Which of the following statements about enzymes is true?

  1. Enzymes do not alter the overall change in free energy for a reaction
  2. Enzymes are proteins whose three dimensional shape is key to their functions
  3. Enzymes speed up reactions by lowering activation energy
  4. Enzyme are highly specific for reactions
  5. An enzyme like any protein has the secondary and tertiary structure.
  6. The energy input needed to start a chemical reaction is called activation energy

(a) All are correct  (b) All except 5      (c) 5 and 6          (d) 2 and 4

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Activation energy:
(a) Is the difference in the average energy content of 'S' from that of its transition state
(b) Helps to change reactants into unstable transition state before they can be converted into products
(c) Is minimum energy required from outside to overcome the energy barrier of reactant or to start a reaction
(d) All are correct

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   I. Segment representing the energy of activation.

   II. Segment representing the amount of free energy released by the reaction.

   III. Transition state

   IV. Segment would be the same regardless of whether the reaction were uncatalysed or catalysed

Which one is correct?

 

I

II

III

IV

(a)

1

3

2

4

(b)

1

2

3

2

(c)

1

3

2

4

(d)

1

2

4

3

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Which one of the graphs shows the effect of pH on the velocity of a typical enzymatic reaction (V)?

1.     2.     3.      4.

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Which one of the graphs show the effect of temperature on the velocity of a typical enzymatic reaction?

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Which one of the following graphs show the relationship between the rate of an enzymatic activity and substrate conc.(S):

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Choose the correct statement(s):
(a) Km (Michaelis - Menten) constant is the substrate concentration at which the enzymatic reaction attains half of its maximum velocity (1/2 Vmax)
(b) At lower Km, higher the substrate affinity for enzyme
(c) Vmax is reached when all the active sites of an enzyme are saturated with substrate
(d) All are correct

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In competitive inhibition:

(a) Inhibitor resembles the substrate in molecular structure

(b) Competition between substrates and inhibitors to occupy active sites

(c) Binding the inhibitors to activities sites declines the enzyme action

(d) All are correct

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Amylase is an example of:

(a) Oxidoreductase                                      (b) Transferase

(c) Hydrolase                                              (d) Ligase

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A. Catalyses the transfer of a group (other than hydrogen).
B. Catalyses removal group from substrates by mechanism other than hydrolysis leaving double bond
C. Catalyzing the linking of 2 molecules by using energy into one molecule.
Identify the classes of enzymes for above functions:

 

A

B

C

(a)

Ligase

Lyase

Transferase

(b)

Transferase

Lyase

Ligase

(c)

Lyase

Ligase

Transferase

(d)

Transferase

Ligase

Lyase

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