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Enzyme Reaction MCQ Questions & Answers

Enzyme Reaction MCQs : This section focuses on the "Enzyme Reaction". These Multiple Choice Questions (MCQs) should be practiced to improve the Enzyme Reaction skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.




Question 1

A low Km value points out a low affinity of an enzyme towards its substrate.

A. True
B. False

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Question 2

Which of the following is the best evidence for the lock and key theory of enzyme action?

A. Compounds similar in structure to the substrate inhibit enzyme activity
B. Enzymes are found in living organisms and speed up certain reactions
C. Enzymes speed up reactions by definite amounts
D. Enzymes determine the direction of a reaction

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Question 3

In the reaction, C6H12O6 + 6O2 → 6CO2 + 6H2O + energy, which component is being reduced?

A. O2
B. CO2
C. H2O
D. Energy

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Question 4

Oxidation is the

A. loss of proton
B. gain of electron
C. loss of electron
D. gain of protons

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Question 5

A substrate binds to its enzyme at a location called the __________ site.

A. coenzyme
B. substrate
C. active
D. polypeptide

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Question 6

Reduction is the

A. loss of proton
B. gain of electron
C. loss of electron
D. gain of protons

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Question 7

An enzyme that is always produced, regardless of the presence of substrates or the end products, is called

A. a constitutive enzyme
B. an isoenzyme
C. a repressible enzyme
D. an allosteric enzyme

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Question 8

Miachelis Menten model is also referred to as “rapid equilibrium model”.

A. True
B. False

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Question 9

The ability of FADH to be oxidized is __________ than the ability of FAD to be oxidized.

A. greater
B. lesser
C. approximately equal
D. half

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Question 10

If the free energy change (ΔG) in a reaction is a negative value, it indicates that the

A. reaction releases energy
B. reaction absorbs energy
C. reaction is in negative direction
D. reaction is in positive direction

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Question 11

The ability of CTP to bind to aspartate carbamoyltransferase and shut down the synthesis of more CTP is an example of

A. enzyme induction
B. enzyme repression
C. feedback inhibition of enzyme activity
D. None of these

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Question 12

Hydrogen and oxygen release enormous amounts of energy when they react. Yet, hydrogen and oxygen can be mixed together in a balloon and nothing will happen. Why?

A. Competitive inhibitors are blocking the reaction from occurring in the active site
B. There must be contaminating elements in the balloon that prohibit the reaction from occurring
C. The energy of activation to form the transition-state complex is too high to allow the reaction to occur without assistance
D. All of the above

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Question 13

An enzyme with a Km of 5mM has a reaction rate of 100 mmol/min at substrate concentration of 0.25 mmol. What is the maximum reaction rate that this enzyme can achieve when its saturated with substrate?

A. 2100
B. 1500
C. 1900
D. 9000

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Question 14

What is the ratio of V0/Vmax when [S] = 10Km?

A. 1/2
B. 10/11
C. 4/5
D. 5/6

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Question 15

______________ is defined as an enzyme molecule’s efficiency to convert maximum substrate molecules into product per unit time.

A. Catalytic efficiency
B. Miachelis Menten constant
C. Turn over number
D. Vmax

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Question 16

In the reaction, C6H12O6+ 6O2 → 6CO2 + 6H2O + energy, which component is being oxidized?

A. C6H12O6
B. O2
C. CO2
D. H2O

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Question 17

If the Keq for an enzymatic reaction is greater than 1, the reaction

A. will be endergonic
B. can not occur without the input of energy
C. both (a) and (b)
D. none of these

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Question 18

Given an enzyme with Km of 0.25mM, at what substrate concentration will the velocity of the enzyme reach 1/2 of the Vmax? (Vmax = 100 mmol/s)

A. 0.5 mM
B. 0.25 mM
C. 0.75 mM
D. 25 mM

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Question 19

An exergonic reaction is one that

A. requires energy to proceed
B. releases energy for work
C. gives off much heat
D. looses energy

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Question 20

The equation which is based on reciprocal form of Miachelis Menten equation at constant [Et] level is referred to as ______________

A. Eadie-Hofstee plot equation
B. Eisenthal and Cornish and Bowden plot equation
C. Lineweaver Burk equation
D. Hanes plot equation

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Question 21

An endergonic reaction is one that

A. requires energy in order to proceed
B. releases energy for work
C. gives off much heat
D. looses energy

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Question 22

4*107: Catalase :: 25: ___________

A. Protease
B. Amylase
C. Glucose isomerase
D. Creatinine kinase

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Question 23

The affinity of an enzyme for its substrate, when the enzyme has a Km of 0.50 M will be __________ than the affinity of an enzyme for its substrate when the enzyme has a Km of 0.05 M.

A. greater
B. lesser
C. approximately equal
D. half

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Question 24

The fact that β-oxidation of fatty acids, occurs in the mitochondria whereas fatty acid synthesis occurs in the cytoplasmic matrix, is an example of regulation of enzymatic activity by the __________ mechanism.

A. compartmentation
B. induction
C. competitive inhibition
D. repression

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Question 25

___________ is defined as the enzyme’s binding efficiency with its appropriate substrate through optimized multiple non-covalent interactions.

A. Km
B. Kcat
C. Catalytic efficiency
D. Vmax

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Question 26

The ability of Vibrio fischeri to convert chemical energy directly into radiant energy in bioluminescence is an example of __________ at work.

A. Shelford's law of tolerance
B. Leibig's law of the minimum
C. the first law of thermodynamics
D. the third law of thermodynamics

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Question 27

Which of the following is termed as catalytic efficiency?

A. Kcat
B. Km
C. Kcat/Km
D. Vmax

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Question 28

About 7.3 kcal/mole are released when

A. glucose is converted to CO2 and H2O
B. NAD+ is reduced to NADH
C. ATP hydrolysis is coupled to sucrose synthesis
D. the terminal phosphate bond of ATP is broken by hydrolysis

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Question 29

Denaturation of an enzyme refers to the

A. improper arrangement of the enzyme in a metabolic pathway
B. loss of the enzymes proper shape
C. formation of the enzymes proper shape
D. formation of a new isozyme for that enzyme

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Question 30

Anthranilate synthase, the first enzyme of tryptophan biosynthesis after the branch point shows feedback inhibition and repression due to

A. L-tryptophan
B. D-L-tryptophan hydantoin
C. L-serine
D. pyruvate

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Question 31

Which of these is referred to as Kcat?

A. Miachelis Menten constant
B. Catalytic efficiency
C. Substrate concentration
D. Turn over number

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Question 32

The ability of a competitive inhibitor to bind to an active site in an allosterically controlled enzyme is __________ than the ability of a non-competitive inhibitor to bind to an active site in the same allosterically controlled enzyme.

A. greater
B. lesser
C. approximately equal
D. half

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Question 33

Which of the following is based on rearrangement of Lineweaver Burk plot equation by multiplication of [So] factor?

A. Hanes plot equation
B. Eadie-Hofstee plot equation
C. Miachelis Menten equation
D. Eisenthal and Cornish and Bowden plot equation

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Question 34

To a living organism, which of the following has the greatest amount of available energy per molecule?

A. ATP
B. ADP
C. AMP
D. H2O

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Question 35

If the Keq for an enzymatic reaction is greater than 1, the reaction

A. will be endergonic
B. can not occur without the input of energy
C. Both A and B
D. None of these

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Question 36

Adenosine triphosphate is a type of

A. fatty acid
B. amino acid
C. nucleotide
D. steroid

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