Enzymes (a protein) are catalysts found in organisms. Its efficiency of catalysing a reaction is due to its capacity to lower the activation energy of the reaction. The enzyme ptyalin used for food digestion is present in ___________________?

Related Mcqs:

1. The rate expression for a heterogeneous catalytic reaction is given by, – rA = K.KA PA(1 + KA.PA + KR.PR), where K is surface reaction rate constant and KA and KR are absorption equilibrium constants of A and R respectively. If KR PR >> (1 + KA PA), the apparent activation energy EA is equal to (given E is the activation energy for the reaction and ΔHR and ΔHA are the activation energies of adsorption of R and A) ?

   A. E
   B. E + ΔHA
   C. E + ΔHA – ΔHR)
   D. ΔHA + ΔHR

2. The catalytic activity of enzymes is due to their capacity to lower the ______________ energy?

   A. Activation
   B. Potential
   C. Kinetic
   D. None of these

3. A chemical reaction occurs, when the energy of the reacting molecules is ________________ the activation energy of reaction?

   A. Less than
   B. Equal to
   C. More than
   D. Equal to or more than

4. A chemical reaction occurs when the energy of the reacting molecules is __________________ the activation energy of the reaction?

   A. Less than
   B. Equal to
   C. More than
   D. Equal to or more than

5. The minimum energy required to allow a chemical reaction to proceed is termed as the ‘threshold energy ‘. Chemical reactions with low activation energy are ________________?

   A. Always irreversible
   B. Insensitive to temperature changes
   C. Mostly irreversible
   D. Highly temperature sensitive

6. In a reaction, the threshold energy is equal to (where, A = activation energy N = normal energy of reactants) ?

   A. A
   B. N
   C. A + N
   D. A – N

7. Rate constant for a first order reaction does not depend upon reaction time, extent of reaction and the initial concentration of reactants; but it is a function of reaction temperature. In a chemical reaction, the time required to reduce the concentration of reactant from 100 gm moles/litre to 50 gm moles/litre is same as that required to reduce it from 2 gm moles/litre to 1 gm mole/litre in the same volume. Then the order of this reaction is ?

   A. 0
   B. 1
   C. 2
   D. 3

8. Overall rate of reaction in a heterogeneous catalytic reaction depends upon the mass and energy transfer from the fluid to solid surface and its rate of reaction is usually ________________ the concentration of catalyst, if it does not entail a chain mechanism?

   A. Proportional to
   B. Independent of
   C. Inversely proportional to
   D. Proportional to the square of

9. Higher free energy of activation of a chemical reaction (at a given temperature) implies ____________________?

   A. Slower rate of reaction
   B. Higher rate of reaction
   C. Higher equilibrium conversion
   D. Both B. and C.

10. When the reaction occurs in the diffusion controlled region, the apparent activation energy as measured is only _______________ the true value?

    A. Twice
    B. Half
    C. Equal
    D. None of these