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

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
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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

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

If the substrate concentration is much below the km of the enzyme, the velocity of the reaction is (A) Directly proportional to substrate concentration (B) Not affected by enzyme concentration (C) Nearly equal to Vmax (D) Inversely proportional to substrate concentration

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Last Answer : Answer : A

When the velocity of an enzymatic reaction equals Vmax, substrate concentration is (A) Half of Km (B) Equal to Km (C) Twice the Km (D) Far above the Km

Description : When the velocity of an enzymatic reaction equals Vmax, substrate concentration is (A) Half of Km (B) Equal to Km (C) Twice the Km (D) Far above the Km

Last Answer : Answer : D

From the L ineweaver-Burk p lot of Michaelis-Menten equation, Km and Vmax can be determined when V is the reaction velocity at substrate concentration S, the X-axis experimental data are expressed as (A) 1/V (B) V (C) 1/S (D) S

Description : From the L ineweaver-Burk p lot of Michaelis-Menten equation, Km and Vmax can be determined when V is the reaction velocity at substrate concentration S, the X-axis experimental data are expressed as (A) 1/V (B) V (C) 1/S (D) S

Last Answer : Answer : C

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

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

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

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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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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

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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

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

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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 : 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

Last Answer : Answer : C

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

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

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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

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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

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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

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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

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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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Last Answer : Answer : B

A competitive inhibitor of an enzyme (A) Increases Km without affecting Vmax (B) Decreases Km without affecting Vmax (C) Increases Vmax without affecting Km (D) Decreases both Vmax and Km

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Last Answer : Answer : A

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) Apparent Km is decreased (B) Apparent Km is increased (C) Vmax is increased (D) Vmax is decreased

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The kinetic effect of purely competitive inhibitor of an enzyme (A) Increases Km without affecting Vmax (B) Decreases Km without affecting Vmax (C) Increases Vmax without affecting Km (D) Decreases Vmax without affecting Km

Description : The kinetic effect of purely competitive inhibitor of an enzyme (A) Increases Km without affecting Vmax (B) Decreases Km without affecting Vmax (C) Increases Vmax without affecting Km (D) Decreases Vmax without affecting Km

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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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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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The presence of a non competitive inhibitor (A) Leads to both an increase in the Vmax of a reaction and an increase in Km (B) Leads to a decrease in the observed Vmax (C) Leads to a decrease in Km and Vmax (D) Leads to an increase in Km without affecting Vmax

Description : The presence of a non competitive inhibitor (A) Leads to both an increase in the Vmax of a reaction and an increase in Km (B) Leads to a decrease in the observed Vmax (C) Leads to a decrease in Km and Vmax (D) Leads to an increase in Km without affecting Vmax

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The curve given below shows enzymatic activity in relation to three conditions (pH, temperature and substrate concentration). What do the two axes (X and Y) represent? X-axis Y-axis (a) Enzymatic activity pH (b) Temperature Enzyme activity (c) Substrate Enzymatic concentration activity (d) Enzymatic activity Temperature

Description : The curve given below shows enzymatic activity in relation to three conditions (pH, temperature and substrate concentration). What do the two axes (X and Y) represent? X-axis ... (b) Temperature Enzyme activity (c) Substrate Enzymatic concentration activity (d) Enzymatic activity Temperature

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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

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

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In enzyme assays, all the following are kept constant except (A) Substrate concentration (B) Enzyme concentration (C) pH (D) Temperature

Description : In enzyme assays, all the following are kept constant except (A) Substrate concentration (B) Enzyme concentration (C) pH (D) Temperature

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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

Description : 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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Lineweaver – Burk double reciprocal plot is related to (A) Substrate concentration (B) Enzyme activity (C) Temperature (D) Both (A) and (B) ENZYMES 145

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Michaelis – Menten equation is used to explain the effect of substrate concentration on (A) Carbohydrate (B) Enzyme (C) Lipid (D) Protein

Description : Michaelis – Menten equation is used to explain the effect of substrate concentration on (A) Carbohydrate (B) Enzyme (C) Lipid (D) Protein

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All the following statements regarding calcium are correct except (A) It diffuses as a divalent cation (B) It freely diffuses across the endoplasmic reticulum of muscle cells (C) It can exist in the blood as ionic form and also protein bound (D) It is found in high concentration in bones

