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Bm2 > Past Paper Questions MCQ > Flashcards

Past Paper Questions MCQ Flashcards

1
Q

Anaerobic dehydrogenases
A. Participate in the Krebs cycle
B. Generate reducing equivalents for the respiratory chain
C. Are specific for NAD but not for NADP
D. Participate in the mechanism of unsaturation of fatty acids
E. If cytoplasmic, they reduce pendulum enzymes

A
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2
Q

Oleic acid
A. It is synthesized by unsaturation from palmitic acid (By Stearic acid)
B. It is omega 6 (It is omega 9 acid)
C. It is a precursor of linoleic acid in mammals (It is not a precursor)
D. It is obtained by unsaturation of a FAD dependent enzyme

A
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3
Q

The oxidation of phytanic acid allows
A. Produces butyryl-CoA
B. Produces propionyl-CoA
C. It is performed in plants by cellulose
D. It is chlorophyll side chain origin

A
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4
Q

The anhydride bond of ATP is “high energy” because
A. DG«0
B. Protons are released
C. The products are less hydrated than the reactants
D. It is unstable
E. The charge density in the reactants is higher than in the products

A
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5
Q

Fructose 2,6-bisphosphate is
A. Synergistic with ATP in its effect on glycolysis
B. Inhibits phosphofructokinase-1 (PFK1)
C. Increases in the liver under conditions of hypoglycemia
D. It is citrate antagonist in its effect on glycolysis
E. It is produced under insulin stimulation

A
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6
Q

AMPK (AMP kinase)
A. Activates acetyl-CoA carboxylase
B. Inhibit mTOR
C. Activates cholesterol synthesis
D. Does not require phosphorylation to be activated
E. Its effects on metabolism are comparable to those of PKC

A
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7
Q

Succinic (succinate) dehydrogenase
A. Transfers electrons to an FMN
B. Transports protons out of the matrix
C. Transfers electron to a FAD
D. Uses succinyl-CoA as a substrate

A
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8
Q

Alternative inputs of oxidative phosphorylation are
A. Glycerol-3-Phosphate dehydrogenase
B. Acyl-CoA dehydrogenase
C. Succinyl-coa synthetase

A
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9
Q

Oxygen
A. Reacts with reduced carbon with low activation energy
B. Can receive two electrons simultaneously from a flavin enzyme
C. Produces a radical when reduced with two electrons
D. Has four unpaired electrons in antibonding orbitals
E. In superoxide form it is a powerful oxidizer

A
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10
Q

The de novo synthesis of purines implies that
A. They are synthesized as nucleotide derivatives
B. The first purine of the biosynthesis pathway is GMP
C. Folic acids are not involved
D. Pyrimidines are synthesized
E. AMP is synthesized from GMP

A
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11
Q

PKC (protein kinase C)
A. Is activated when attached to the membrane
B. Is activated by diacylglycerol
C. Phosphorylates tyrosine residues in the SH2 domains
D. Activates glycogenolysis
E. Is activated by Calcium

A
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12
Q

Insulin directly or indirectly

A. Activates lipolysis in adipose tissue
B. Indirectly activate Acetyl - CoA carboxylase
C. Activates GLUT-2
D. Activates the MAP kinase cascade
E. Activates FOXO

A
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13
Q

Nitric oxide
F. Is a free radical
G. Reacts with thiol (SH2) groups
H. SH - Inhibits adenylate cyclase
I. Transforms into NO2
J. Activates cGMP phosphodiesterase

A
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14
Q

Gluconeogenesis
E. Is stimulated under conditions of massive fatty acid oxidation
F. Does not utilize the carbon skeleton of ketogenic amino acids to form glucose
G. Utilizes long-chain fatty acids to form glucose
H. Requires NADH
I. Occurs in tissues distinct from those that make ketogenesis

A
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15
Q

The transcription factor HIF
E. Promotes mitochondrial respiration
F. Promotes the expression of glucose transporter with high affinity
G. Inhibits angiogenesis
H. Promotes glycolysis
I. Promotes transcription of cytoprotective genes

A
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16
Q

About purines
F. Xanthine is more oxidized than hypoxanthine
G. Uric acid is formed only if the nitrogenous base is adenine
H. Catabolism of purine nucleotides occurs when nucleoside monophosphate is formed
I. Gout could result from a increased activity of phospho-ribosyl pyro-phosphate (PRPP)
synthetase or a deficiency of the salvage enzyme
J. Allopurinol is a drug structurally unrelated to purines

A
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17
Q

About free fatty acids
F. In general, they depress glucose metabolism
G. In the plasma they travel linked to LDL
H. They contain more calories than sugars for the same weight
I. Their synthesis is stimulated by glucagon
J. NADPH can be formed from their oxidation

