Enzyme Catalysis, Kinetics and Regulation - Enzymes and General Principles of Metabolism - Life Sciences Previous Year Questions

1

2007 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2007

K_m values of enzyme X for substrate S₁ and S₂ are 0.1 mM and 0.01 mM, respectively. This suggest that
(P) enzyme X has more affinity towards S₁
(Q) enzyme X has low affinity towards S₁
(R) enzyme X has more affinity towards S2
(S) enzyme X has low affinity towards S2

A

P, Q

B

R, S

C

Q, S

D

Q, R

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2

2007 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2007

What would happen if enzyme X is incubated with a mixture of 0.1 mM of S₁ and S₂ ?

A

Products P₁ and P₂ are produced at equal concentrations

B

Only product P₂ is produced

C

More P₂ and less P₁ are produced

D

More P₁ and less P₂ are produced

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3

2007 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2007

Which of the following statements are INCORRECT about enzyme-mediated reaction in presence of inhibitor?
P    Competitive inhibition causes rise in K_m value without altering V_max
Q    Noncompetitive inhibition causes decrease in V_max and rise in K_m
R    Uncompetitive inhibition causes decrease in V_max without altering K_m
S    Uncompetitive inhibition is rare and causes a decrease in both V_max and K_m

A

P, Q

B

Q, R

C

P, R

D

P, S

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4

2007 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2007

Identify the correct expression for noncompetitive and competitive inhibition.

	Slope	Intercept on ordinate
P	Km/Vmax (1+I/Ki)	1/Vmax (1+I/Ki)
Q	Km/Vmax (1+I/Ki)	1/Vmax
R	Km/Vmax	1/Vmax (1+I/Ki)
S	Km/Vmax	1/Vmax

A

P, S

B

R, S

C

P, Q

D

Q, R

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5

2008 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2008

The catalytic efficiency of an enzyme is represented by

A

V_max

B

K_M

C

k_cat

D

k_cat/K_M

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6

2008 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2008

Match the transition state or chemical entity of each enzyme that is responsible for their catalytic function

A

P-3, Q-2, R-4, S-1

B

P-2, Q-3, R-1, S-4

C

P-2, Q-1, R-3, S-4

D

P-4, Q-3, R-2, S-1

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7

2008 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2008

Match the items on the left with the inhibitors on the right

A

P-2, Q-3, R-1

B

P-3, Q-1, R-2

C

P-2, Q-1, R-4

D

P-1, Q-2, R-4

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8

2008 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2008

Evaluate the Michaelis constant for the following lipase catalyzed trans-esterification reaction for the production of biodiesel
\(\displaystyle \text{Vegetable oil} + \text{Lipase} \xrightleftharpoons[k_1]{k_3} \text{Oil-lipase complex} \xrightarrow{k_2} \text{Biodiesel} + \text{Glycerol}\)
where, k₃ = 3 x 10⁶ M^-1 s^-1; k_-1 = 4 x 10⁴ s^-1 and k₂ = 2 x 10⁴ s^-1.

A

4.2 x 10^-3 M

B

14.0 x 10^-4 M

C

6.4 x 10^-6 M

D

1.4 x 10^-4 M

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9

2008 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2008

The time required to convert 10% of the substrate will be approximately

A

16 min

B

24 min

C

32 min

D

8 min

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10

2008 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2008

The maximum possible conversion for the enzymatic reaction will be

A

100%

B

50%

C

25%

D

12.5%

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11

2009 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2009

Generally, the rate-limiting step of major metabolic pathways is a reaction

A

in which the availability of the substrate is limited.

B

catalyzed by an allosteric enzyme.

C

catalyzed by an enzyme with very low Km.

D

whose products are not readily consumed by the subsequent step of the pathway.

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12

2009 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2009

One unit of glucoamylase enzyme activity is defined as the amount of enzyme required to produce 1 \( \mu mol \) of glucose per min in a 4% solution of Lintner starch at pH 4.5 and \( 60 ^\circ C \). If in a reaction mixture with 1 ml of the crude enzyme preparation containing 8 mg protein and 9 ml of 4.44% starch, 0.6 \( \mu mol \) of glucose/ml-min is produced, what will be the specific activity of the crude enzyme preparation ?

Check answer

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13

2010 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2010

Lineweaver-Burk plot is a plot of

A

\(\frac{1}{v_0}\) vs \(\frac{1}{[S]}\)

B

\(v_0\) vs \([S]\)

C

\(v_0\) vs \(\frac{1}{[S]}\)

D

\(\frac{1}{v_0}\) vs \([S]\)

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14

2010 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2010

Match the parameters in Group 1 with the correct options in Group 2 Group 1: P. K_M, Q. k_cat/K_M, R. pK_a, S. K_I Group 2: 1. Catalytic efficiency of the enzyme, 2. Affinity of enzyme to the inhibitor, 3. Affinity of enzyme to the substrate, 4. Maximum buffering capacity

A

P-3, Q-1, R-2, S-4

B

P-3, Q-1, R-4, S-2

C

P-1, Q-2, R-4, S-3

D

P-1, Q-4, R-2, S-3

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15

2010 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2010

Enzymes catalyze biochemical reactions by

A

Sequestering the product(s)

B

Decreasing the ΔG of the reaction

C

Increasing the ΔG of the reaction

D

Stabilizing the transition state of the reaction.

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16

2011 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2011

In the following enzyme catalyzed reaction which follows Michaelis-Menten kinetics
\[ E + S \underset{k_{-1}}{\overset{k_1}{\rightleftharpoons}} ES \xrightarrow{k_2} E + P \]
K_m is equal to

A

k₋₁/(k₁.k₂)

B

(k₁ . k₂)/k₋₁

C

k₁/(k₂ + k₋₁)

D

(k₂ + k₋₁)/k₁

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17

2011 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2011

An enzyme has a K_m of 4.7 × 10⁻⁵ M and V_max is 22 micro moles per litre per min. The enzyme reaction is carried out at a substrate concentration of 2 × 10⁻⁴ M. The initial reaction velocity for this enzyme catalyzed reaction will be

A

6.5 micro moles per litre per min

B

17.8 micro moles per litre per min

C

13.0 micro moles per litre per min

D

8.9 micro moles per litre per min

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18

2012 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2012

Match the enzymes in Group I with their corresponding activity in Group II

A

P-2, Q-3, R-4, S-1

B

P-1, Q-2, R-3, S-4

C

P-4, Q-1, R-2, S-3

D

P-3, Q-2, R-4, S-1

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19

2012 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2012

The kinetics of an enzyme in the presence (+I) or absence (-I) of a reversible inhibitor is described in the following graph.
If concentration of the reversible inhibitor in +I experiment was equal to 3.0 × 10^-3 M, then the dissociation constant for the enzyme-inhibitor complex is

A

1 × 10^-3 M

B

2 × 10^-3 M

C

3 × 10^-3 M

D

4 × 10^-3 M

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20

2012 · Life Sciences · Enzymes and General Principles of Metabolism · Enzyme Catalysis, Kinetics and Regulation

Life Sciences (XL) 2012

10 micrograms of the enzyme carbonic anhydrase (molecular weight = 30,000 g/mole) removes 300 milligrams of carbon dioxide per minute from the cells. The turnover number of the enzyme is

A

20 min^-1

B

2 × 10⁷ min^-1

C

2 × 10¹⁰ min^-1

D

7.2 × 10¹⁰ min^-1

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