Enzymes and Activation Energy

Q.

What is the minimum amount of energy required to start a chemical reaction?

Q.

Why are enzymes called organic molecules?

Q.

Is activation energy negative or positive?

Q.

Do enzymes increase the rate of a reaction?

Q. Which of the following describes the given graph correctly?

1. Endothermic reaction with energy A in absence of enzyme and B in the presence of an enzyme
2. Exothermic reaction with energy A in absence of enzyme and B in the presence of an enzyme
3. Endothermic reaction with energy A in presence of enzyme and B in the absence of an enzyme
4. Exothermic reaction with energy A in presence of enzyme and B in the absence of an enzyme

Q.

What is the main function of enzymes?

Q.

The function of an enzyme is to

1. Cause chemical reactions that would not otherwise take place

2. Changes the rates of chemical reactions

3. Change the direction of reactions

4. Control the equilibrium points of reactions

Q.

Can the activation energy be negative?

Q. Active site is also called:

1. Active spot
2. Substrate site
3. Allosteric site
4. Inhibitory site

Q. Enzymes speed up biochemical reactions by:

1. Increasing the temperature of the reaction
2. Lowering the temperature of the reaction
3. Increasing the activation energy of the reaction
4. Lowering the activation energy of the reaction

Q. Which of the following is false with respect to activation energy?

1. Activation energy is required for only endothermic reactions
2. Activation energy is required for only exothermic reactions
3. The activation energy can be decreased by enzyme
4. Both a and b

Q. Active site is also called:

1. Active spot
2. Substrate site
3. Allosteric site
4. Inhibitory site

Q.

The figure given below shows three velocity-substrate concentration curves for an enzyme reaction. What do the curve a, b and c depict respectively

1. a = Enzyme with an allosteric modulator added,

   b = Normal enzyme activity

   c = competitive inhibition

2. a = Normal enzyme reaction

   b = Competitive inhibition

   c = Non-competitive inhibition

3. a = Enzyme with an allosteric stimulator

   b = competitive inhibition added

   c = normal enzyme reaction

4. a = Normal enzyme reaction

   b = Non-competitive inhibitor added

   c = Allosteric inhibitor added.

Q. The role of an enzyme in a reaction is to

1. increase potential energy
2. increase activation energy
3. decrease activation energy
4. both a and b depending on the substrate

Q.

Which of these statements best explains the method by which enzymes catalyze a chemical reaction?

1. They bind to the substrate and reduce the activation energy of the reaction

2. They reduce the energy of the product thereby enabling the formation of the product

3. The speed increases due to the increase in heat during the ES complex formation

4. The reaction is catalyzed by free energy change