A
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18
Q

The pentose phosphate pathway
F. uses at least one biotin dependent enzyme
G. includes at least one irreversible reaction
H. generates NADH (H+)
I. forecasts the net production of CO2

A
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19
Q

Trans fatty acids
E. Sometimes it is a part of human diet
F. It only exists in the grain and plants
G. It can be produced artificially
H. It is unsaturated fatty acids

A
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20
Q

Zero kinetic order

A
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21
Q

VLDL

A
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22
Q

Protein kinase C

A
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23
Q

Plasmalogens

A
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24
Q

Triplet oxygen/reactivity/electrons involved

A
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25
Q

Inosine

A
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26
Q
  1. In the synthesis of purines participates:
    - The Tetrahydrofolic acid (THF)
    - A Glutamic Acid
    - The Thiamine
    - An Aspartic Acid
    - A Carbonic Acid
A

A, B and D
Thiamine- used in carbohydrate metabolism
Carbonic acid- respiration, H2CO3 reduces CO2 levels.

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27
Q

Effects of HIF

A
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28
Q

Guanylate Cyclase

A
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29
Q

Calcium and insulin

A
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30
Q

Transdeamination

A
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31
Q

Combining reactions with their cofactors.

A
32
Q

G protein

A
33
Q

ALAS

A
34
Q

Alpha ketoglutarate dehydrogenase

A
35
Q
  1. About Cytochrome C Oxidase:
    - It works as a proton pump
    - It transfers four electrons to molecular oxygen
    - It contains two copper (Cu) centers
    - It is an aerobic dehydrogenase
    - It contains a non-heme iron atom
A

This enzyme oxidase molecular oxygen and form H2O in respiration. Terminal electron acceptor in ETC.
Only D is wrong.
A- pump H+ ions across the inner mit. Membrane
B- reduce O2(molecular oxygen)
C-True Copper A and B
D- it is a terminal oxidase not a dehydrogenase. (Dehydrogenase remove H atoms which cytochrome C oxidase reduce O2 to H2O.

36
Q
  1. Guanylate cyclase
    - It is activated by the interaction of heme ferric iron and nitric oxide
    - It exists in a soluble and a membrane form
    - It is activated by phosphoinositides
    - In the active form it does not contain a prosthetic group
A

A and B is true
It is exist in two forms; membrane bound and soluble form so B is true.
Soluble guanylate cyclase is activated when it interacts with nitric oxide(NO), which binds to the heme iron center within the enzyme. This binding leads to the synthesis of the cGMP.
Prosthetic group meaning non protein component such as iron atom and yes it has.
No calmodulin(bind to the excess Ca in the cellular processes)

37
Q
  1. Nitric Oxide (NO):
    - It produces an increase in [Ca]
    - It binds to cytochrome oxidase
    - It activates to vasodilation
    - It activates a vasoconstriction
    - It binds to Guanylate cyclase
A

B,c,e are correct a and d is false
NO vasodilation(Lower BP) so
C is true and it also bind to the Guanylate cyclase. Binding activates the sGC.
NO can bind cytochrome C oxidase and lead to the diminished ATP production.

38
Q

G proteins are so called because:
A- They bind reduced Glutathione
B- They bind oxidized glutathione
C- They bind to Guanine derivative
D- They bind GDP in the activated form
E- They are rich in Glycine

A

C.
Their interaction with Guanosine nucleotide, specifically GDP and GTP

39
Q

VLDL:
- They are synthesized exclusively in the cytosol
- They transfer triglycerides to HDLs
- They mainly contain esterified cholesterol
- They receive esterified cholesterol from HDL during their metabolism
- They contain only the apolipoprotein apoB-100

A

Only D is correct
Begins in ER and golgi not cytoplasm A is false.
B is not true= VLDLs primarily transport 3TG from liver to peripheral tissues. HDLs transport it back to the liver. HDL is named good cholesterol.
C is wrong, they carry normal cholesterol not esterified cholesterol.
D is true,
Majorly apoB-100 but also contain others. So E is wrong also. Apolipoproteins are the surface receptors of the lipoprotein particles.

