Lock and Key Theory

Q.

What is meant by denaturation of enzyme?

Q. Which of the following is true regarding the active site of an enzyme?

1. The active site is formed by the foldings and crevices in the tertiary structure
2. The substrate binds to the active site
3. The enzyme catalyzes a reaction through its active site
4. All the above

Q.

An organic substance that binds to the enzyme and is essential for its activity, is called-

1. holoenzyme

2. apoenzyme

3. isoenzyme

4. coenzyme

Q. An enzyme may be rendered inoperative by

1. adding apoenzyme
2. removing byproducts as soon as they are formed
3. doubling its concentration
4. blocking its active site

Q. Explain hexokinase induced fit .

Q. The ‘‘lock and key’’ model of enzyme action illustrates that a particular enzyme molecule

1. interacts with a specific type of substrate molecule
2. forms a permanent enzyme-substrate complex
3. reacts at identical rates under all conditions
4. may be destroyed and resynthesised several times

Q.

If we assume that the 'lock and key model' of the enzyme-substrate interaction is correct, which of these conditions is absolutely true?

1. The enzyme can bind to substrates of only one shape

2. Substrates can change the shape of the active site

3. There is a competition between different substrates to bind to the active site

4. There is a change in the shape of the active site after binding to the substrate

Q. An enzyme may be rendered inoperative by

1. adding apoenzyme
2. doubling its concentration
3. blocking its active site
4. removing byproducts as soon as they are formed

Q. Which of the following is true regarding the active site of an enzyme?

1. The active site is formed by the foldings and crevices in the tertiary structure
2. The substrate binds to the active site
3. The enzyme catalyzes a reaction through its active site
4. All the above

Q. A T${}_4$ bacteriophage has a gene for the enzyme, lysozyme. The function of this enzyme is to digest the bacterial

1. Cell wall
2. Cell membrane
3. Golgi
4. Plasmid

Q. Arrange the steps of catalytic action of an enzyme in order and select the correct option.
I. The enzyme release the products of the reaction and the enzyme is free to bind to another substrate.
II. The active site of enzyme is in close proximity of the substrate and breaks the chemical bonds of the subtrate.
III. The binding of sustrate induces the enzyme to alter its shape fitting more tightly around the sustrate.
IV.The substrate binds to the active site of the enzyme.

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

Q. In a chemical reaction, the location on an enzyme in which the substrate binds to the enzyme is known as which of these?

1. Product
2. Allosteric site
3. Catalyst
4. Active site
5. Substrate

Q. All enzymes of the TCA cycle are located in the mitochondrial matrix except one, which is located in inner mitochondrial membrane in eukaryotes and in cytosol in prokaryotes. This enzyme is

1. Succinate dehydrogenase.
2. Lactate dehydrogenase.
3. Isocitrate dehydrogenase.
4. Malate dehydrogenase.

Q. Enzymes which are slightly different in molecular structure but can perform identical activity are

1. Holoenzymes
2. Apoenzymes
3. Isoenzymes
4. Coenzymes

Q. Which of the following is true regarding the active site of an enzyme?

1. The enzyme catalyzes a reaction through its active site
2. All the above
3. The substrate binds to the active site
4. The active site is formed by the foldings and crevices in the tertiary structure

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

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

Q. The trypsin enzyme is secreted by

1. Duodenum
2. Stomach
3. Pancreas
4. Liver

Q. Arrange the steps of catalytic action of an enzyme in right order and select the correct option.
(i) The enzyme releases the products of the reaction and the enzyme is free to bind to another substrate.
(ii) The active site of enzyme is in close proximity of the substrate and breaks the chemical bonds of the substrate.
(iii) The binding of substrate induces the enzyme to alter its shape fitting more tightly around the substrate.
(iv) The substrate binds to the active site of the enzyme fitting into the active site.

1. iii, ii, i, iv
2. iv, iii, ii, i
3. iv, ii, i, iii
4. ii, i, iv, iii

Q. What is the name given to that part of the enzyme where catalytic work is carried out ?

Q. When lactose is added to culture of Escherichia coli, its molecules get into the cell with the help of

1. Lactase
2. Permease
3. Transacetylase
4. Galactosidase

Q. Which of the following is the two major transporter of the malate-aspartate shuttle?

1. Malate- alpha-ketoglutarate transporter
2. Glutamate - aspartate transporter
3. Both A and B
4. Sodium-potassium transporter

Q. The cofactor present in the microbial enzyme catalase-peroxidase is:

1. Zn
2. NAD
3. NADP
4. Haem

Q. Which of the following is true regarding the active site of an enzyme?

1. The active site is formed by the foldings and crevices in the tertiary structure
2. The substrate binds to the active site
3. All the above
4. The enzyme catalyzes a reaction through its active site

Q. All of the following take place in lock and key model except

1. The substrate binds to the active site.
2. The enzyme lowers the activation energy of the reaction.
3. The enzyme is changed by the substrate.
4. The enzyme is altered by the reaction
5. The substrate is chemically changed by the enzyme.