BIOCHEMISTRY-LE-8 (2024) Flashcards by

The class of immunoglobulins which can cross the placenta is:
A. IgM
B. IgG
C. IgA
D. IgD

IgG

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Self-reactive antibodies are not found in significant concentration in normal serum because:
A. It is impossible to generate a self-reactive antibody
B. Self-reactive B cells are killed by CD8 T cells
C. B cells that are stimulated via their surface bound antibody in the absence of T cell help to commit suicide
D. Self-reactive B cells switch to lgA which is all secreted and not present in serum

B cells that are stimulated via their surface bound antibody in the absence of T cell help to commit suicide

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Simulation of which of the following will lead to appearance of first antibody to appear following stimulation by an antigen?
A. IgM
B. IgA
C. IgE
D. IgG

IgM

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Antigen binding sites of an immunoglobulin are located in:
A. Light chain alone
B. Heavy chain alone
C. Fc region of the antibody
D. Fab regions of the antibody

Fab regions of the antibody

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Which of the following mediates Type I hypersensitivity reaction?
A. IgE
B. IgG
C. IgM
A. IgD

IgE

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Which of the following theory of antibody production is most widely accepted?
A. Side chain theory
B. Clonal selection theory
C. Direct template theory
D. Indirect template theory

Clonal selection theory

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Which is the most efficient complement fixing class of antibody?
A. IgE
B. IgA
C. IgM
D. IgG

IgM

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The class of immunoglobulin, most abundant in body is:
A. IgD
B. IgE
C. IgG
D. IgM

IgG

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Which is not a function of IgG?
A. Major antibody inserum
B. First antibody type produced against an antigen during the primary antibody response
C. Activates or fixes complement
D. Involved in opsonisation

First antibody type produced against an
antigen during the primary antibody response

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J chain is present in:
A. IgA
B. IgG
C. IgD
D. IgE

IgA

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Heat-labile class of immunoglobulins include:
A. IgA
B. IgE
C. IgG
D. IgM

IgE

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Which of the following is the phylogenetically oldest immunoglobulin?
A. IgE
B. IgM
C. IgG
D. All are similar

IgG

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The secretary component of sigA is:
A. Made by plasma cells that secrete dimeric IgA
B. Added to dimeric IgA by the M cell
C. Formed by cleavage of an epithelial cell receptor used to transport the dimeric IgA across the epithelial cell
D. Made by T cells

Formed by cleavage of an epithelial cell receptor used to transport the dimeric IgA across the epithelial cell

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Anti-Rh antibodies are:
A. IgG type
B. IgA type
C. IgE type
D. IgD type

IgG type

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Which is not a function of IgA?
A. Protect mucosal surfaces
B. Fix complement
C. Protect eyes
D. Agglutinate antigen

Fix complement

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Which immunoglobulin is the principal one found in secretions such as milk?
A. IgG
B. IgM
C. IgA
D. IgE

IgA

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Which of the following statements best characterizes an antibody:
A. It contains high molecular weight RNA as its basic structure
B. Is composed of protein and cannot be distinguished from the albumin fraction of the serum proteins
C. Is composed of four identical protein subunits which may be caused to dissociate by treatmentwith urea
D. Contains protein as its major chemical component and its synthesis may be elicited by the administration of a foreign protein or polysaccharide

Contains protein as its major chemical component and its synthesis may be elicited by the administration of a foreign protein or polysaccharide

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The immunoglobulin class which is the least abundant in the normal adult is:
A. IgG
B. laA
C. IgD
D. IgE

IgE

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Light chains are:
A. Specific for each class of antibody
B. Not specific for each class of antibody
C. Reactive with antigen
D. Have only a constant region

Not specific for each class of antibody

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Which of the following statement is true regarding F region:
A. Fragment crystallization and is the constant region
B. Fragment constant and is the variable region
C. Fragment crystallization and is the variable region
D. Fragment crystallization and has both variable and constant region

Fragment crystallization and is the constant region

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Fab region:
A. Has a hypervariable region that binds with antibody
B. Has a hypervariable region that binds with antigen
C. Has a hypervariable region that binds with other immune cells
D. All of the choices

Has a hypervariable region that binds with antigen

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The ability of antigen to stimulate antibody production is termed:
A. Affinity
B. Antigenicity
C. Elicitation
D. None of the choices

Antigenicity

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Monomers of certain immunoglobulins are joined by:
A. Variable chain
B. Constant chain
C. J-chain
D. All of the choices

