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MCQ ON THE ENZYMES
Question 1 : One of the enzymes involved in glycolysis, aldolase, requires Zn2+ for catalysis.
Under conditions of zinc deficiency, when the enzyme may lack zinc, it would be
referred to as the:
a. holoenzyme
b. prosthetic group
c. apoenzyme
d. coenzyme
Question 2: The concept of “induced fit” refers to the fact that:
a. when a substrate binds to an enzyme, the enzyme induces a loss of water
(desolvation) from the substrate.
b. substrate binding may induce a conformational change in the enzyme, which
then brings catalytic groups into proper orientation.
c. enzyme-substrate binding induces an increase in the reaction entropy, thereby
catalyzing the reaction.
d. enzyme specificity is induced by enzyme-substrate binding.
e. enzyme-substrate binding induces movement along the reaction coordinate to
the transition state.
Question 3 : A transition state analog:
a. resembles the transition-state structure of the normal enzyme-substrate
complex.
b. typically yields product more rapidly with an enzyme than the normal
substrate.
c. is less stable when binding to an enzyme than the normal substrate.
d. stabilizes the transition state for the normal enzyme-substrate complex.
e. resembles the active site of general acid-base enzymes.
Question 4 : Which of these statements about the composition of membranes is generally true?
a. The lipid composition of all membranes of eukaryotic cells is essentially the
same.
b. All biological membranes contain cholesterol.
c. Free fatty acids are major components of all membranes.
d. The inner and outer membranes of mitochondria have different protein
compositions.
Question 5 : The fluidity of a lipid bilayer will be increased by:
a. decreasing the number of unsaturated positions.
b. increasing the length of the alkyl chains.
c. increasing the temperature.
d. decreasing the temperature.
Question 6 : Which of the following statements about fatty acids is true?
a. Fatty acids with longer chain lengths have a higher melting point than fatty
acids with shorter chain lengths.
b. Saturated fatty acids have a lower melting point than unsaturated fatty acids.
c. Cis double bonds of unsaturated fatty acids cause tighter packing of
hydrophobic tails.
d. Double bonds in polyunsaturated fatty acids are almost always conjugated.
e. Fatty acids are found mostly as free acids.
Question 7 : Which of the following statements is not indicative of passive transport? Check
all that apply.
a. No energy is required.
b. ATP is required for transport.
c. Small organic molecules will diffuse based on molecular weight and solubility
in lipids.
d. Molecules are transported from low concentration to high concentration.
e. Molecules are transported from high concentration to low concentration.
Question 8 : Check all of the following that apply.
Enzyme catalysts:
a. shift the equilibrium of a reaction to favor products.
b. form asymmetric active sites due to their inherent chirality.
c. are sometimes permanently altered after releasing product.
d. often require prosthetic groups, which are transiently associated with a given
enzyme.
Question 9 : The conversion of NAD+ to NADH is an example of reduction because
a. the pyridine ring loses electrons (and a hydrogen).
b. the pyridine ring gains electrons (and a hydrogen).
c. the adenine ring loses electrons.
d. the adenine ring gains electrons.
Question 10 : Which of the following is not true of the reactions and enzymes in the glycolytic
pathway?
a. Triose phosphate isomerase is referred to as a “perfect enzyme” because
product is formed as soon as enzyme and substrate collide.
b. Phosphoglucose isomerase converts the glucose ring to a fructose ring.
c. Domains of phosphoglycerate kinase clamp down on the substrate so as to
exclude water from the reaction.
d. The reaction converting 2-phosphoglycerate to phosphoenolpyruvate is a
dehydration reaction.
e. Phosphofructokinase is stimulated by ATP and citrate.
Question 11 : Which of the following statements about glycogen metabolism is/are false?
I. Release of epinephrine leads to increased glycogen breakdown.
II. cAMP is a second messenger that triggers an increase in glycogen
synthesis.
III. Insulin results in dephosphorylation and subsequent activation of
glycogen synthase.
IV. Glucagon promotes glycogen breakdown.
V. Glucose-6-phosphate is an allosteric inhibitor of phosphorylase.
a. II only
b. V only
c. III and IV
d. II and V
e. III and V
Question 12 : coenzyme ‘A’ was discovered by
a. F.Cole
b. F.Lipmann
c. Menten
d. Banting and Best
Question 13 : Papain acts both in
a. high and low temperature
b. acidic and alkaline medium
c. stomach and mouth
d. all above
Question 14 : One of the catalyst oxidation reductionreactions
a. oxidase
b. oxidoreductase
c. oxygenase
d. all above
Question 15 : The word enzyme coined by
a. Kunhe
b. Sumner
c. Paine
d. Berzelius
Question 16 : ……..is the best example of the allosteric protein
a. Haemoglobin
b. Pepsin
c.
Carboxypepdidase
d. Trypsin
Question 17 : Coenzyme is
a. always protein
b. often metal
c. always inorganic compound
d. often a vitamine
Question 18 : Enzymes generally have
a. Same pH and temperature optima
b. Same pH and different temperature opyima
c.
Different pH but same temperature optima
d. Different pH and temperature optima
Question 19 : The fastest acting enzyme in the biological kingdom is
a. lipase
b. amylase
c. carboxypeptidase
d. carbonic an hydrates
Question 20 : Enzymes are absent in
a. fungi
b. bacteria
c. viruses
d. algae