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Biochemistry

Description: Biochemistry, Biotechnology
Number of Questions: 30
Created by:
Tags: Enzymes Chemical and Functional Nature of Enzymes
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Why is high temperature dangerous to a human?

  1. Because proteins are used up quickly.

  2. Because fats are oxidized.

  3. Because enzymes are denatured.

  4. Because BMR is lowered.

  5. Because carbohydrates are oxidized.

Show answer
Correct Option: C
Explanation:

At high temperature the enzymes get denatured in the body and their chemical reactivity ceases. That is  why it  is necessary to take immediate precaution, if there is rise in body temperature.

Why is heat used to sterilize nonliving objects in tissue culture?

  1. Proteins are denatured at temperature above 55oC.

  2. Proteins lose their tertiary structures due to break down of bonds.

  3. Both are correct.

  4. Proteins synthesis does not occur at high temperature.

  5. Both are incorrect.

Show answer
Correct Option: C
Explanation:

Heat is used to sterilize nonliving objects in tissue culture as the proteins are natured and their tertiary structures are lost at high temperature.

What does the term feedback refer to?

  1. Effect of substrate on the rate of enzymatic reaction.

  2. Effect of end product on the rate of reaction.

  3. Effect of enzyme concentration on the rate of reaction.

  4. Effect of external compound on the rate of reaction.

  5. Effect of cytoplasm on the rate of reaction.

Show answer
Correct Option: B
Explanation:

The effect of end product on the rate of reaction is referred as feedback mechanism.

Sometimes enzymes are named according to the source from which they are obtained. Name the enzyme obtained from pineapple.

  1. Bromelain

  2. Maltose

  3. Sucrose

  4. Pineallelase

  5. Papain

Show answer
Correct Option: A
Explanation:

The enzyme obtained from pineapple is called bromelain. Papain is obtained from papaya.

Which of the following is the best evidence for the Lock and Key theory of enzyme action?

  1. All isolated enzymes have been identified as proteins.

  2. Compounds similar in structure to substrate a molecule may inhibit the reaction.

  3. Enzymes speed up and determine the direction of a reaction.

  4. Enzymes are found only in cytoplasm of a cell.

  5. Enzymes are found only in the vacuoles of a cell.

Show answer
Correct Option: B
Explanation:

According to Lock and key Theory, the active site of an enzyme is static in nature. It has a specific geometric shape where in the substrate molecule fits. It is just like a key and its particular lock in which levers of key act like active site of the enzyme to open a particular lock (substrate).

What does the turn over number of an enzyme mean?

  1. Number of substrate molecules acted upon by one molecule of an enzyme per minute.

  2. Number of enzyme molecules acting on one molecule of substrate per minute.

  3. Number of molecules of end product produced by an enzyme in one minute.

  4. Number of substrate molecules acted upon by an enzyme per second.

  5. Number of enzyme molecules participating in the chemical reaction.

Show answer
Correct Option: A
Explanation:

Number of substrate molecules acted upon by one molecule of an enzyme per minute is called the turn over number of an enzyme.

The spoilage of food can be prevented by keeping it in cold storage. Which of the following could be the possible reason for this?

  1. Reduced respiration of bacteria.

  2. Reduced enzyme activity of bacteria.

  3. Reduced enzyme activity in substrate molecule.

  4. More availability of pure oxygen in cold storage.

  5. More availability of digestive enzymes in cold storage.

Show answer
Correct Option: B
Explanation:

Enzymatic activity reduces at extreme low or high temperatures. That is why it is advised to store the food at cold places so as to prevent it from bacterial attack.

Enzyme action depends on hydration of protoplasm. They come to almost a stop when hydration falls to _________.

  1. 10 - 20%

  2. 5 - 10%

  3. 2 - 5%

  4. 15 - 25%

  5. 30 - 35%

Show answer
Correct Option: A
Explanation:

The activity of enzymes depends upon the hydration of the protoplasm. Their activity stops when the hydration of protoplasm falls to 10-20%.

In a diluted starch solution, α-salivary amylases is added at pH 1.6 and kept at 35oC for half an hour and then iodine solution is added. What would be observed in the reaction?

  1. Orange coloured solution

  2. Black coloured solution

  3. Clear and colourless solution

  4. Reddish brown coloured solution

  5. Brick red colored solution

Show answer
Correct Option: B
Explanation:

Black colour appears if the iodine solution is added to starch solution.