J-chain

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The two identical light chains of an antibody belongs to:
A. Kappa only
B. Lambda only
C. Lambda or kappa
D. None of the above

Kappa only

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25. The hypervariable region of antibody consists of: A. Amino acids that form antigen binding site B. Phospholipids that form antigen binding site C. Oligosaccharides that form antigen binding site D. A part of the constant region of heavy and light chains

Amino acids that form antigen binding site

26. True of xenobiotics: A. They are alternative sources of ATP in the absence of macronutrients B. They are excreted by the body unchanged C. They do not undergo first pass metabolism D. Catabolism by CytP450 makes them more water soluble

Catabolism by CytP450 makes them more water soluble

27. What is/are the principal site/s for xenobiotic metabolism? A. Lungs B. Liver C. Kidneys D. Liver and kidneys

Liver

28. In general, xenobiotic drugs are manufactured as which of the following to facilitate absorption? A. Water-soluble B. Fat-soluble C. Highly polar D. Hydrophilic

Fat-soluble

29. The main goal of xenobiotic metabolism: A. Render the molecule water-soluble B. Avoid liver catabolism to enable a higher bioavailability C. Excrete the xenobiotic via the fecal route D. Increase the lipophilic character of the xenobiotic for better cellular absorption

Render the molecule water-soluble

30. Which organ is least involved in xenobiotic metabolism? A. Intestine B. Brain C. Kidney D. Liver

Brain

31. True of cytochrome P450. A. It catalyzes phase II of xenobiotic metabolism B. It is a selenium-containing enzyme C. It helps synthesize steroid hormones D. It inactivates Vitamin D

It helps synthesize steroid hormones

32. How are cytochrome P450 enzymes related to drug interactions? A. They induce the lungs to volatilize drugs that enter the bloodstream B. Some drugs are catabolized by the sameCytP450 enzymes C. Because of their monomorphic nature, only one CyP450 breaks down drugs that enter the bloodstream D. The hemeproteins in Cyt450 are responsible for promoting antibiotic resistance

Some drugs are catabolized by the sameCytP450 enzymes

33. All of the following are true of free radicals EXCEPT: A. Increasing intake of antioxidants will halt free radical synthesis B. They are formed even in normal conditions C. They cause damage to nucleic acids, proteins, and lipids D. Formation of free radicals can cause self-perpetuating chain reactions

Increasing intake of antioxidants will halt free radical synthesis

34. The reaction 02 + 2H* -> H202 is catalyzed by: A. Catalase B. Glutathione peroxidase C. Superoxide dismutase D. Cytochrome P450

Superoxide dismutase

35. Which of the following is an important cofactor for vitamins C, E, and Glutathione Peroxidase in the neutralization of free radicals? A. NADPH B. Bioflavinoids C. Selenium D. Copper

NADPH

36. What is the adduct that attaches to red blood cells in HbA1C that is used as a diagnostic marker? A. Fructose B. Alanine C. Heme D. Glucose

Glucose

37. This phytochemical is usually found in grapes: A. Resveratrol B. EGCG C. Curcumin D. Ferulic acid

Resveratrol

38. What DNA repair mechanisms is used to correct DNA damage caused by the formation of thymine-thymine dimers due to ultraviolet light? A. Base excision B. Nucleotide excision C. Single strand break D. Homologous recombination

Nucleotide excision

39. This is a toxic protein aggregate that is the hallmark of diseases such as Parkinson's and Alzheimer's disease: A. Schiff base B. Amyloid C. Amylopectin D. Amadori intermediate

Amyloid

40. What is the role of telomeres in the aging process? A. Telomeres cause a progressive slowing down of an individual's heart rate when they accumulate with age B. Telomeres shorten after every cell division until senescence sets in C. Telomeres generate Okazaki fragments, which are not detected by DNA polymerases during cell replication of DNA D. In theory, telomeres generate protein aggregates which when expressed will cause DNA damage

Telomeres shorten after every cell division until senescence sets in

41. All of the following organisms/cells are studied extensively as model organisms in aging studies, EXCEPT: A. Xenopus sp. cells B. Drosophilia melanogaster C. HeLa cells D. C. elegans

HeLa cells

42. All the biochemical reactions involved in the conversion of foreign, toxic, and water insoluble molecules are called: A. Entoxification B. Excretion C. Biotransformation D. Transversion

Biotransformation

43. The functional group introduced in phase 1 of the metabolism of xenobiotics: A. -NH3 B. -OH C. -CH3 D. =O

-OH

44. The major reaction involved in phase 2 of the metabolism of xenobiotics is: A. Conjugation B. Methylation C. Peroxygenation D. Dehalogenation