Description : All the following statements regarding calcium are correct except (A) It diffuses as a divalent cation (B) It freely diffuses across the endoplasmic reticulum of muscle cells (C) It can exist in the blood as ionic form and also protein bound (D) It is found in high concentration in bones

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The following abnormality in PRPP synthetase can cause primary gout: (A) High Vmax (B) Low Km (C) Resistance to allosteric inihbition. (D) All of these

Description : The following abnormality in PRPP synthetase can cause primary gout: (A) High Vmax (B) Low Km (C) Resistance to allosteric inihbition. (D) All of these

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In competitive inhibition which of the following kinetic effect is true ? (A) Decreases both Km and Vmax (B) Increases both Km and Vmax (C) Decreases Km without affecting Vmax (D) Increases Km without affecting Vmax

Description : In competitive inhibition which of the following kinetic effect is true ? (A) Decreases both Km and Vmax (B) Increases both Km and Vmax (C) Decreases Km without affecting Vmax (D) Increases Km without affecting Vmax

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Competitive inhibitors (A) Decrease the Km (B) Decrease the Vmax (C) Increase the Km (D) Increase the Vmax

Description : Competitive inhibitors (A) Decrease the Km (B) Decrease the Vmax (C) Increase the Km (D) Increase the Vmax

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In Lineweaver-Burk plot, the y-intercept represents (A) Vmax (B) Km (C) Km (D) 1/Km

Description : In Lineweaver-Burk plot, the y-intercept represents (A) Vmax (B) Km (C) Km (D) 1/Km

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If all the enzymes, intermediates and cofactors of the citric acid cycle as well as an excess of the starting substrate acetylCoA are present and functional in an organelle free solution at the appropriate pH, which of the following factors of the citric acid cycle would prove to be rate limiting? (A) Molecular oxygen (B) Half life of enzyme (C) Turnover of intermediates (D) Reduction of cofactors

Description : If all the enzymes, intermediates and cofactors of the citric acid cycle as well as an excess of the starting substrate acetylCoA are present and functional in an organelle free solution at the appropriate ... oxygen (B) Half life of enzyme (C) Turnover of intermediates (D) Reduction of cofactors

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Out of 24 mols of ATP formed in TCA cycle, 2 molecules of ATP can be formed at “substrate level” by which of the following reaction ? (A) Citric acid→ Isocitric acid (B) Isocitrate→ Oxaloacetate (C) Succinic acid→ Fumarate (D) Succinylcat→ Succinic acid

Description : Out of 24 mols of ATP formed in TCA cycle, 2 molecules of ATP can be formed at “substrate level” by which of the following reaction ? (A) Citric acid→ Isocitric acid (B) Isocitrate→ Oxaloacetate (C) Succinic acid→ Fumarate (D) Succinylcat→ Succinic acid

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Vmax of an enzyme may be affected by (A) pH (B) Temperature (C) Non-competitive inhibitors (D) All of these

Description : Vmax of an enzyme may be affected by (A) pH (B) Temperature (C) Non-competitive inhibitors (D) All of these

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Pick out the wrong statement. (A) α-particle emission from a radioactive element makes it electrically negative (B) β-particle emission from a radioactive element makes it electrically positive (C) A radioactive element having a half life period of 20 years will completely disintegrated in 40 years (D) The disintegration constant of a radioactive isotope is independent of pressure, temperature or concentration

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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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Induction of drug metabolizing enzymes involves: A. A conformational change in the enzyme protein to favour binding of substrate molecules B. Expression of enzyme molecules on the surface of hepatocytes C. Enhanced transport of substrate molecules into hepatocytes D. Increased synthesis of enzyme protein

Description : Induction of drug metabolizing enzymes involves: A. A conformational change in the enzyme protein to favour binding of substrate molecules B. Expression of enzyme molecules on the surface of ... C. Enhanced transport of substrate molecules into hepatocytes D. Increased synthesis of enzyme protein

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Induction of drug metabolizing enzymes involves: A. A conformational change in the enzyme protein to favour binding of substrate molecules B. Expression of enzyme molecules on the surface of hepatocytes C. Enhanced transport of substrate molecules into hepatocytes D. Increased synthesis of enzyme protein

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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

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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

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

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Last Answer : Answer : A

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

Description : 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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Example of enzyme specificity: (A) Stereo specificity (B) Reaction specificity (C) Substrate specificity(D) All of these

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A bio-catalyst produced by living cells which acts independent of the cell is called a/an (A) Substrate (B) Enzyme (C) Nutrient (D) None of these

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