BIOCHEMISTRY NATIONAL BOARD EXAM REVIEW.doc

BIOCHEMISTRY NATIONAL BOARD EXAM REVIEW Larry D. Barnes Department of Biochemistry University of Texas Health Science Center at San Antonio June, 2004 Addendum, June 2005 (pg. 35) The following questions (1-243) are from nine National Dental Board Examinations in Biochemistry-Physiology from 1978-1998. 1998 is the latest board exam released by the American Dental Association. This compilation of questions is intended to show the format, the subject areas generally covered, and the general level of knowledge required. Answers with some commentary are given beginning on page 29. The addenum begins on page 35 followed by answers. BASIC CHEMISTRY 1. Which of the following characterizes exergonic reactions? A. B. C. D. E. 3.

Decreased entropy Increased enthalpy Decreased enthalpy Negative free energy change Positive free energy change

Atoms are isotopes of each other only if A. their nuclei contain the same number of neutrons. B. their atomic numbers are the same, but their mass numbers differ. C. their mass numbers are the same, but their atomic numbers differ. D. one is a beta emitter, but the other is an alpha emitter.

5. Which of the following characterizes an asymmetric carbon? A. A carbon atom with four identical groups attached to it. B. A carbon atom with four different groups attached to it. C. A carbon with at least one carboxyl and one amino group attached to it. D. A carbon atom that has two heavy groups on one side and two light groups on the other.

2. What thermodynamic parameter is a measure of randomness or disorder in a system? A. B. C. D. E.

Entropy Enthalpy Free energy Potential energy Activation energy

4. Which of the following substances is LEAST polar? A. B. C. D.

Ethanol Cholesterol Palmitic acid Glycocholic acid

6. Which of the following compounds does NOT contain a high-energy bond? A. B. C. D. E.

ATP Acetyl CoA UDP-glucose Glucose-6-phosphate Phosphoenolypyruvate

7. Which of the following solutions has an osmotic pressure different from all the others? A. B. C. D. E.

1 M glucose 1 M sodium chloride 1 M potassium nitrate 1 N lithium iodide 1 N hydrochloric acid

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BUFFERS and pH 8. The Henderson-Hasselbach equations shows that A. B. C. D.

dilution of a buffer increases its pH. pH = pka when an acid is 0.1 N pH = pka when an acid is half neutralized. pH is independent of the dissociation constant of the acid

10. If the pH becomes lower than the isoelectric point of a protein, then how will the protein respond in an electrophoretic system? It will A. B. C. D. E.

become denatured. migrate to the negative pole. migrate to the positive pole. remain stationary and unchanged. separate into its different monomeric forms.

12. All of the following function in buffer systems in the blood EXCEPT A. B. C. D. E.

NaCl. H2C03. NaHCO3. Na2HPO4. NaH2PO4.

9. Which of the following represents the pH of a solution that has 10-5 M concentration of OHion? A. B. C. D. E.

5 7 9 Determine only if the pKa is known. Determinable only if the base composition is known.

11. A physiologic buffer functions to A. regulate the partial pressure of venous carbon dioxide. B. carry fixed acid from the site of its elimination to the site of its production. C. transport carbon dioxide from the site of its production to the site of its elimination. D. minimize the increase in hydrogen ion concentration that accompanies cellular acid production. E. maximize the decrease in hydrogen ion concentration that accompanies alkali formation. 13. The buffer system most important in maintaining the physiological pH of plasma is A. B. C. D. E.

protein/proteinate acetic acid/acetate carbonic acid/bicarbonate phosphoric acid/phosphate hydroxybutyric acid/hydroxybutyrate

BICARBONATE/CO2 14. Neutralization of acids by saliva results mainly from which of the following salivary contents?

15. MOST of the CO2 in blood is combined as A. H2C03.

A. B. C. D. E.

Mucin Ammonia Carbonate Bicarbonate Amino acids

B. C. D. E.

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HCO 3. CH3 –COOH. carbonic acid carbaminohemoglobin.

