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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5857_Библиотеки_им_академика_М_И_Перельмана.pdf
C. Cell maturation
D. All of the above
9. Which one of these vitamins has a role in oxidation
and reduction reactions?
A. Biotin B. Folate
C. Riboflavin D. Vitamin K
10. In the human body highest concentration of
ascorbic acid is found in:
A. Liver B. Adrenal cortex
C. Adrenal medulla D. Spleen
11. Which one of these vitamins has a role as an
antioxidant?
A. Biotin B. Folate
C. Niacin D. Vitamin E
12. Deciency of vitamin B1 can cause:
A. Rickets B. Beriberi
C. Nyctalopia D. Night blindness
13. Source(s) from which humans can fulfil the
deciency of vitamin A is/are:
A. Yellow fruits B. Liver
C. Fish D. All of these
14. Vitamin A was discovered in which year?
A. 1918 B. 1932
C. 1912 D. 1967
15. Which one of these vitamins has a role in oxidation
and reduction reactions?
A. Folate B. Niacin
C. Vitamin A D. Vitamin B6
16. Riboavin act as a coenzyme in a reaction which
is catalysed by one of the following enzymes:
A. Acy-CoA synthetase
B. Acyl-CoA dehydrogenase
C. Hydroxy acyl-CoA
D. Both A and C
17. Choose one wrong statement about ascorbic acid.
A. Strong reducing agent
B. Water-soluble vitamin
C. Has antioxidant activity
D. It can be synthesised in the body
18. With which of the following enzymes does
nicotinamide play a role of coenzyme:
A. Dehydrogenases B. Polymerases
C. Decarboxylases D. Hydrolases
19. What is the name of essential vitamin for fatty acid
synthesis?
A. Folate B. Biotin
C. Nicotinamide D. Vitamin E
20. The corrin ring system of B12 has:
A. Iron B. Sodium
C. Zinc D. Cobalt
21. Deciency of which one of these vitamins may
lead to hypochromic anaemia?
A. Vitamin B6 B. Vitamin B
12
C. Vitamin E D. Vitamin C
22. Biotin is a coenzyme of the enzyme:
A. Hydroxylase B. Decarboxylase
C. Carboxylase D. Oxidases
23. Which one of these vitamins is involved in
controlling cell differentiation and proliferation?
A. Vitamin A B. Vitamin C
C. Vitamin B6 D. Vitamin E
24. Tocopherols prevent the oxidation of:
A. Vitamin A B. Vitamin E
C. Vitamin C D. Vitamin B
12
25. Thiamine diphosphate is required for oxidative
decarboxylation of:
A. Triglycerides B. Keto acids
C. Fatty acids D. Amino acids
26. Deciency of which one of these vitamins is a
major cause of blindness?
A. Vitamin A B. Vitamin B
12
C. Niacin D. Vitamin K
27. FAD acts as a coenzyme for:
A. Succinate dehydrogenase
B. Glycerol-3-phosphate dehydrogenase
C. Sphingosine reductase
D. All of the above
28. Diseases such as rickets, scurvy and beriberi occur
because of lacking of:
A. Proteins B. Minerals
C. Lipids D. Vitamins
29. Name a substance that makes a vitamin
metabolically ineffective?
A. Antivitamin B. Antioxidants
C. Cyanocobalamin D. Riboflavinosis
30. Niacin is the chemical name of which vitamin?
A. Vitamin B3 B. Vitamin B
1
C. Vitamin B2 D. Vitamin C
31. _____________ serves as a precursor of a hormone.
A. Vitamin B2 B. Vitamin D
C. Vitamin A D. Vitamin E
32. NAD is required as a coenzyme in:
A. Citric acid cycle
B. HMP shunt
C. Reduction of fatty acids
D. All of the above
33. Niacin deciency can occur in:
A. Hartnup disease B. Phenylketonuria
C. Alkaptonuria D. None of these
34. The symptoms of retinol excess is/are:
A. Bone fragility B. Nausea
C. Weakness D. All of these
35. Glucose absorption increased by:
A. Vitamin A B. Thiamine
C. Ascorbic acid D. Niacin
Section 3 Biochemistry
409408
36. Folic acid contains:
A. Pteridine
B. p-Amino benzoic acid
C. Glutamic acid
D. All of the above
37. Which one of these vitamins is involved in
controlling cell differentiation and proliferation?