What are the multiple molecular forms of an enzyme occurring in the same organism and having a similar substrate activity called?

  1. Isoenzymes

  2. Analogous enzymes

  3. Isomeric enzymes

  4. Pro enzymes

  5. Lysozymes

Show answer
Correct Option: C
Explanation:

The multiple molecular forms of an enzyme occurring in the same organism and having a similar substrate activity are called isomeric enzymes.

Which of the following enzymes does not obey Km kinetics?

  1. Allosteric enzymes

  2. Proenzymes

  3. Zymogens

  4. Exoenzymes

  5. Both 1 and 2

Show answer
Correct Option: A
Explanation:

The value of Km  (Michaelis-Menten constant) varies from 10-1 to 10-6 M but for allosteric enzymes, there is no constant Km value.

Isoenzymes are structural variants of the same enzyme. If LDH has 5 isomers in liver, α-amylase in wheat endosperm has how many isoenzymes?

  1. 16

  2. 5

  3. 3

  4. 1

  5. 7

Show answer
Correct Option: A
Explanation:

There are 16 isoenzymes present in the α-amylase in wheat endosperm.

Carbonic anhydrase enzyme has the maximum turn over number (36 million). The minimum turn over number for an enzyme is 30 per minute (0.5 per second). Identify the enzyme.

  1. DNA polymerase

  2. Lysozyme

  3. Penicillase

  4. Lactase dehydrogenase

  5. Proenzyme

Show answer
Correct Option: B
Explanation:

Lysozyme is a carbonic anhydrase enzyme. It has maximum turn over number.

Enzymes have high molecular weight and therefore, cannot move from cell to cell. Every cell synthesizes its own enzymes. Which of the following is responsible for the synthesis of enzymes in each cell?

  1. ribosomes

  2. m-RNA

  3. cytoplasm

  4. intrinsic proteins

  5. extrinsic proteins

Show answer
Correct Option: B
Explanation:

m-RNA is responsible for the synthesis  of enzymes,  which helps to speed the reaction.

An enzyme is a protein which differs from an inorganic catalyst in that is highly specific. This specificity of the enzyme is associated with the ___________.

  1. insoluble nature of the protein molecule

  2. high molecular weight of the protein molecule

  3. surface configuration of the protein molecule

  4. absence of metallic ions in the protein molecule

  5. soluble nature of the protein molecule

Show answer
Correct Option: C
Explanation:

The specificity of the enzyme is associated with the surface configuration of the protein molecule.

The monopoly of proteins to form enzymes is now not universal. Certain catalytic RNA (RNA enzymes) like Ribozyme discovered by RNAse- P (Ribonucleases P ) discovered by Altman are not proteins but act as catalysts. These RNA enzymes differ from protein enzymes in _______.

  1. that they catalyse only RNA molecules

  2. that they catalyse only nucleic acid molecules

  3. that they catalyse only phosphoprotein molecules

  4. both 2 and 3

  5. both 1 and 3

Show answer
Correct Option: A
Explanation:

RNA enzymes only  catalyse only RNA molecules whereas protein enzymes helps to catalyse nucleic acid molecules, phosphoprotein molecules,  etc.

Enzyme inhibition caused by a product of enzyme catalyzed reaction is ___________.

  1. competitive inhibition

  2. non competitive inhibition

  3. feedback inhibition

  4. metabolic antagonism

  5. allosteric inhibition

Show answer
Correct Option: A
Explanation:

Competitive inhibition is caused by blocking of active sites of enzyme by an inhibitor which closely resembles with that of the substrate but does not undergo any change.

What is the stoppage of an enzymatic (biological) reaction by the end product of reaction called?

  1. Feed back inhibition

  2. Negative inhibition

  3. End product inhibition

  4. Biocatalyst inhibition

  5. 1, 2 and 3 are correct

Show answer
Correct Option: E
Explanation:

The stoppage of an enzymatic (biological) reaction by the end product of reaction  is called feedback or negative,  or end product inhibition.

What are the compounds that denature the enzyme or cause non-specific inactivation of the active site called?

  1. Competitive inhibitors

  2. Non-competitive inhibitors

  3. Prosthetic groups

  4. Irreversible inhibitors

  5. Allosteric inhibitors

Show answer
Correct Option: D
Explanation:

Irreversible inhibitors denature the enzyme or cause non-specific inactivation of the active site.

Enzymes are able to accelerate a reaction because ___________.

