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
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
Question 2
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
Question 3
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
Question 4
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
Question 5
Reduction is the
A. loss of proton
B. gain of electron
C. loss of electron
D. gain of protons
Question 6
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
Question 7
An exergonic reaction is one that
A. requires energy to proceed
B. releases energy for work
C. gives off much heat
D. looses energy
Question 8
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
Question 9
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
Question 10
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
Question 11
In the reaction, C6H12O6+ 6O2 → 6CO2 + 6H2O + energy, which component is being oxidized?
A. C6H12O6
B. O2
C. CO2
D. H2O
Question 12
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
Question 13
In the reaction, C6H12O6 + 6O2 → 6CO2 + 6H2O + energy, which component is being reduced?
A. O2
B. CO2
C. H2O
D. Energy
Question 14
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
Question 15
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
Question 16
A substrate binds to its enzyme at a location called the __________ site.
A. coenzyme
B. substrate
C. active
D. polypeptide
Question 17
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
Question 18
Adenosine triphosphate is a type of
A. fatty acid
B. amino acid
C. nucleotide
D. steroid
Question 19
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
Question 20
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
Question 21
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
Question 22
Oxidation is the
A. loss of proton
B. gain of electron
C. loss of electron
D. gain of protons
Question 23
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
Question 24
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
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
Question 26
______________ 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
Question 27
4*107: Catalase :: 25: ___________
A. Protease
B. Amylase
C. Glucose isomerase
D. Creatinine kinase
Question 28
A low Km value points out a low affinity of an enzyme towards its substrate.
A. True
B. False
Question 29
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
Question 30
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
Question 31
Miachelis Menten model is also referred to as “rapid equilibrium model”.
A. True
B. False
Question 32
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
Question 33
What is the ratio of V0/Vmax when [S] = 10Km?
A. 1/2
B. 10/11
C. 4/5
D. 5/6
Question 34
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
Question 35
Which of the following is termed as catalytic efficiency?
A. Kcat
B. Km
C. Kcat/Km
D. Vmax
Question 36
Which of these is referred to as Kcat?
A. Miachelis Menten constant
B. Catalytic efficiency
C. Substrate concentration
D. Turn over number