A. Vitamin B12 B. Vitamin D
C. Vitamin E D. Vitamin K
38. Rod cells possess a transmembrane protein which
is:
A. Adenylate cyclase B. Transducin
C. Rhodopsin D. B as well as C
39. Different types of vitamins are:
A. Fat-soluble B. Water-soluble
C. Both A and B D. None of the above
40. Retinoic acid is involved in the synthesis of:
A. Rhodopsin B. Iodopsin
C. Porphyrinopsin C. Glycoproteins
41. Deciency of which one of these vitamins may
lead to megaloblastic anaemia?
A. Vitamin B6 B. Vitamin B12
C. Vitamin D D. Vitamin K
42. A synthetic form of vitamin K is:
A. Menadione B. Farnoquinone
C. Phylloquinone D. None of these
43. Which one of these vitamins are required for DNA
synthesis?
A. Biotin B. Folate
C. Pantothenic acid D. Vitamin B6
44. The non-protein part of rhodopsin is:
A. Retinal B. Retinol
C. Carotene D. Repsin
45. The tocopherols prevent the oxidation of:
A. Vitamin A B. Vitamin D
C. Vitamin K D. Vitamin C
46. Which of the following vitamins is essential for
fatty acid synthesis?
A. Folate B. Pantothenic acid
C. Vitamin B6 D. Vitamin C
47. What is the major form of caloric storage in a
human body?
A. ATP B. Glycogen
C. Creatine phosphate D. Triacylglycerol
48. The deciency of vitamin B12 leads to:
A. Pernicious anaemia
B. Megaloblastic anaemia
C. Both A and B
D. None of the above
49. Calcitriol is:
Section 3 Biochemistry
A. 1-OH-cholecalciferol
B. 25-OH-cholecalciferol
C. 24, 25-diOH cholecalciferol
D. 1, 25-diOH cholecalciferol
50. Which of the following vitamins provides the
cofactor for the transfer of one-carbon units?
A. Folate B. Niacin
C. Riboflavin D. Vitamin B6
51. The extrinsic factor of Castle is:
A. Vitamin B
B. Glycoprotein
12
C. R-Proteins D. Sigma protein
52. Vitamin which has antioxidant properties is:
A. Vitamin A B. Vitamin C
C. Vitamin D D. Vitamin E
53. An intrinsic factor of Castle is:
A. Vitamin B12 B. Glycoprotein
C. R-Proteins D. Sigma protein
54. Out of the following which vitamin is involved
in blood coagulation?
A. Vitamin B6 B. Vitamin D
C. Vitamin E D. Vitamin K
55. Cholesterol is a precursor in the biogenesis of:
A. Vitamin A B. Vitamin D
C. Vitamin E D. None of these
56. Thymine is:
A. Water-Soluble vitamin
B. Fat-Soluble vitamin
C. Purine base
D. Pyrimidine base
57. A chemical name of vitamin K3 is:
A. Phylloquinone B. Menadione
C. Menaquinone D. Napthoquinone
58. This is a rich source for vitamin C:
A. Rice B. Milk
C. Egg D. Lemon
59. Vitamin _____________ is involved in calcium
homeostasis.
A. B
B. D
12
C. E D. A
60. Calcitriol is:
A. 1-hydroxy cholecalciferol
B. 25-hydroxy cholecalciferol
C. 24,25-dihydroxy cholecalciferol
D. 1,25-dihydroxy cholecalciferol
61. Fat-soluble vitamins have properties like:
A. Stored in liver
B. One or more propane units
C. Soluble in alcohol
D. All of the above
62. Deciency of which one of these vitamins may
lead to haemolytic anaemia?
A. Vitamin B12 B. Vitamin A
C. Vitamin D D. Vitamin E
63. The human species can biosynthesize:
A. Vitamin C B. Vitamin B
12
C. Thiamine D. Niacin
64. Which of the following vitamins provides the
cofactor for reduction reactions in fatty acid
synthesis?
A. Folate B. Niacin
C. Riboflavin D. Vitamin B6
65. Deciency of iron leads to:
A. Megaloblastic anaemia
B. Aplastic anaemia
C. Pernicious anaemia
D. Hypochromic microcytic anaemia
66. Which of the following vitamins provides the
cofactor for pyruvate dehydrogenase?
A. Folate B. Niacin
C. Thiamin D. Vitamin B6
67. Sulpha drugs are antimetabolites of:
A. Nicotinic acid B. Vitamin B
6
C. PABA D. Pantothenic acid
68. Symptoms of pellagra are:
A. Dermatitis and diarrhoea only
B. Dermatitis and dermentia only
C. Diarrhoea and dermentia only
D. Diarrhoea, dermatitis and dementia
69. Which of the following vitamins is essential for
gluconeogenesis from lactate?