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BICARBONATE/CO2 (Continued) 16. The bicarbonate buffer system of the blood is very efficient because A. bicarbonate is rapidly excreted by the kidneys. B. bicarbonate is able to be stored in the tissue. C. carbon dioxide is able to combine with hemoglobin D. carbon dioxide forms a stable combination with base. E. carbon dioxide is rapidly eliminated through the lungs.

17. The normal blood bicarbonate-carbonic acid ratio is 20:1. A patient with a 10:1 ratio is in A. B. C. D. E.

compensated alkalosis. compensated acidosis. uncompensated alkalosis. uncompensated acidosis. none of the above. This patient’s ratio is within normal limits.

18. Absence of which of the following blood enzymes drastically reduces blood CO2 carrying capacity? A. B. C. D. E.

Carbonic anhydrase Alkaline phosphatase Pyruvate carboxykinase Histidine decarboxylase Serum glutamic-oxaloacetate transaminase

PROTEINS 19. Removal of a molecule of water between the carboxyl group of one amino acid and the amino group of a second amino acid results in formation of a A. B. C. D. E.

zwitterion. polypeptide. peptide bond. hydrogen bond. glycosidic bond.

21. Denaturation usually destroys all of the following bonds in protein EXCEPT A. B. C. D.

hydrogen bonds. covalent bonds. hydrophobic bonds. electrostatic bonds.

20. Which of the following BEST explains why proteins are able to buffer physiologic solutions over a wide range of pH? A. They are macromolecules of high molecular weight. B. They contain many functional groups with differing pKs. C. They have unique tertiary structures that sequester hydrogen ions. D. They have peptide bonds that are resistant to hydrolysis. 22. Which of the following is the best method for determining the three-dimensional structure of protein? A. B. C. D. E.

Dialysis Electrophoresis X-ray diffraction Ultracentrifugation None of these

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PROTEINS (Continued) 23. The amino acid that contributes to the tertiary structure of a protein by causing a bend when it occurs in the primary sequence is A. B. C. D. E.

leucine. alanine. proline. tyrosine. aspartic acid.

24. A mucin is which of the following types of proteins? A. B. C. D. E.

Simple protein Phosphoprotein Chromoprotein. Nucleoprotein. Glycoprotein.

25. How will a protein respond in an electrophoretic system, should the pH become lower than the isoelectric point of the protein? A. B. C. D. E.

It will become denaturated. It will migrate to the negative pole. It will migrate to the positive pole. It will remain stationary and unchanged. It will separate into its different monomeric forms.

ENZYMES 26. Which of the following is true regarding enzymes? A. B. C. D.

Are not reusable Are needed in large amounts Catalyze endergonic reactions only Increase the energy of activation of the reaction E. Decrease the energy of activation of the reaction 28. The Km value of an enzyme is numerically equal to A. half the maximum velocity expressed in moles/liter. B. velocity of a reaction divided by substrate concentration. C. substrate concentration in moles/liter necessary to achieve half the maximum velocity of a reaction. D. maximum velocity divided by half the substrate concentration in moles necessary to achieve maximum velocity.

27. The optimum pH for an enzyme is the A. B. C. D.

isoelectric point of the enzyme. pH of most rapid reaction rate. pH at which the enzyme is most soluble. pH of most rapid denaturation of the enzyme

29. In the relationship between the concentrations of substrate and the rate of an enzyme catalyzed reaction, the existence of a limited value (Vmax) of the reaction rate is due primarily to the A. exhaustion of the substrate supply. B. saturation of the enzyme with substrate. C. inhibition of the enzyme by the reaction products. D. denaturation of the enzyme at higher substrate concentrations. E. balance between the increase in reaction rate with increasing substrate concentrations and accelerated destruction of the enzyme at higher substrate concentrations.

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ENZYMES (Continued) 30. If the presence of a specific compound, C, increases the Km for an enzyme-substrate reaction, which of the following would be true about that enzyme? A. C would be a competitive inhibitor of the enzyme. B. C would be a noncompetitive inhibitor of the enzyme. C. The velocity vs. [S] plot for the enzyme would be the same with or without C. D. With C present, the enzyme would convert substrate to product faster. E. With C present, it would take less substrate to drive the reaction to half-maximum velocity than without C. 32.