Conjugation

45. What is the role of transgenic organisms in the study of xenobiotics? A. Transgenic organisms may be introduced into other animals to metabolize xenobiotics B. Transgenic organisms may be used for drug synthesis C. Xenobiotics can form non-toxic transgenic organisms D. All of the above

B. Transgenic organisms may be used for drug synthesis

46. Which of the following statements is true? A. The bigger the animal, the longer the lifespan B. The slower the metabolic rate, the longer the lifespan C. Both A and B are true D. Both A and B are false

Both A and B are true

47. If a xenobiotic is a prodrug, what happens after phase 1 of its metabolism? A. It is converted to a carcinogen B. It becomes more lipophilic C. It becomes therapeutically active D. It is excreted unchanged in the urine or feces

It becomes therapeutically active

48. The gene for CYP1A1 is: A. CYP1A in bold letters B. CYP1A1 - underlined C. CYP1A1 - italicized D. CYP450

CYP1A1 - italicized

49. Which amino acid is not present in glutathione? A. G B. E C. C D. Q

50. The most reactive free radical is: A. Hydroxyl B. Superoxide C. Hydrogen peroxide D. Water

Hydroxyl

51. In the context of a prokaryotic gene expression which of the following is the most appropriate definition of an operator? A. A cluster of genes that are regulated by a single promoter B. A DNA binding protein that regulates gene expression C. A non-coding regulatory DNA sequence that is bound b RNA D. A non-coding regulatory DNA sequence that is bound by a repressor protein

A non-coding regulatory DNA sequence that is bound by a repressor protein

52. In terms of lac operon regulation, what happens when E. coli is grown in medium containing glucose and lactose? A. Both CAP and the lac repressor are bound to the DNA B. CAP is bound to the DNA but the lac repressor is not C. Lac repressor is bound to the DNA but CAP is not D. Neither CAP nor the lac repressor gene are bound to the DNA

Neither CAP nor the lac repressor gene are bound to the DNA

53. Nuclear receptors belong to what class of transcription factor? A. Helix loop helix proteins B. Helix turn helix proteins C. Leucine zipper proteins D. Zinc finger proteins

Zinc finger proteins

54. Which of the following statements regarding the regulation of trp operon expression by attenuation is correct? A. The leader peptide sequence encodes enzymes related to tryptophan synthesis B. The leader peptide sequence contains no tryptophan residues C. Rapid translation of the leader peptide allows completion of the mRNA transcript D. Rapid translation of the leader peptide prevents completion of the mRNA transcript

Rapid translation of the leader peptide prevents completion of the mRNA transcript

55. RNA I stands for which of the following? A. RNA inducer B. RNA insertion C. RNA interference D. RNA intron

RNA interference

56. Which of the following is true of the Lac operon in E. coli? A. The operon is only switched on in the absence of lactose in the growth medium B. The lac operon messenger RNA is a polycistronic mRNA C. The enzyme B galactosidase is only produced in large quantities when the lac repressor is bound to the operator D. The promoter is the binding site for the lac repressor

The lac operon messenger RNA is a polycistronic mRNA

57. Which of the following statements about mRNA stability is correct? A. Eukaryotic mRNAs have a half-life of only a few minutes B. Regulation of mRNA stability is a way of regulating gene expression C. It is thought that poly A tails stabilize prokaryoticRNAs D. Histone mRNAs have especially long poly A tails and are especially stable

Regulation of mRNA stability is a way of regulating gene expression

58. An epigenetic change in gene expression is an inherited change that does not involve any change in the nucleotide sequence of the gene A. True B. False

TRUE

59. Which of the following statements is true of RNA interference A. Is a normal way for organisms to regulate gene expression B. Is a mechanism for combating virus infection inplants C. Occurs only in vertebrates D. Is already used therapeutically in many disorders

Is a normal way for organisms to regulate gene expression

60. Gene regulation in bacteria is important in order to: A. Prevent wasting energy B. Enable response to environmental stimuli C. Allow cells to adjust promptly to changes in the growth medium D. All of the above

All of the above

61. Examples of internal stimuli originating from within the organism that coordinate gene expression include all of the following except: A. Steroid hormone B. Growth factors C. Sunlight D. HSP70

C. Sunlight

62. Which statement is incorrect? A. Gene regulation is fundamental to cell specialization in multicellular organisms B. Patterns of gene expression established during the early developmental stages are not permanent, enabling one cell type to differentiate in a different cell type later in the life cycle C. Some gene family members are expressed at different phases of development D. Post transcriptional and post translational processing events can regulate the synthesis rate of gene products.

