates is (A) Glutamine synthetase (B) Aldolase (C) Gunaine deaminase (D) Arginase

Last Answer : Answer : A

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

Last Answer : Answer : A

The phenomenon of inhibition of glycolysis by O2 is termed as (A) Red drop (B) Pasteur effect (C) Michaelis effect (D) Fischer’s effect

Description : The phenomenon of inhibition of glycolysis by O2 is termed as (A) Red drop (B) Pasteur effect (C) Michaelis effect (D) Fischer’s effect

Last Answer : Answer : B

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 : 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

Last Answer : Answer : C

Characteristic features of active site are (A) Flexible in nature (B) Site of binding (C) Acidic (D) Both (A) and (B)

Description : Characteristic features of active site are (A) Flexible in nature (B) Site of binding (C) Acidic (D) Both (A) and (B)

Last Answer : Answer : D

Which one of the following statements regarding a catalyst is not correct? A An enzyme is a catalyst that only binds certain substrates. B An enzyme is a protein that is a highly efficient catalyst for one or more chemical reactions in a living system. C Catalysts increase the rate of a reaction by altering the mechanism, thereby increasing the activation energy. D Catalysts do not alter the equilibrium constant for a chemical reaction.

Description : Which one of the following statements regarding a catalyst is not correct? A An enzyme is a catalyst that only binds certain substrates. B An enzyme is a protein that is a highly ... increasing the activation energy. D Catalysts do not alter the equilibrium constant for a chemical reaction.

Last Answer : C Catalysts increase the rate of a reaction by altering the mechanism, thereby increasing the activation energy.

What holds substrates in position during an enzyme catalyzed reaction?

Description : What holds substrates in position during an enzyme catalyzed reaction?

Last Answer : the acive site

Pick out the wrong statement. (A) Catalytic activity of enzyme catalysed reactions which is affected by temperature, pH value & chemical agents, is maximum at a temperature of about 45°C(B) Most of the enzyme catalysed reactions involve at least two substrates (C) Enzymes help in increasing the activation energy of the reaction (D) Equilibrium concentrations in enzyme catalysed reactions can be calculated by using the thermodynamic properties of substrates & prod

Description : Pick out the wrong statement. (A) Catalytic activity of enzyme catalysed reactions which is affected by temperature, pH value & chemical agents, is maximum at a temperature of about 45°C ... in enzyme catalysed reactions can be calculated by using the thermodynamic properties of substrates & prod

Last Answer : (C) Enzymes help in increasing the activation energy of the reaction

Enzymes combine with a ___________at the___________ site to lower the activation energy. a. Substrate; Active b. Product; Noncompetitive c. Product; Active d. Coenzyme; Active

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

The antiviral action of amantadine is exerted through: A. Interaction with the viral M2 protein B. Interaction with a virus directed thymidine kinase C. Inhibition of a viral protease enzyme D. Inhibition of viral RNA mediated DNA synthesi

Description : The antiviral action of amantadine is exerted through: A. Interaction with the viral M2 protein B. Interaction with a virus directed thymidine kinase C. Inhibition of a viral protease enzyme D. Inhibition of viral RNA mediated DNA synthesi

Last Answer : A. Interaction with the viral M2 protein

Substrate concentration at which an enzyme attains half its maximum velocity is (A) Threshold value (B) Michaelis-Menton constant (C) Concentration level (D) None of these

Description : Substrate concentration at which an enzyme attains half its maximum velocity is (A) Threshold value (B) Michaelis-Menton constant (C) Concentration level (D) None of these

Last Answer : Answer : B

Km value of enzyme is substrate concentration at (A) ½ Vmax (B) 2 Vmax (C) ½ Vmax (D) 4 Vmax

Description : Km value of enzyme is substrate concentration at (A) ½ Vmax (B) 2 Vmax (C) ½ Vmax (D) 4 Vmax

Last Answer : Answer : D

The ratio of enzyme to substrate molecules can be as low as (A) 1 : 100,000 (B) 1 : 500,000 (C) 1 : 10,000 (D) 1 : 1,000

Description : The ratio of enzyme to substrate molecules can be as low as (A) 1 : 100,000 (B) 1 : 500,000 (C) 1 : 10,000 (D) 1 : 1,000