ATP inhibits phosphofructokinase even though ATP also is a substrate for the enzyme. Which of the following types of inhibition BEST explains this phenomenon? A. B. C. D. E.

Allosteric Competitive Irreversible Uncompetitive Noncompetitive

34. Sodium fluoride inhibits glycolysis by affecting A. B. C. D.

amylase enolase phosphatase phosphorylase

36. Two enzymes that have been postulated to play very important roles in calcification are A. B. C. D.

enolase and phosphorylase. alkaline phosphatase and catalase. pyrophosphatase and carbonic anhydrase. pyrophosphatase and alkaline phosphatase. E. carbonic anhydrase and alkaline phosphatase.

31. Protein kinase regulate the activities of key enzymes through which of the following? A. B. C. D. E.

Oxidation Hydrolysis Acetylation Phosphorylation Dephosphorylation

33. Enzymes for electron transport reactions are most active and concentrated in which of the following structures of the animal cell? A. B. C. D. E.

Nuclei Lysosomes Microsomes Mitochondria All of the above

35. Which of the following enzymes converts trypsinogen to trypsin? A. B. C. D.

Enterokinase Peptidase Secretin Pepsin

37. Which of the following enzymes is essentially absent from normal mammalian muscle? A. B. C. D. E.

Glucokinase Phosphorylase Glucose-6-phosphatase Glucose-6-phosphate isomerase Glucose-6-phosphate dehydrogenase

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ENZYMES (Continued) 38. Dental plaque arises primarily as a result of enzymatic reactions using which of the following? A. B. C. D.

Sucrose and lipid Sucrose and saliva Glucose and saliva Glucose and protein

39. Which of the following liver enzymes, absent from other tissues, gives the liver an advantage over other cells in taking up glucose after a meal? A. B. C. D. E.

Glucokinase Aldolase Hexokinase Enolase Glucose-6-phosphatase

COLLAGEN 40. The most abundant protein (by weight) in which the human body is A. B. C. D. E.

elastin. keratin. albumin. collagen. chondroitin.

42. Which of the following statements concerning collagen is INCORRECT?

41. Alpha-ketoglutarate, oxygen, and ascorbic acid are essential for which of the following processes? A. B. C. D. E.

Incorporation of proline Hydroxylation of proline Gamma-carboxylation of proline Oxidative deamination of lysine Activation of procollagen peptidase

43. Hydroxylation of proline and lysine during collagen biosynthesis occurs

A. Collagen has a trihelical structure. B. The molecular weight of collagen is above 100,000 C. Hydroxyproline is incorporated into the molecule by tRNA. D. Destruction of collagen can be caused by collagenases. E. Collagen contains both hydroxyproline and hydroxylysine residues.

A. after translation. B. in the mitochondrial matrix. C. before formation of their respective amino acyl-tRNA’s. D. while proline or lysine is bound to the peptidyl (P) site on the ribosome.

44. The major protein produced by the odontoblast and contained in the organic matrix of dentin is

45. Which of the following do elastin and collagen have in common?

A. B. C. D. E.

chitin. keratin. elastin. collagen. cellulose.

A. B. C. D. E.

Easily stretched Absence of proline Disulfide crosslinking Triple helix structure About one-third glycine

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HEMOGLOBIN 46. The physiologic importance of hemoglobin lies in its ability to combine A. irreversibly with oxygen and CO2. B. reversibly with oxygen at the ferric heme prosthetic group. C. irreversibly with oxygen at the ferrous heme prosthetic group. D. reversibly with oxygen at the ferrous heme prosthetic group. E. None of the above 48. Assuming that P50 = 26 torrs, under conditions where pO2 = 30 torrs, the average number of O2 molecules bound per hemoglobin molecule is closest to A. B. C. D. E.

0.5. less than 1. almost 2. greater than 2. greater than 3.

50. The consequence of appreciable conversion of hemoglobin to methemoglobin is A. a significant increase in carbon dioxide combining power. B. a significant decrease in carbon dioxide combining power. C. no effect on the ability of blood to pick up oxygen. D. a noticeable increase in the ability of blood to pick up oxygen. E. a noticeable decrease in the ability of blood to transport oxygen.

