Mechanism of Enzyme Action

Q.
I. Segment representing the energy of activation
II. Segment representing the amount of free energy released by the reaction
III. Transition state

Which one is correct?

1. 1-II, 2-I, 3-III
2. 1-I, 2-II, 3-III
3. 1-III, 2-II, 3-I
4. 1-I, 2-III, 3-II

Q. Which of the following factor(s) affect(s) enzyme activity?

1. Temperature
2. Concentration of substrate
3. Concentration of product
4. pH

Q. Transition state structure of the substrate formed during an enzymatic reaction is:

1. Permanent but unstable
2. Transient and unstable
3. Transient but stable
4. Permanent and stable

Q. Cyanide kills animals by inhibiting cytochrome oxidase (an enzyme of respiration) by binding irreversibly with copper. It does not bind with active sites. This is an example of

1. feedbackinhibition
2. all of the above
3. non competitive inhibition
4. competitive inhibition

Q.

What is a substrate?

Q.

Pick the wrong equation for the enzyme-substrate reaction

1. E+P ↔ EP

2. E+S --> ES

3. E+S --> ES --> EP --> E+P

4. E+P --> EP

Q. One molecule of an enzyme is able to catalyse conversion of two molecules of substrate into products in 5 minutes. Ten molecules of enzyme and 25 molecules of substrate are mixed in a test tube. At the end of 10 minutes the test tube will have ___.

1. Products only
2. Products and enzymes molecules
3. Products and 5 unreacted substrate molecules
4. Products, enzyme molecules and 5 molecules of substrate.

Q. If an enzyme solution is saturated with substrate, then the most effective way to obtain an even faster yield of the products would be to add

1. more of the enzyme
2. a non-competitive inhibitor
3. an allosteric inhibitor
4. more substrate

Q. Increasing the substrate concentration beyond a certain point does not increase the rate of reaction. Why?

1. Substrate and enzyme lose their affinity for each other with increasing substrate concentration
2. There are no free enzymes available to react with the increased number of substrates
3. With increasing substrate concentration, pH of the reaction medium changes
4. With increasing substrate concentration there is no free space available for the reaction to occur

Q. Transition state structure of the substrate formed during an enzymatic reaction is

1. transient and unstable
2. permanent but unstable
3. permanent and stable
4. transient but stable

Q. How many of the following are directly required in PCR?
Deoxyribonucleotides, buffer, E. coli, Taq DNA polymerase, primer, DNA probe, DNA cutting (restriction) enzymes, host cell

1. 5
2. 4
3. 7
4. 2

Q. The enzyme required for copying genetic information from one strand of DNA into RNA is

1. DNA dependent DNA polymerase
2. DNA dependent RNA polymerase
3. RNA dependent RNA polymerase
4. RNA dependent DNA polymerase

Q. Increasing the substrate concentration beyond a certain point does not increase the rate of reaction. Why?

1. Substrate and enzyme lose their affinity for each other with increasing substrate concentration
2. With increasing substrate concentration there is no free space available for the reaction to occur
3. With increasing substrate concentration, pH of the reaction medium changes
4. There are no free enzymes available to react with the increased number of substrates

Q. Which of the following representation shows the correct steps in catalytic reaction of an enzyme?

1. E + S $\to$ E + P
2. E + S $\to$ ES $\to$ E + P
3. E + S $\to$ EP $\to$ E + P
4. E + S $\to$ ES $\to$ EP $\to$ E + P

Q.

a) What process is represented by the image given above?
b) Which enzyme is used for this process?
c) Write the steps involved in this process sequentially. [1+1+1]

Q. Which of the following factor(s) affect(s) enzyme activity?

1. Temperature
2. Concentration of substrate
3. Concentration of product
4. pH

Q. (a) Identify steps A and B in a cycle of Polymerase Chain Reaction given below.

(b) State the specific characteristic feature of the enzyme in carrying step B. [3 marks]

Q. I. PCR requires prior knowledge of at least part of the sequence of the target DNA so that primers can be constructed.
II. The technique of PCR was developed by Alec Jeffreys.

1. Both I and II are true
2. I is true and II is false
3. I is false and II is true
4. Both I and II are false

Q. Enzyme can start a chemical reaction.

1. False
2. True

Q. Which of the following is the best evidence for the lock and key hypothesis of enzyme action?

1. All isolated enzymes have been identified as proteins
2. Enzymes determine the direction of a reaction
3. Enzymes are found in living organisms and speed up certain reactions
4. Compounds similar in structure to the substrate inhibit the reaction

Q.

What is a first-order effect?

Q.

What do HDAC inhibitors do?

Q. The removal of which of the following enzymes affects the synthesis of 5srRNA?

1. RNA polymerase I
2. RNA polymerase II
3. RNA polymerase III
4. Helicase

Q. What is the role of enzyme Taq polymerase in gene amplification ?

Q. In a chemical reaction, enzyme catalyse the reaction by

1. Increasing the activation energy.
2. Lowering the activation energy.
3. Decreasing the free energy change between reactants and products.
4. Increasing the free energy change between reactants and products.

Q. Which is the best evidence for lock and key theory (Template theory)?

1. Feedback inhibition
2. Competitive inhibition
3. Allosteric competition
4. Non-competitive inhibition

Q. If an enzyme solution is saturated with substrate, then the most effective way to obtain an even faster yield of the products would be to add

1. more of the enzyme
2. a non-competitive inhibitor
3. an allosteric inhibitor
4. more substrate

Q. Who coined the term 'enzyme' for the first time?

Q. Transition state structure of the substrate formed during an enzymatic reaction is

1. unstable
2. stable
3. depends on the substrate
4. depends on the product

Q. Which of the following factor(s) affect(s) enzyme activity?

1. Temperature
2. Concentration of substrate
3. Concentration of product
4. pH