A. Biotin B. Folate
C. Vitamin B6 D. Vitamin B12
70. Antisterility vitamin is:
A. Vitamin A B. Vitamin B
2
C. Vitamin E D. Vitamin C
71. Vitamin A is synthesized from:
A. γ-Carotene B. β-Carotene
C. α-Carotene D. All of these
72. Vitamin used in the treatment of homocystinuria
is:
A. B1 B. B
C. B12 D. B
5
6
73. Deficiency of which vitamin causes cerebral
haemorrhage?
A. Vitamin K B. Vitamin C
C. Vitamin A D. None of these
74. Which of the following vitamins provides the
cofactor for the transamination of amino acids?
A. Folate B. Niacin
C. Vitamin B6 D. Thiamin
75. Vitamin B6 deficiency may occur during
tuberculosis therapy with:
A. Rifampicin B. Sulpha drugs
C. Isoniazid D. Thamibutole
76. Vitamin K2 was originally isolated from:
A. Soybean B. Putrid fishmeal
C. Spinach D. Liver
ANSWER KEY
1. B 2. C 3. D 4. B 5. D 6. A 7. C 8. D 9. C 10. B 11. D 12. B 13. D 14. C
15. B 16. B 17. D 18. A 19. B 20. D 21. A 22. C 23. A 24. A 25. B 26. A 27. D 28. D
29. A 30. A 31. B 32. A 33. A 34. D 35. B 36. D 37. B 38. C 39. C 40. D 41. B 42. A
43. B 44. A 45. A 46. B 47. C 48. C 49. D 50. A 51. B 52. D 53. A 54. D 55. A 56. D
57. B 58. D 59. B 60. D 61. D 62. D 63. D 64. B 65. D 66. C 67. C 68. D 69. A 70. C
71. D 72. D 73. A 74. C 75. C 76. B
Section 3 Biochemistry
411410
6. Biological Oxidation and Reduction
Oxidation–Reduction Reactions
Oxidation–reduction (redox) reactions are chemical
reactions that involve the transfer of electrons between
two molecular species.
The two species can be organic or inorganic, and they
can exist in any phase of the environment (gas, liquid,
or solid).
In a complete redox reaction, one species begins in its
more reduced state and is oxidized (that is, loses one or
more electrons) during the reaction.
The other species, on the other hand, enters the reaction
in a more oxidized state and is reduced (accepts one or
more electrons).
Properties of enzymes
High catalytic power
A High degree of specificity for substrate
Accelerate chemical reactions tremendously.
Function in aqueous conditions at very mild temperature
and pH.
Nature of enzymes
Most of the enzymes are proteins (exception catalytic
RNA)
Denaturation or dissociation of enzyme subunits lead to
loss of catalytic function
The primary secondary tertiary and quaternary structure
of protein enzymes are essential to their catalytic activity
Enzymes have molecular weights ranging from about
12000 to > 1 million, some enzymes require a cofactor
Cofactor can be either inorganic science or can be a
complex of organic molecule called coenzyme
Prosthetic group A coenzyme or metal ion that is very
tightly or even covalently bound to the enzyme protein
Holoenzyme—complete catalytically active enzyme
together with its bound coenzyme and metal ions
Apoprotein/apoenzyme—only the protein part of the
holoenzyme
The function of coenzyme—carrier of transient functional
groups.
Enzyme classification
Oxidoreductase—transfer of electrons
Transferases—group transfer reactions
Hydrolases—hydrolysis reaction
Lyases—addition of groups to two double bonds or
formation of double bonds by elimination of groups
Isomerases—isomeric forms formed due to the transfer
of groups within the molecule itself
Section 3 Biochemistry
Ligases—formation of carbon–carbon, carbon-sulphur,
carbon–oxygen and carbon–nitrogen bonds.
Oxidative Phosphorylation
The process of oxidative phosphorylation is when
electrons are moved from reduced forms of nicotinamide
adenine dinucleotide (NADH) and flavin adenine
dinucleotide (FADH2) to molecular oxygen (O2) via a
series of electron transporters (i.e. the electron transport
chain).
Oxidative phosphorylation (OXPHOS) is an electron
transfer chain that is powered by substrate oxidation
and linked to ATP synthesis via an electrochemical transmembrane gradient.
7. Enzymes
Enzyme catalysis
An enzyme provides a specific environment within
which a given reaction can occur more rapidly.
Active site— catalytic site of an enzyme.
Substrate— a molecule found within the active site and
acted upon by the enzyme.
Ground state— the starting point of reaction.
Reaction intermediate- any species on the reaction
pathway that has a transient existence
Rate limiting step— step with the highest activation
energy.