47. Which of the following is NOT a part of the hemoglobin molecule? A. B. C. D. E.

Iron Protein Magnesium Histidine Pyrrole ring

49. The affinity of hemoglobin for oxygen diminishes as which of the following is decreased? A. B. C. D. E.

pH CO2 Temperature Hydrogen ion concentration 2, 3 bisphosphoglyceric acid (BPG)

51. Compared with hemoglobin A, the substitution of a valine for a glutamic acid residue in hemoglobin S results from A. B. C. D.

a genetic mutation irradiation of hemoglobin A. proteolytic action in the liver. exposure to low oxygen tension.

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PROTEIN SYNTHESIS 52. The process by which genetic information flows from RNA to protein is A. B. C. D.

mutation. replication. translation. transcription.

54. Polyuridylic acid in a cell-free system capable of protein synthesis results in production of polyphenylalanine. In this system, polyuridylic acid functions as A. B. C. D. E.

DNA. transfer RNA. messenger RNA. ribosomal RNA. mitochondrial RNA.

56. In prokaryotic protein synthesis, the elongation factor G serves to A. form the initiation complex. B. facilitate the binding of Fmet tRNA. C. translocate the growing peptide chain and to move the ribosome along the mRNA. D. prevent the larger ribosomal subunits from binding with those that are smaller.

53. Which of the following enzymes or processes ensures that the correct amino acid is incorporated for a particular codon during protein synthesis? A. B. C. D. E.

Amino Acyl-tRNA synthetase Ribosomal protein synthesis Post-transcription splicing RNA synthetase Helicase

55. The termination of synthesis of a polypeptide is believed to involve A. B. C. D. E.

nonsense codons. anticodon-codon interaction. tRNA which cannot bind amino acids. hydrolysis of messenger RNA. none of the above.

57. Streptomycin is an antibiotic which inhibits the process of A. B. C. D. E.

translation in eukaryotes. translation in prokaryotes. transcription in eukaryotes. transcription in prokaryotes. DNA replication in prokaryotes.

58. Each of the following represents an amino acid found in proteins and used directly in the reactions of protein synthesis EXCEPT one. Which one is this EXCEPTION? A. B. C. D. E.

Proline Arginine Tryptophan Asparagine Hydroxylysine

CARBOHYDRATES 59. Hydrolysis of sucrose by the enzyme sucrase yields A. B. C. D. E.

glucose only. glucose and maltose. glucose and fructose. glucose and galactose. fructose and maltose.

60. The arrangement of sugars into D- and Lconfigurations is based upon their resemblance to D- and LA. B. C. D. E.

glycine. glucose. fructose. glyceraldehyde. None of the above

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CARBOHYDRATES (Continued) 61. Which of the following is NOT a monosaccharide? A. B. C. D. E.

Amylose Glucose Fructose Glyceraldehyde Glucuronic acid

63. What linkages occur in glycogen at branch points between glucose units? A. B. C. D. E.

Aplpha-1,4 Alpha-1,6 Beta-1,3 Beta-1,4 Beta-1,6

65. Carbohydrate is stored in the body principally as A. B. C. D. E.

glucose. maltose. sucrose. glycogen. glycosaminoglycans.

67. Which of the following functions as part of the extracellular matrix? A. B. C. D. E.

Mucin Heparin Collaginase Chondroitin sulfate Dolichol phosphate

69. Glycosaminoglycans function as important structural components of A. B. C. D.

glycogen. nucleic acids. hyaluronidase. connective tissue.

62. Some carbohydrates convert Cu2+ ions to Cu+ ions. This property is related to their ability to act as A. a reducing agent. B. an oxidizing agent. C. both a reducing agent and an oxidizing agent. D. neither a reducing agent nor an oxidizing agent. 64. How many anomeric carbons are present in a fructose molecule? A. B. C. D. E.