40
Q

By two-electron reduction of molecular oxygen, is produced:
- Triplet oxygen
- Water
- An unstable radical
- Superoxide
- Hydrogen peroxide

A

Water
O2+ 2e+2H+=2H2O

41
Q

Phosphoribosyl pyrophosphate:
- It intervenes in the savage pathway” of pyrimidines
- It is the precursor of pyrimidine synthesis
- It is the precursor of purine synthesis
- Its formation from ribose-1-phosphate is controlled by feedback
- It reacts with hypoxanthine to form IMP

A

PRPP is important in the nucleotide synthesis.
Let’s evaluate each statement:

  1. It intervenes in the “salvage pathway” of pyrimidines: True. Phosphoribosyl pyrophosphate (PRPP) is involved in the salvage pathway, providing the ribose-5-phosphate necessary for the conversion of free bases (like uracil) into nucleotides.
  2. It is the precursor of pyrimidine synthesis: True. PRPP is a precursor in the de novo synthesis of both purines and pyrimidines.
  3. It is the precursor of purine synthesis: True. PRPP is a precursor in the de novo synthesis of purine nucleotides.
  4. Its formation from ribose-1-phosphate is controlled by feedback: False. Generally controlled by the presence of substrates etc. not feedback inhibition.
  5. It reacts with hypoxanthine to form IMP: True. PRPP reacts with hypoxanthine in the presence of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) to form inosine monophosphate (IMP), a precursor in purine nucleotide synthesis.

So, statements 1, 2, 3 and 5 are true.

42
Q
  1. The Transitional State of the Enzyme-Substrate Complex (ES):
    - It is relevant only in irreversible reactions
    - It is at an energy level lower than that of the products.
    - It is more stabilized than ES
    - It is independent of conformational adjustments
    - Its energy levels is the main determinant of the speed on the reaction
A

E true rest is wrong.
A-No, it is relevant in both
B-Transition state is higher than both the reactants and products.
C- less stable than the ES complex, highly reactive transition state.
D-Nope, conformation is important

43
Q
  1. Select the correct answer (or answers) about Enzyme- Coenzyme Association
    - Transaminase - Pyridoxal phosphate
    - Lactic dehydrogenase - NADP
    - Glucose-6-phosphate dehydrogenase - NAD
    - Pyruvate dehydrogenase - Pyridoxal phosphate
    - Amino acid oxidase - Biotin
A

Only A Is correct
B-Lactic dehydrogenase should be NAD+
C-Glucose-6-Phosphate should be NADP+
D- Pyruvate dehydrogenase uses TPP,lipoic acid and FAD
E-Biotin used with carboxylases

44
Q
  1. The Michaelis and Menten equation describing enzyme kinetics implies some assumptions. Which of
    the following are correct
    - That at maximum speed the enzyme is not saturated by the substrate
    - That the substrate-enzyme complex is not formed
    - That the enzyme concentration is much higher than that of the substrate
    - That no product accumulates during the measurement time
    - That the concentration of the enzyme substrate complex (ES) is constant during the
    measurement time
A

The free ligand approximation assumption - substrate concentration being higher than the enzyme concentration(excess of substrate)
The steady state assumption - The rate of product formation stays constant
The irreversibility assumption - Basically meaning the reaction only goes forward (i.e. one direction) and that the products never revert
E is true. ES complex constant during the initial phase of the reaction.

45
Q
  1. The omega oxidation of fatty acids:
    - It involves the formation of dicarboxylic acids
    - It is a predominant metabolic pathway in a normal subject
    - It involves a reaction catalyzed by a mixed function oxidase
    - It involves the oxidation of the carbon atom closest to the carboxylic group of the fatty acid
    - It occurs exclusively in the mitochondria
A

A and C are correct
B is wrong because primary pathway is the Beta oxidation of the fatty acids.
D is wrong because it is furthest from the carboxyl group
E is also wrong because it occurs in the ER(smooth)
A is correct when we oxidase we ended up with dicarboxylic acid
C is correct cytochrome P450

46
Q
  1. About the enzyme that converts phenylalanine to tyrosine:
    - It can be considered a mixed function oxidase
    - It is an oxidoreductase
    - It uses NADH as a source of reducing power
    - it requires tetrahydrofolic acid for its functioning
    - It uses molecular oxygen to for tyrosine
A

Name: phenylalnine hydroxylase(PAH)
B and E are correct
A= it is not a mixed function oxidase such P450
B=hydroylation of the phenylalanine, converting it to tyrosine, by transferring electrons and reducing O2 to form H2O
C=Nope it uses BH4(tetrahydrobiopterin)
D=It doesn’t use TFL
E=it uses molecular oxygen to make water.