A simple enzymatic reaction is represented like:
E = enzyme
S = substrate
P = product
ES = enzyme substrate complex
EP = enzyme product complex
An enzyme increases the reaction’s rate but does not
affect the equilibrium state of the reaction.
Activation energy—the difference of energy level
between the ground state and the transition state.
Higher activation energy corresponds to a slower
reaction.
Lower activation energy, a catalyst is added.
Catalyst in hence reaction rates by lowering the
activation energy.
Reaction intermediate—any species on the reaction
pathway that has a finite chemical lifetime.
Equilibrium constant (K’
at equilibrium is
K’
) for a S
eq
=
eq
P interconversion
(P)
(S)
From thermodynamics, the relationship between K’eq and
0
▲G’
can be described by the following expression
0
▲ G’
= –RT ln K’
s
where
R = Gas constant, 8.315 J/mol×K
T = Absolute temperature, 298 K (25ºC)
Binding energy: Energy derived from enzyme–substrate
interaction binding energy is a main source of free
energy which is used by enzymes to lower the activation
energy. The enzyme active site is not complementary to
the substrate but to the transition states through which
substrate pass as they are converted to products. Following
four physical and thermodynamics factors that contribute
to the activation energy and the mechanism used by
enzymes to counter them:
1. Reduction in entropy in the form of decreased freedom
of motion of two molecules in solution.
2. The solvation sells of hydrogen attached water that
surrounds and helps to stabilize various biomolecules
in aqueous solution.
3. The distortion of substance that must occur in various
directions.
4. The need for proper alignment of catalytic functional
group on the enzyme.
Mechanism of enzyme catalysis
1. General acid–base catalysis
z
Unstable charged intermediates generated in a
reaction immediately breakdown into constituent
reactants.
z
Such intermediates can be sterilized by the transfer
of protons to or from the substrate for intermediate
to form a species that breakdowns more really to
products.
z
Specific acid–base catalysis for non-enzymatic
reactions, proton transport is from water molecules
or weak proton acceptor or donors.
z
General acid–base catalysis: Proton transfer by other
classes of molecules.
2. Covalent catalysis: A transit covalent bond is formed
between the enzyme and the substrate in the presence
of a covalent catalyst the reaction becomes
Metal ion catalysis
Ionic interactions are formed between enzyme bound
metal and a substrate this helps to orion the substrate
for reaction or stabilize the charged reaction transition
state.
Metals can also mediate oxidation–reduction reactions
by reversible changes in the metal ion’s oxidation state.
Most enzymes used a combination of several catalytic
strategies to bring about catalysis. For example,
chymotrypsinogen uses both general acid–base catalysis
and covalent catalysis.
Enzyme kinetics
Reaction rates of enzyme catalysed reactions are studied
in enzyme kinetics and also study the rates which are
affected by changes in experimental conditions.
Saturation is an essential property of enzyme-catalysed
reactions: when the concentration of substrate increases
the rate increases and approaches a limit where there is
no dependence of rate of reaction on the concentration
of substances.
Leonor Michaelis and Maud Menten, scientist those
experiment with enzyme kinetics by using “modern”
ways like controlling the pH of the solution, etc.
Enzyme activity can be assayed in many ways either
disappearance of substrate or appearance of a product
Where:
S: Substrate
E: Enzyme
ES: Enzyme–substrate complex
P: Product
Michaelis-Menten model for enzyme kinetics
V = V
KM + [S]
V is the reaction rate (velocity) at a substrate concentration
[S]
V
is the maximum rate that can be observed in the
max
reaction—substrate is present in excess-enzyme can be
saturated (zero order reaction).
KM is the Michaelis constant— a constant that is related
to the affinity of the enzyme for the substrate, units are
in terms of concentration. It is a combination of rate
constants
KM = k2 + k–1
A simplest and easy model of enzyme kinetics.
This model gives justification that how an enzyme causes
increase in the kinetic rate of a reaction and why the rate
of a reaction depends on the amount of enzyme.
This model explains enzyme reversibly bind with
substrate and forms an ES complex that subsequently
yields product.
Km implies that 50% of the active sites on the enzymes
are filled. It is the measurement of the binding strength
between the substrate and the enzyme. Lower K
shows a greater affinity between the substrate and
enzymes.
V
—maximum velocity of a reaction.
max
V
—when all enzyme sites are filled with the substrate.
max
max
k
1
[S]
value
m
Enzyme inhibition
Enzyme inhibitors—low molecular weight substances
Formed enzyme—inhibitor complex
Section 3 Biochemistry
413412
Act by either reducing or completely blocking the
catalytic activity of the enzyme.
