Enzymes and Activation Energy

Q.

How do enzymes speed up reactions?

Q.

Is protein synthesis, endergonic or exergonic?

Q. The diagram illustrates energy changes in an enzyme controlled reaction. Which of the following represents the lowering of the activation energy?

1. X
2. Y
3. Z
4. Z-Y

Q. Enzymes speed up biochemical reactions by

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

Q.

Are enzymes reusable?

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

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

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

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

Q. How many molecules of ATP and NADPH are used to from one molecule of glucose through $C_3$ pathway?

1. 18, 12
2. 36, 24
3. 3, 2
4. 6, 4

Q.

Can a enzyme slow down a reaction?

Q. Active site is also called:

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

Q. Why enzymes are called biocatalyst?

Q. Which among the following is the fastest acting enzyme?

1. amylase
2. carbonic anhydrase
3. lipase
4. peptidase

Q. What is an enzyme?

1. A form of yeast
2. A substance broken down in metabolism
3. A chemical compound that helps in metabolism
4. A special chemical found within the nucleus

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

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

Q. The diagram illustrates energy changes in an enzyme controlled reaction. Which of the following represents the lowering of the activation energy?

1. Y
2. Z
3. X
4. Z-Y

Q.

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

1. They induce changes in the chemical state of the substrate leading to increase in the speed of the reaction

2. The reaction is catalyzed by free energy change

3. They bind to the substrate and the complex reduces the activation energy

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

Q. Choose the correct statement(s) for enzyme.

1. The structure of enzyme is complex.
2. Enzyme is very sensitive to pH and temperature.
3. Enzyme is very specific to its substrate.
4. Enzyme cannot be regulated.

Q.

What is the other name for biological catalysts?

Q. The location on the enzyme where the substrate binds to initiate a chemical reaction is called .

1. initiation site
2. reaction site
3. active site
4. binding site

Q.

Activation energy is required for

1. Exothermal reactions

2. Endothermal reactions

3. Enzyme mediated reactions

4. Starting all biochemical reactions

Q.

Mention one role of zinc in cells.

Q. Energy required for start of a chemical reaction is

1. Activation energy
2. Entropy
3. Potential energy
4. Kinetic energy

Q. Amino acids are building blocks of

1. Carbohydrates
2. Nucleic acids
3. Lipids
4. Proteins

Q. The diagram illustrates energy changes in an enzyme controlled reaction.


Which of the following represents the lowering of the activation energy?

1. X
2. Y
3. Z
4. Z - Y

Q. Explain aminoacylation of tRNA.

Q. Which among the following is the fastest acting enzyme?

1. Lipase
2. Amylase
3. Peptidase
4. Carbonic anhydrase

Q. Enzymes catalyse the conversion of a substrate into product by ___

1. increasing the activation energy
2. decreasing activation energy
3. getting consumed in the chemical reaction
4. reacting with the substrate to form products

Q. The tertiary structure of the proteins containing the amino acid cysteine is achieved through

1. Hydrogen bonds
2. Disulfide bonds and covalent bonds
3. Vander Waal's force
4. Ionic bonds
5. Covalent bonds only

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. 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