Patterns of gene expression established during the early developmental stages are not permanent, enabling one cell type to differentiate in a different cell type later in the life cycle

63. Which among the following statements is true regarding an operon? A. Cluster of genes transcribed by multiple mRNA B. Genes for multiple genetic pathways C. Can be switched off by a corepressor D. Gene transcription is prevented by the blocking of RNA polymerase

Gene transcription is prevented by the blocking of RNA polymerase

64. Which of the following is correctly matched? A. Lactose: glucose and fructose subunits B. Lac: structural gene C. Permease: transports lactose to the outside of the cell D. Operon: one promoter transcribes more than one gene as a single mRNA molecule

Operon: one promoter transcribes more than one gene as a single mRNA molecule

65. Proteins to be degraded are tagged with: A. Hydroquinine B. Ubiquitin C. Proteasome D. Allolactose

Ubiquitin

66. An example of cleavage modification in eukaryotes is: A. Crystallin gene B. Preproinsulin C. Acetylation D. Methylation

Preproinsulin

67. The location where the lactose repressor gene binds to the lactose operon is called: A. Operator B. Promoter C. Inducer D. Enhancer

Operator

68. When the lactose repressor is bound to the lactose operon: A. Lactose but not glucose metabolism occurs B. The transcription of lac is blocked C. Access to the promoter by RNA polymerase is blocked and transcription of the operon does not occur D. The repressor is unable to bind to its allolactose

Access to the promoter by RNA polymerase is blocked and transcription of the operon does not occur

69. If lactose and glucose are both provided in the growth medium: A. Both lactose and glucose are metabolized at similar rates B. The lactose operon is not transcribed C. Lactose metabolism is favored D. Elevated levels of CAMP are synthesized

The lactose operon is not transcribed

70. Lactose utilization by E. coli regulates the gene which transports lactose into the cell. A. LacZ B. LacA C. LacY D. Lac

LacY

71. What would be the consequence if a mutation in lac causes its activation? A. Continuous expression of lacZ, lacy, Lac A genes B. Inability to transport lactose into cell C. Inability to form allolactose D. Inability to hydrolyze lactose

Continuous expression of lacZ, lacy, Lac A genes

72. The lactose repressor is encoded by the A. LacY B. Lacz C. LacA D. LacI

LacI

73. Thrombosis occurs when the endothelium lining the blood vessels is damaged or removed. Which among the following is not characteristic of the resulting red thrombus from this event? A. Predominantly composed of erythrocytes B. Consists primarily of platelets and fibrin C. It forms at the site of an injury or abnormal vessel wall, particularly in areas where blood flow is stagnant D. Seen mostly in venous areas

Consists primarily of platelets and fibrin

74. Disseminated fibrin deposits are mostly found in which vessels? A. Arteries B. Veins C. Very small blood vessels or capillaries D. All of the above

Very small blood vessels or capillaries

75. Which does NOT characterize white thrombi? A. Have a fast rate of formation B. Have a firm consistency C. Associated in arterial system of circulation D. Have a hard consistency

Have a fast rate of formation

76. This stage of hemostasis is considered to be the primary hemostatic mechanism. A. Vascular phase B. Platelet phase C. Coagulation phase D. Bleeding phase

E. Platelet phase

77. Which statement does NOT characterize the phases common to both hemostasis and thrombosis? A. Formation of a loose and permanent platelet aggregate at the site of injury B. Formation of a fibrin mesh that binds to the platelet aggregate, forming a more stable hemostatic plug or thrombus C. Partial dissolution of the hemostatic plug or thrombus by plasmin D. Complete dissolution of the hemostatic plug or thrombus by plasmin

E. Formation of a loose and permanent platelet aggregate at the site of injury

78. During the platelet phase of hemostasis, platelets adhere to collagen via specific receptors on the platelet surface. This process involves which of the following glycoprotein complexes? A. GPVI B. GPla-lla C. GPIb-IX-V D. All of the above

All of the above

79. During the platelet phase of hemostasis, adhesion and binding to collagen of which specific platelet glycoprotein complex receptors is mediated by von Willebrand factor? A. GPVI B. GPla-lla C. GPIb-IX-V D. All of the above

GPIb-IX-V

80. Which is not a feature of von Willebrand factor? A. Glues platelets to damaged endothelium B. Binds and protects Factor IX C. Is secreted by endothelial cells into the plasma D. None of the above