Uncompetitive inhibitor— inhibitors bind only with the
enzyme–substrate complex.
Classification of enzyme inhibitor
1. Reversible inhibitor
2. Irreversible inhibitor
Reversible inhibition occurs when reversible inhibitors bind
to an enzyme with noncovalent interactions like hydrogen
bonds, ionic bonds, and hydrophobic interactions.
Competitive inhibition—the inhibitor binds with free
enzyme not with complex.
Non-competitive inhibition—Inhibitor binding reduces
the enzyme activity, but does not have an effect on the
binding of substrate.
MULTIPLE CHOICE QUESTIONS
1. Which of the following are nitrogenous bases of
the pyrimidine type?
A. Thymine and guanine
B. Guanine and adenine
C. Cytosine and uracil
D. None of the above
2. Which enzyme is found in tears, sweat, and egg
white?
A. Ribozyme
B. Lysozyme
C. Zymogen
D. Isozymes
3. How many hydrogen bonds can a water molecule
potentially take in liquid form?
A. One
B. Two
C. Three
D. Four
4. In the competitive type of inhibition, an inhibitor:
A. Binds at distinct sites of an enzyme.
B. Binds in reversible fashion at the active site
C. Binds only to the ES complex of reaction
D. Binds to the enzyme by covalent bonds
5. Oxidoreductases include:
A. Catalases and mutases
B. Oxygenases and dehydrogenases
C. Dehydrogenases and ligases
D. Aminotransferases and racemases
6. How hydrophobic effect inuences the structures
of large molecules?
A. It is a property of nonpolar molecules that they
are not easily solubilised in water and aggregate
B. Polar groups are oriented on the surface,
Section 3 Biochemistry
interacting with the water
C. Non-polar molecules can hinder the polar-
characteristics of the hydrophilic molecules
D. Both A and B
Irreversible inhibition—inhibitor binds to the enzyme
by covalent attachment. In this type of inhibition catalytic
activity of an enzyme is completely lost.
Factors affecting enzyme activity:
Active site
Temperature and pH
Concentration and type of substrate
Salt concentration.
7. Which amino acid below is least likely to
participate in general acid–base catalysis?
A. Lysine
B. Cysteine
C. Histidine
D. Glycine
8. Myoglobin binding of oxygen depends on:
A. The oxygen concentration (pO2)
B. The hemoglobin concentration
C. The affinity of myoglobin for the O2 (K)
D. Both A and C
9. Regulation of biological nitrogen xation is done
by which of the following enzymes:
A. Dinitrogenase reductase
B. Dinitrogenase oxidase
C. Phosphatase
D. Kinase
10. Out of following which structural feature of DNA
allows it to replicate?
A. Helical structure
B. Sugar-phosphate backbone
C. Complementary base pairing of the nitrogenous
bases between strands
D. None of the above
11. All the following are examples of irreversible
enzyme inhibitors, except:
A. Cyanide
B. Sarin
C. Diisopropyl phosphofluoridate (DIPF)
D. Statin drugs
12. Which of the following activities is possible by
transferases?
A. Transfer of methyl groups
B. Transfer of glycosyl group
C. Both A and B
D. None of the above
13. The following plot most likely represents:
A. A competitive inhibitor
B. An uncompetitive inhibitor
C. A noncompetitive inhibitor
D. A mixed type inhibitor
E. An irreversible inhibitor
14. An allosteric inhibitor of an enzyme usually:
A. Take part in feedback regulation
B. Denatures the enzyme
C. Has hydrophobic characteristics
D. Forces enzyme to work at higher speed
15. True about Henderson-Hasselbalch equation:
A. Determine the graphic of molecular weight of
a weak acid from its pH alone
B. Does not justify the behaviour of di- or tri-basic
weak acids
C. Establish a relationship between the pH of a
solution to the pK
and the concentrations of
a
acid and conjugate base
D. All of the above
16. A competitive inhibitor:
A. Increases the Km of the enzyme
B. Decreases the V
C. Enhance the V
of the enzyme
max
of the enzyme
max
D. Suppress the Km of the enzyme
17. The non-protein part of an enzyme is called:
A. Apoenzyme B. Holoenzyme
C. Allosteric Enzyme D. Isoenzyme
E. Coenzyme
18. Enzymes:
A. Enhance the energy barrier for a reaction
B. Are recovered after reaction completion in
unaltered condition
C. The equilibrium constant of the reaction
D. Activity is subject to regulation
19. Which one is best suited term for serine proteases
when serine side chain react with the scissile
peptide bond?