  1. reacting substances are brought into highly specific relations with each other

  2. energy is added to the system

  3. molecules of the reactants are speeded up so that random encounters are more

  4. products of the reaction are removed simultaneously

  5. metallic ions are absent in the protein molecules

Show answer
Correct Option: A
Explanation:

Enzymes are able to accelerate a reaction because reacting substances are brought into highly specific relations with each other.

Which of the following enzymes convert glucose into ethyl alcohol/enzyme complex involved in alcohol fermentation?

  1. Invertase

  2. Zymase

  3. Diastrase

  4. Protease

  5. Decarboxylase

Show answer
Correct Option: B
Explanation:

Enzyme that converts glucose into ethyl alcohol/enzyme complex involved in alcohol fermentation is called zymase.

What is the phenomenon of change in an enzyme’s shape following binding of substrate called?

  1. Active site

  2. Induced fit

  3. Crystallography

  4. Allosteric inhibition

  5. Competitive inhibition

Show answer
Correct Option: B
Explanation:

The phenomenon of change in an enzyme’s shape following binding of substrate called induced fit.

Sulpha drugs/sulphanilamide kill bacteria by inhibiting synthesis of which of the following?

  1. Para-aminobenzoic acid

  2. Folic acid

  3. Phenylalanine

  4. Methionin

  5. Terylene

Show answer
Correct Option: B
Explanation:

Sulpha drugs/ sulphanilamide inhibits the synthesis of folic acid,  which is an important constituent of bacteria.

Which among the following enzymes is defective in the genetic disorder called Albinism?

  1. Hexokinase

  2. Tyrosinase

  3. Phenylalanine hydroxylase

  4. Succinyl dehydrogenase

  5. Diastrase

Show answer
Correct Option: B
Explanation:

Albinism is a genetic disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of tyrosinase, a copper containing enzyme involved in the production of melanin.

One molecule of an enzyme is needed to convert 2 molecules of a substrate into products in 5 minutes. 10 molecules of the enzyme and 25 molecules of the substrate are mixed in a test tube. After 10 minutes, the test tube will be having ____________.

  1. products only

  2. products and 5 molecules of unreacted substrate

  3. products, enzymes and 5 molecules of unreacted substrate

  4. unreacted substrates

  5. products and enzymes

Show answer
Correct Option: E
Explanation:

Products and enzymes will be left in the test tube. As the substrate will be completely converted into products and the enzymes can be recovered as such at the end of the reaction.

Why are enzymes, vitamins and hormones classified into a category of biological chemicals?

  1. As they are exclusively synthesized in the body of a living organism

  2. As they help in regulating metabolism

  3. As they enhance oxidative metabolism

  4. As they are conjugated proteins

  5. As they prevent denaturation of proteins

Show answer
Correct Option: B
Explanation:

Enzymes, vitamins and hormones are classified into a category of biological chemicals as they help in regulating the metabolism of the living organism, and maintain the activities of their lives.

What does climacteric mean?

  1. Sudden increase in respiration during fruit ripening

  2. Sudden premature fall of all the fruits

  3. Shedding of flowers before anthesis

  4. Climax vegetation

  5. Sudden increase in the rate of photosynthesis

Show answer
Correct Option: A
Explanation:

Climacteric refers to the sudden increase in respiration during fruit ripening.

Which of the following statements regarding enzyme inhibition is correct?

  1. Competitive inhibition is seen when a substrate competes with an enzyme for binding to an inhibitor protein.

  2. Non-competitive inhibitors often bind to the enzyme irreversibly.

  3. Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate.

  4. Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme.

  5. Both 3 and 4 are correct.

Show answer
Correct Option: D
Explanation:

Competitive inhibition is caused by blocking of active sites of enzyme by an inhibitor that closely resembles with that of the substrate but does not undergo any change.  It is seen when the substrate and the inhibitor compete for the active site on the enzyme.

The catalytic efficiency of two different enzymes can be compared by the

  1. pH of optimum value

  2. formation of the product

  3. Km value

  4. molecular size of an enzyme

  5. Vmax value

Show answer
Correct Option: C
Explanation:

The value of Km  (Michaelis-Menten constant) varies from 10-1 to 10-6 M. The catalytic efficiency of two different enzymes can be compared by this value.

Which of the following enzymes can stimulate the germination of barley seeds?

  1. Protease

  2. Invertase

  3. α-amylase

  4. Lipase

  5. Dextrase

Show answer
Correct Option: C
Explanation:

α-amylase can be used to stimulate the germination of barley seeds.

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