47
Q
  1. Delta aminolevulinic acid (ALA)
    - It Requires aspartate for the synthesis
    - It requires pyridoxal phosphate for its synthesis
    - It requires an intermediate of the Krebs cycle for its synthesis
    - It is the direct precursor of porphobilinogen
    - Its synthesis is stimulated by the heme
A

B,C,D is correct others are false.
A=it doesn’t need aspartate, it needs glycine and succinyl-coA
E= it is not stimulated by the heme, it is regulated negatively by the heme. High levels of heme inhibit the enzyme responsible for the first step of ALA synthesis.
B=correct B6
C=yes succinyl-coA
D=yes direct precursor of PBG in heme synthesis

48
Q
  1. Which coenzymes are involved in the alpha-ketoglutarate dehydrogenase reaction:
    - Biotin
    - FAD
    - Pyridoxal phosphate
    - FMN
    - Thiamine pyrophosphate (TPP)
A

Large 3 enzyme complex
Thiamine pyrophosphate
FAD
Lipoic acid
Correct answer: B and E

49
Q
  1. In mitochondrial beta-oxidation, beta-hydroxy acyl-CoA dehydrogenase:
    - It requires FAD
    - It is an anaerobic dehydrogenase
    - It transforms a hydroxyl group into a ketone group
    - It produces superoxide ion
    - It requires NAD
A

A,C and E
Requires NAD and FAD and it catalyzes the dehydrogenation of a beta-hydroxy group in a fatty acyl-CoA molecule to form a Beta-keto group
B= it is aerobic not anaerobic
D= it doesn’t produce superoxide ion.

50
Q
  1. The pentose-phosphate pathway:
    - It reduces NADH
    - It is stimulated by insulin
    - It is connected to the synthesis of purines
    - It requires the involvement of mitochondrial enzymes
    - It is very active in cells in the proliferative phase
A

2,3,5
1= it doesn’t use NADH instead using NADPH
4= it happens in the cytoplasm no mit. Enzyme required

51
Q
  1. The enzyme glucose-6-phosphate dehydrogenase:
    - It is redox-sensitive
    - It is deficient in subjects affected by favism
    - It forms ribulose-5-phosphate
    - It catalyzes an irreversible reaction
    - It serves to get glucose out of the cell
A

1,2,4 is true
It is redox sensitive
G6PD deficiency is a genetic condition known as favism
3= it forms 6-phosphoglucono-δ-lactone, not ribulose-5-phosphate

52
Q
  1. S-adenosyl methionine
    A- It receives methyl groups from Tetrahydro biopterin
    B- It is involved in the synthesis of phosphatidyl ethanolamine
    C- It methylates the amino groups
    D-It is involved in the synthesis of glycosides
    E-It turns into S-adenosyl homocysteine
A

b,C,e are correct
A= SAM itself is a methyl donor
D=glycosides are formed through glycosylation reactions, which is transfer of sugar not methyl.

53
Q

20.inosine
a- it is a direct precursor of Xanthine
B-it produces ribose-1-phosphate
C- it derives from the IMP for dephosphorylation
D-It can be made from guanine
E-It is produced by deamination of adenosine

A

A,c,d,e
A= inosine is a precursor in the degradation pathway of purines, it can be converted into the xanthine.
B= ribose-1-phosphate produced in the PPP
C=IMP can be dephosphorylated to form inosine. IMP’s an intermediate in purine synthesis and degradation.
D=guanine can be deaminated to form xanthine, which can be further converted into inosine. (Guanine-xanthine-inosine)
E=

54
Q
  1. About purines:
    - Xanthine is more oxidized than hypoxanthine
    - Gout could result from increased activity of phosphoribosyl pyrophosphate (PRPP) synthetase
    or from a deficiency in the rescue enzyme
    - Uric acid is formed only if the nitrogen base is adenine
    - The catabolism of purine nucleotides occurs when the monophosphate nucleoside is formed
    - Allopurinol is a drug not structurally related to purines
A
55
Q
  1. Insulin directly or indirectly:
    - It activate FOXO1
    - It activates the MAP Kinase cascade
    - Indirectly it activates Acetyl-CoA Carboxylase
    - It activates lipolysis in the adipose tissue
    - It activates Glut-2
A
56
Q
  1. The PKC (Protein kinase C):
    - It is activated by Diacylglycerol
    - It activates glycogenolysis
    - It is activated by Calcium
    - It is activated when it is attached to the membrane
    - It phosphorylates tyrosine residues of SH2 domains
A
57
Q
  1. Succinic dehydrogenase:
    - It carries protons out of the matrix
    - It is soluble in the mitochondrial matrix
    - It transfers electrons to FAD
    - it transfers electrons to FMN
    - It uses succinyl-CoA as substrate
A
58
Q
  1. In a zero-order kinetics:
    - The half-life is constant
    - If enzymatic, it indicates the saturation of the ES complex
    - The temperature does not affect the speed
    - The rate is dependent on substrate concentration
    - The substrate wears out at a constant rate
A
59
Q
  1. The anhydride bond of ATP is “high energy because:
    - Products are less hydrated than reagents
    - It is unstable
    - Protons are released
    - TheDGo«0
    - The charge density in the reagents is higher than in the products
A
60
Q
  1. The pentose-phosphate pathway:
    - It requires the involvement of mitochondrial enzymes
    - It is related to the synthesis of purines
    - It is minimally active in the muscles
    - It is very active in the cells that are in their proliferative phase
    - It produces NADH
A
61
Q
  1. Unsaturated fatty acids containing double bonds in trans configuration
    - They are oxidized to propionyl-COA
    - They are not common in nature, but can be industrially produced
    - They do not enter the mitochondria
    - They can only be of animal origin
  • They may be part of the human diet
A
62
Q