Binds and protects Factor IX

81. This is the most potent activator of platelets: A. Phospholipase A2 B. Thrombin C. Von Willebrand Factor D. Thromboxane A2

Thrombin

82. Endothelial cells in the walls of blood vessels make important contributions to the overall regulation of hemostasis and thrombosis. Which molecule synthesized by endothelial cells inhibits platelet adhesion and aggregation by elevating levels of cGMP? A. Prostacyclin B. ADPase C. Nitric oxide D. Thrombomodulin

Nitric oxide

83. Which of the following molecules from the endothelium inhibits platelet aggregation by increasing levels of cAMP. A. Prostacyclin B. ADPase C. Nitric oxide D. Thrombomodulin

Prostacyclin

84. Activation of which factor provides an important link between the intrinsic and extrinsic pathways in the coagulation cascade? A. Factor I B. Factor IV C. Factor V D. Factor X

Factor X

85. Which among the following is not a Vitamin K-dependent factor? A. Factor IX B. Factor I C. Factor VII D. Factor X

Factor I

86. Which laboratory test measures the intrinsic pathway? A. Partial thromboplastin time (aPTT or PT) B. Prothrombin time (PT) C. Thrombin time (TT) D. Bleeding time (BT)

Partial thromboplastin time (aPTT or PT)

87. This laboratory parameter is used to measure the effectiveness of oral anticoagulants such as warfarin. A. Partial thromboplastin time (aPTT or PTT) B. Prothrombin time (PT) C. Thrombin time (TT) D. Bleeding time (BT)

Prothrombin time (PT)

88. This protein involved in blood coagulation is a Thiol-dependent transglutaminase that is activated by thrombin and stabilizes fibrin clot by covalent cross-linking. A. Factor V B. Factor VII C. Factor VIII D. Factor XIII

Factor XIII

89. There are several hereditary bleeding disorders. The most common hereditary bleeding disorder is. A. Hemophilia A B. Hemophilia B C. Hemophilia C D. von Willebrand disease

von Willebrand disease

90. Which laboratory finding is not expected among Hemophilia Patients? A. Prolonged Partial Thromboplastin Time (PTT) B. Prolonged Bleeding Time C. Prolonged Prothrombin Time (PT) D. Normal platelet

Prolonged Prothrombin Time (PT)

91. Which statement is NOT true about Aspirin? A. It is an effective antiplatelet drug B. It acts by inhibiting production of Thromboxane A2 C. It also inhibits production of prostacyclin D. ALL are TRUE

ALL are TRUE

92. The final common pathway in the complementary system involves which of the following? A. The formation of the membrane attack complex B. Increased vasodilation & permeability of capillary beds C. Vasodilation & permeability of capillary beds D. All are true

The formation of the membrane attack complex

93. Statement descriptive of Vitamin K. A. Plays an essential role in preventing thrombosis B. Increases the coagulation time among newborn infants with hemorrhagic disease C. Can be found in high concentration in cow or breast milk D. Is synthesized by intestinal bacteria

Is synthesized by intestinal bacteria

94. This inhibits the Carboxylation of Vitamin K-Dependent of factors A. Coumarin Anticoagulants B. Vitamin K C. Heparin D. Protamine

Coumarin Anticoagulants

95. There are four naturally occurring thrombin inhibitors that exist in normal plasma. Which among these thrombin inhibitors is the most important since it which contributes approximately 75% of the activity? A. Antithrombin B. Alpha-2-Macroglobulin C. Heparin cofactor lI D. Alpha-1-antitrypsin

Antithrombin

96. Genetic disorders that lead to bleeding occur. Of these principal disorders is Hemophilia A which results from a deficiency of which coagulation factors? A. Factor VII B. Factor VIll C. Factor IX D. Factor X

Factor VIll

97. Deficiency of this substance results to the most common inherited bleeding disorder. A. Factor VII B. Factor VIlI C. von Willebrand factor D. Factor X

von Willebrand factor

98. Which does not occur during the classic pathway of the complement cascade? A. Ag-Ab complex activate C1 to form an esterase B. C4b2b complex is formed C. C3 molecules are cleaved into C3a and C3b,C3a D. C3 convertase C3bBb is formed

C3 convertase C3bBb is formed

99. Biologic effect of the complement system: A. Opsonization B. Chemotaxis C. Cytolysis D. All of the above

All of the above

100. Which protein does not comprise C1: A. C4b B. C1q C. C1r D. C1s

C4b