A. General acid catalysis
B. Electrophilic catalysis
C. Covalent catalysis
D. Electrostatic catalysis
20. The catalytic factor of an enzyme is:
A. The ratio of K
cat/KM
B. The number of substrate molecules → Product
per min per mole enzyme
C. The specificity factor for a given substrate
D. A measure of the ability of an enzyme to
increase the rate of a reaction
21. Regulators of enzymatic reactions are classied
as:
A. Inhibitors B. Converters
C. Activators D. Both A and C
22. For an enzyme which follows Michaelis-Menten
kinetics out of which following statements about
a plot of V
A. Km is equal to [S] when V0 = ½ V
vs. [S] is false?
0
max
B. The shape of the curve is a hyperbola
C. The y-axis of the curve gives rate terms with
units of µm/min
D. At very high [S], the velocity curve gives
horizontal line which intersects the y-axis at K
m
23. Most closely related organic molecule to lipids is:
A. Nucleotide B. Amino acid
C. CH2 chain D. None of these
24. Which of the following statements is correct about
competitive inhibitors?
A. It is a common example of irreversible inhibition
B. In the presence of a competitive inhibitor, the
Michaelis-Menten equation becomes
V
[S]
V0 =
aK
max
+ [S]
m
C. The apparent Km decreases in the presence of
inhibitor by a factor α
D. The maximum velocity for the reaction
decreases in the presence of a competitive
inhibitor
25. The model proposed by Emil Fischer is known as:
A. Arrow and shield model
B. Deduction model
C. Induction model
D. Lock and key model
26. Nucleic acids include:
A. Glucose and glycogen
B. DNA and RNA
C. Lipids and sugars
D. None of the above
27. If one enzyme is involved in glycolysis, aldolase,
requires Zn2+ for catalysis. In zinc deficiency
condition, when the enzyme may lack zinc, it
would be referred to as the:
A. Holoenzyme B. Prosthetic group
C. Apoenzyme D. Coenzyme
28. What is the value of ∆G, when a system is in
equilibrium?
A. DG = 0 B. DG = 1
C. DG = –1 D. DG = ∆DG′
29. Best described model of enzyme action is:
A. Active site model
B. Induced fit model
C. Activator action model
D. None of the above
.
Section 3 Biochemistry
415414
30. Which of these proteases is not a cysteine active
site protease?
A. Calpain B. Cathepsin D
C. Papain D. None of these
31. When an excess of amino acid is added into the
bacterium the rate of the reactions is decreased.
What is the reason for this?
A. End product inhibition
B. Enzyme denaturation
C. Excess substrate causes inhibition of the enzyme
D. Positive feedback reaction
32. When oxaloacetate is formed from bicarbonate
and pyruvate, this process required allosteric
activation (in gluconeogenesis), which one of
following is catalysed by the enzyme pyruvate
carboxylase is?
A. Acetyl-CoA B. Succinate
C. Isocitrate D. Citrate
33. Which of the following is the correct Line weaverBurk equation?
1
A.
V
0
1
B.
V
max
C. V0 =
D. V
max
=
=
V
=
V
K
K
K
m
[S]
max
V0 [S]
[S]
max
+ [S]
m
V0 [S]
+ [S]
m
K
1
+
V
max
+
1
V
0
m
34. Choose the pair of terms that correctly completes
this sentence: Catabolism is to anabolism as ____
is to ____.
A. Exergonic; endergonic
B. Free energy; entropy
C. Work; energy
D. None of the above
35. The organs where gluconeogenesis occur are:
A. Liver and kidney
B. Skin and pancreas
C. Lung and brain
D. Intestine and retina
36. Which of the following are nitrogenous bases of
the purine type?
A. Guanine and adenine
B. Cytosine and guanine
C. Uracil and cytosine
D. All of the above
37. Which one of the following graphs shows the
effect of pH on the reaction velocity of a typical
Section 3 Biochemistry
enzyme?
Note: In each graph, the scale on the X-axis is from
pH 2 to pH 13.
A. I B. II
C. III D. IV
38. A double-stranded DNA molecule has a total
of 120 purines and 120 pyrimidines. This DNA
molecule could be constituted of:
A. 240 adenine and 240 cytosine molecules
B. 120 thymine and 120 adenine molecules
C. 240 guanine and 240 thymine molecules
D. 320 adenine and 210 guanines
39. Law of thermodynamics which states that
energy can neither be created nor be destroyed is
__________ of thermodynamics.
A. The second law
B. Third law
C. First law
D. Zero-order kinetics
40. In the double helix structure of nucleic acids,
cytosine bonds to:
A. Ribose B. Guanine
C. Adenine D. All of these
41. The structure of hexokinase is
A. U-shaped B. S-shaped
C. E-shaped D. L-shaped
42. Michaelis constant of enzyme (Km) is:
A. Equal to substrate concentration at which it
provides maximal velocity
B. Equal to substrate concentration at which it
gives ½ the maximal velocity
C. Equal to ½ the substrate concentration at which
it gives maximal velocity
D. Equal to enzyme concentration at which it gives
maximal velocity
43. Which of the following describe(s) some aspect of
metabolism?