Last Answer : Answer : A

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

Description : 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

Last Answer : Answer : B

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

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

Last Answer : Answer : C

Combination of apoenzyme and coenzyme produces (A) Prosthetic group (B) Holoenzyme (C) Enzyme substrate complex (D) Enzyme product complex

Description : Combination of apoenzyme and coenzyme produces (A) Prosthetic group (B) Holoenzyme (C) Enzyme substrate complex (D) Enzyme product complex

Last Answer : Answer : B

An enzyme promotes a chemical reaction by (A) Lowering the energy of activation (B) Causing the release of heat which acts as a primer (C) Increasing molecular motion (D) Changing the free energy difference between substrate and product

Description : An enzyme promotes a chemical reaction by (A) Lowering the energy of activation (B) Causing the release of heat which acts as a primer (C) Increasing molecular motion (D) Changing the free energy difference between substrate and product

Last Answer : Answer : A

The rate of an enzyme catalyzed reaction was measured using several substrate concentrations that were much lower than Km, the dependence of reaction velocity on substrate concentration can best be described as (A) Independent of enzyme concentration (B) A constant fraction of Vmax (C) Equal to Km (D) Proportional to the substrate concentration

Description : The rate of an enzyme catalyzed reaction was measured using several substrate concentrations that were much lower than Km, the dependence of reaction velocity on substrate concentration can best be ... constant fraction of Vmax (C) Equal to Km (D) Proportional to the substrate concentration

Last Answer : Answer : C

The Michaelis constant, Km is (A) Numerically equal to ½ Vmax (B) Dependent on the enzyme concentration (C) Independent of pH (D) Numerically equal to the substrate concentration that gives half maximal velocity

Description : The Michaelis constant, Km is (A) Numerically equal to ½ Vmax (B) Dependent on the enzyme concentration (C) Independent of pH (D) Numerically equal to the substrate concentration that gives half maximal velocity

Last Answer : Answer : D

Enzymes activity is controlled by (A) pH of the solution (B) Temperature (C) Concentration of the enzyme (D) Concentration of the substrate (E) All of these

Description : Enzymes activity is controlled by (A) pH of the solution (B) Temperature (C) Concentration of the enzyme (D) Concentration of the substrate (E) All of these

Last Answer : Answer : C

When [s] is equal to Km, which of the following conditions exist? (A) Half the enzyme molecules are bound to substrate (B) The velocity of the reaction is equal to Vmax (C) The velocity of the reaction is independent of substrate concentration (D) Enzyme is completely saturated with substrate

Description : When [s] is equal to Km, which of the following conditions exist? (A) Half the enzyme molecules are bound to substrate (B) The velocity of the reaction is equal to Vmax (C) The velocity of the reaction is independent of substrate concentration (D) Enzyme is completely saturated with substrate

Last Answer : Answer : A

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 : 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

Last Answer : Answer : D

The Michaehis-Menten hypothesis: (A) Postulates the formation of an enzyme substrate complex (B) Enables us to calculate the isoelectric point of an enzyme (C) States that the rate of a chemical reaction may be independent of substrate concentration (D) States that the reaction rate is proportional to substrate concentration

Description : The Michaehis-Menten hypothesis: (A) Postulates the formation of an enzyme substrate complex (B) Enables us to calculate the isoelectric point of an enzyme (C) States that the ... independent of substrate concentration (D) States that the reaction rate is proportional to substrate concentration

Last Answer : Answer : A

If a coenzyme is required in an enzyme reaction, the former usually has the function of (A) Acting as an acceptor for one of the cleavage products of the substrate (B) Enhancing the specificity of the apo enzyme (C) Increasing the number of receptor sites of the apo enzyme (D) Activating the substrate ENZYMES 167

Description : If a coenzyme is required in an enzyme reaction, the former usually has the function of (A) Acting as an acceptor for one of the cleavage products of the substrate (B) Enhancing the specificity ... C) Increasing the number of receptor sites of the apo enzyme (D) Activating the substrate ENZYMES 167

Last Answer : Answer : A

Velocity maximum for an enzyme at half the substrate concentration gives (A) The molecular weight of the enzyme (B) Km value (C) Isoelectric pH (D) Pk value

Description : Velocity maximum for an enzyme at half the substrate concentration gives (A) The molecular weight of the enzyme (B) Km value (C) Isoelectric pH (D) Pk value

Last Answer : Answer : B