Oleic acid:
- It is a typical omega-6 fatty acid
- It is directly formed by desaturation of palmitic acid
- In mammals is a precursor of the linoleic acid(9,12)
- It is produced by a desaturase that requires iron
- It is produced by a desaturase that requires FAD

A
63
Q

About free fatty acids:
- At equal weight they contain more calories than sugars
- NADPH can be formed from their oxidation
- Their synthesis is stimulated by glucagon
- In general they depress carbohydrate catabolism
- In plasma they travel bound to LDL

A
64
Q

Oxygen:
- In its superoxide form (O2-), it is a powerful oxidant
- It has four unpaired electrons in antibonding orbitals.
- It produces a radical when reduced with two electrons
- It can receive two electrons simultaneously from a flavin enzyme
- It reacts with reduced carbon with low activation energy

A
65
Q

The ex-novo synthesis of purines implies that:
- AMP is synthesized by GMP
- The first purine of the biosynthesis pathway is guanosine monophosphate
- Folic acids are not involved
- They are synthesized as nucleotide derivatives
- They are synthesized from pyrimidines

A
66
Q

About AMPK (AMP kinase):
- It does not require phosphorylation for its activation
- It inhibits mTOR
- It activates acetyl-CoA carboxylase
- It activates the synthesis of cholesterol
- Its effects on metabolism are comparable to those of PKC

A
67
Q

Gluconeogenesis:
- It occurs in tissues that are different from those that do ketogenesis
- It requires NADH
- It is stimulated in conditions of massive oxidation of fatty acids
- It does not use the carbon skeleton of exclusively ketogenic amino acids to form glucose
- It uses long chain fatty acids to form glucose

A
68
Q

Fructose 2,6 bisphosphate:
- It inhibits Phosphofructokinase-1 (PFK1)
- It is a citrate antagonist in its effect on glycolysis
- It increases in the liver under hypoglycemic conditions
- It is produced under insulin stimulation
- It is synergistic with ATP in its effect on glycolysis

A
69
Q

Select which are the alternative entries of oxidative phosphorylation:
- Glycerol-phosphate dehydrogenase
- Succinil-CoA synthetase
- Acyl-CoA dehydrogenase
- Alpha-ketoglutarate dehydrogenase
- Succinate dehydrogenase

A
70
Q
  1. Anaerobic dehydrogenases:
    - They participate in the Krebs Cycle
    - If cytoplasmic, they reduce the shuttle coenzymes
    - They generate reducing equivalents for the respiratory chain
    - They are specific to NAD but not NADP
    - They participate in the mechanism of unsaturation of fatty acids
A

B and E
Anaerobic dehydrogenase is an electron transporter used in lack of the oxygen so processes like Krebs cycle it is not used because we use oxygen in the krebs.
So A is wrong.
B is true they indeed reduce NAD+ and FAD+
C is wrong
D is wrong they can be used both NAD and NADP
E is true

71
Q
  1. About the transcription factor HIF (hypoxia-inducible factor):
    - It promotes glycolysis
    - It inhibits angiogenesis
    - It promotes the expression of high-affinity glucose transporters
    - It promotes mitochondrial respiration
    - It promotes lipolysis
A
72
Q
  1. Phytanic acid:
    - It produces Butyryl-CoA
    - it produces Succinil-CoA
    - It is a product of the digestion of chlorophyll
    - It is produced by methylation of linear fatty acids
    - It produces formic acid in its metabolism
A
73
Q
  1. Nitric Oxide:
    - It is a free radical
    - It turns into NO2
    - It Reacts with thiol groups -SH-
    - It inhibits Adenylate cyclase
    - It activates cGMP phosphodiesterase
A
74
Q

Coenzyme Q

A
75
Q

Glut 2 transporter

A

Bm2 (2 decks)

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