A. Production of macromolecules
B. Breakdown of macromolecules
C. A and B only
D. A, B and C
44. Choose a false statement about chymotrypsin:
A. Hydrolysis of a peptide bond through
chymotrypsin has two phases
B. Activation occurs by trypsin
C. It is formed in the thyroid gland
D. Polypeptide chains have S–S bonds linkage
45. In extrahepatic tissues, one mechanism for
utilization of acetoacetate involves:
A. Malonyl-CoA B. Succinyl-CoA
C. Propionyl-CoA D. Acetyl-CoA
46. Name the process in which large molecules breakdown into small molecules:
A. Catalysis B. Catabolism
C. Anabolism D. Phagocytosis
47. The enzyme which is responsible for catalysation
of the oxidation–reduction reaction is:
A. Transaminase
B. Glutamine synthetase
C. Oxidoreductase
D. Phosphofructokinase
48. In case of myoglobin, when oxygen is bound
to it, that relationship between the oxygen
concentration and the number of binding sites
occupied can best be described as:
A. Hyperbolic
B. Linear with a negative slope
C. Linear with a positive slope
D. All of the above
49. Coenzymes:
A. The non-protein part of enzymes
B. Needed for enzyme activity
C. Termed prosthetic group if bonded tight to their
enzymes
D. All of the above
50. The majority of metabolic pathways are considered
mainly either anabolic or catabolic. Which of the
following pathways is most correctly referred as
an amphibolic?
A. Citric acid cycle B. Gluconeogenesis
C. Lipolysis D. Glycolysis
51. Isoenzymes:
A. Are necessary for enzyme activity
B. Are examples of functional plasma enzymes
C. Show same responses as inhibitor molecules
D. Are play part as an important tool in the
diagnosis and prognosis of disease
52. The isoenzyme LDH5 is elevated in:
A. Myocardial infarction
B. Peptic ulcer
C. Liver disease
D. Infectious diseases
53. Out of the following which one is correct?
A. Apoenzyme + Cofactor = Holoenzyme
B. Apoenzyme – Cofactor = Holoenzyme
C. Apoenzyme = Cofactor – Holoenzyme
D. None of the above
54. Which of the following is incorrect for the lock
and key model?
A. It is used to describe the binding process
B. Enzyme’s active site is complementary to the
substrate
C. It exhibits enzyme–substrate complex
D. When the substrate binds it produces a
conformational change in enzyme
55. On the third day of onset of acute myocardial
infarction, the enzyme elevated is:
A. Serum AST B. Serum CK
C. Serum LDH D. Serum ALT
56. Which of the following catalyzes the reversible
degradation of 2-phosphoglycerate to phosphoenolpyruvate?
A. Chymotrypsin B. Hexokinase
C. Enolase D. Trypsin
57. Acute pancreatitis is produced by:
A. Absence of production of zymogen enzymes
B. Continuous secretion of zymogen enzymes into
the G.I.T
C. Activation of zymogen enzymes before matu-
ration
D. Inactivation of zymogen enzymes
58. An example of functional plasma enzyme is:
A. Lipoprotein lipase
B. Amylase
C. Aminotransferase
D. Lactate dehydrogenase
59. What is the function of phosphorylase?
A. Transfer inorganic phosphate
B. Transfer a carboxylate group
C. Use H2O2 as the electron acceptor
D. Transfer amino group
60. The pH optima for salivary analyse is:
A. 6.6–6.8 B. 2.0–7.5
C. 7.9 D. 8.6
61. A carbohydrate that cannot be digested in the
human gut is:
A. Cellulose B. Starch
C. Glycogen D. Maltose
62. An enzyme has Km = 10 mM and V
= 100 m mol/
max
min. If substrate concentration is [S] = 100 m M,
out of the following which statement will be true?
A. A 10-fold increase in V
would cause 10-fold
max
increase in velocity
B. A 10-fold decrease in Km would cause 10-fold
increase in velocity
C. Both A and B
D. A 10-fold increase in V
would cause 20-fold
max
decrease in velocity
63. The enzyme of the glycolic pathway, sensitive to
inhibition by uoride ions is:
A. Hexokinase
B. Aldolase
C. Enolase
D. Pyruvate kinase
64. Glucose absorption in blood is stimulated through:
A. Vitamin A B. Thiamin
C. Vitamin C D. Vitamin E
Section 3 Biochemistry
417416
65. Which hormone directly acts on intestinal mucosa
and increases glucose absorption in blood?
A. Insulin B. Glucagon
C. Thyroxine D. Oxytocin
66. Out of the following, what is the reason for gout
disease?
A. Deficiency of xanthine oxidase enzyme
B. Over production of xanthine oxidase
C. Deficiency of B-galactosidase enzyme
D. Deficiency of lipase enzyme
67. In the reaction below,
NuTP + glucose →→ →→ → Glucose-6-Phosphate
+ NuDP.
NuTP stands for
A. ATP B. CTP
C. GTP D. UTP
68. The active site of chymotrypsin consists of a
catalytic triad made up of following amino acid
residues.
A. Serine, histidine and aspartate
B. Serine, histidine and glutamate
C. Threonine, histidine and arginine
D. Methionine, lysin and aspartate
69. In erythrocytes, 2, 3-biphosphoglycerate is derived
from which of the following intermediate:
A. Glyeraldehyde-3-phosphate
B. 1, 3-Biphosphoglycerate
C. 3-Phosphoglycerate
D. 2-Phosphoglycerate
70. Cori disease (limit dextrinosis) is caused due to
absence of:
A. Branching enzyme B. Debranching enzyme
C. Glycogen synthase D. Phosphorylase
71. Pepsin and urease are examples of which class of
enzymes:
A. Hydrolases B. Ligases
C. Oxidoreductases D. Lyases
72. An example of an isomerisation reaction is:
A. Glucose-6-phosphate → fructose-6-phosphate
B. 3-Phosphoglycerate → 2-phosphoglycerate
C. 2-phosphoglycerate → Phosphoenolpyruvate
D. Pyruvate → Lactate
73. Pyruvate dehydrogenase activity is inhibited by:
A. Mercury B. Zinc
C. Calcium D. Sodium
74. Who is the father of enzymology?
A. Anton von Leeuwenhoek
B. Edward Howell
C. JB Sumner
D. John Northrop
75. The enzyme, ketoglutarate dehydrogenase in the
Section 3 Biochemistry
citric acid cycle requires:
A. Lipoate B. Folate
C. Pyridoxine D. Inositol
76. Which of the following equations shows the
relationship between free energy change (∆G)
and the change in entropy (∆S), under constant
temperature and pressure?
A. ∆G = T∆H – ∆S B. ∆G = T∆H/∆S
C. ∆G = ∆H/T∆S D. ∆G = ∆H – T∆S
77. Chain elongation of fatty acids in the mammalian
liver occurs in:
A. Nucleus B. Ribosomes
C. Lysosomes D. Microsomes
78. The total number of ATP molecules produced for
each turn of the Kerb cycle is:
A. 8 B. 12
C. 24 D. 38
79. Absence of enzyme β-glucerebrosidase results in:
A. Gauchers disease B. Faber’s disease
C. Krabbe’s disease D. Goiter disease
80. Name of specific inhibitor for succinate
dehydrogenase enzyme is:
A. Arsenine B. Arsenite
C. Citrate D. Arginine
81. Name the enzyme secreted by the pancreas.
A. Pepsin
B. Chymotrypsin
C. Trypsin
D. Alcohol dehydrogenase
82. In a Lineweaver-Burk plot, competitive inhibitor
produces the following effect?
A. Curve moves to right
B. Curve moves to left
C. Changes the x-intercept
D. No change on the slope
83. Dehydrogenases utilize, following as coenzymes, except:
A. NAD+ B. NADP+
C. FAD D. FH4
84. Which of these bonds is not important in
maintaining the structure of the active site?
A. Ionic B. Hydrogen
C. Disulfide D. Phosphodiester
85. The action of glycogen synthase is inhibited by:
A. Insulin B. Glucose
C. Mg2+ D. Cyclic AMP
86. Out of the following (drugs) which is not a specic
enzyme inhibitor?
A. Iodine B. Methotrexate
C. Sulphanilamide D. Penicillin
87. Characteristic feature(s) of the active site is/are:
A. Flexible in nature B. Site of binding
C. Acidic D. Both A and B
88. Name the coenzyme of riboavin:
A. NAD or NADP
B. FAD and FMN
C. Coenzyme A
D. Thiamine pyrophosphate