0 1 2 5 6

66. Which of the following molecule features contributes to the water-binding properties of proteoglycans? A. The carboxyl groups acting as buffers B. Central hyaluronate (a helix) trapping water within C. The space between the core proteins and the hyaluronate being highly charged. D. The large number of alcohol groups on the polysaccharide chaining H-bond to water. E. The large number of serine and theronine residues in the core protein offering Hbonding sites. 68. Each of the following is a glycosaminoglycan EXCEPT one. Which one is this EXCEPTION? A. B. C. D. E.

Chondroitin sulfate Dermatan sulfate Hyaluronic acid Heparan sulfate Keratin

70. The carbohydrate in highest concentration in resting muscle is A. B. C. D. E.

glucose. lactose. sucrose. glycogen. inositol.

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CARBOHYDRATES (Continued) 71. The most biologically important physiochemical property of connective tissue which is regulated by its mucopolysaccharide molecules is A. B. C. D.

viscosity. buffering capacity. solubility in dilute acides. supersaturation with calcium ions.

NUCLEIC ACIDS 72. Which of the following is a pyrimidine base that is present in RNA but is NOT present in DNA? A. B. C. D. E.

Uracil Guanine Thymine Adenine Cytosine

74. In the DNA molecule, guanine on 1 strand is joined to cytosine on the complementary strand by which of the following bonds? A. B. C. D. E.

Amide 1 hydrogen 2 hydrogen 3 hydrogen Phosphodiester

76. Which of the following are NOT produced by the hydrolysis of nucleic acids? A. B. C. D. E.

Pentoses Phosphates Amino acids Purine bases Pyrimidine bases

78. If the molar percentage of A (adenine) in a native DNA specimen is 22%, then what is the molar content of G (guanine)? A. B. C. D. E.

22% 28% 44% 56% 78%

73. Which of the following bonds link the monomeric units of nucleic acids? A. B. C. D. E.

Ionic Peptide Thioester Glycosidic Phosphodiester

75. As DNA is denatured, each of the following events take place EXCEPT one. Which event is this EXCEPTION? A. Total G-C content of total DNA increasing B. UV light absorption increasing C. Complementary strands becoming random coils D. Base stacking becoming disrupted E. Hydrogen bond breaking 77. The function of which of the following types of nucleic acid is to activate and select specific amino acids for protein synthesis? A. B. C. D. E.

rRNA mRNA cDNA tRNA hnRNA

79. The degenerate nature of the genetic code implies A. a common tRNA for at least two amino acids. B. that a remarkable degree of inaccuracy occurs in transcription. C. the existence of multiple codons for each amino acid. D. the existence of multiple species of ribosomes for control of messenger translation.

NUCLEIC ACIDS (Continued)

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80. Transcription is the cellular process of making A. B. C. D.

new DNA. RNA from DNA. proteins from amino acids by way of RNA. none of the above.

82. DNA damage by ultraviolet light is due to A. alkylation of the guanine in DNA. B. excessive unwinding of the DNA molecule C. frequent replacement in the DNA molecule of purines by pyrimidines. D. induction of dimerization by way of covalent bonds between adjacent thymine groups.

81. Which of the following is true of the Tm (melting temperature) of a given DNA double helix? A. Is a function of the base composition B. Can be used to accurately predict its molecular weight C. Can be measured by observing the change in chemical composition D. Is higher if individual strands of the DNA double helix are parallel rather than antiparallel 83. Each of the following is involved in gene cloning EXCEPT one. Which one is this EXCEPTION? A. B. C. D. E.

DNA ligase RNA polymerase DNA polymerase I Restriction nucleases Reverse transcriptase

84. Plasmid vectors suitable for cloning have which of the following characteristics?

85. The polymerase chain reaction is MOST useful for which of the following?

A. Must be able to replicate synchronously with the host chromosome B. Several unique recognition sequences for one restriction enzyme C. Two genes conferring resistance to different antibiotics D. Large size to facilitate plasmid’s entry into cells

A. Preparing enzymes that synthesize nucleic acids B. Isolating the genome of an organism C. Amplifying a specific DNA sequence D. Separating polyclonal antibodies E. Synthesizing RNA and DNA

LIPIDS 86. Which of the following is LEAST descriptive of lipids? A. B. C. D.

Nonpolar Carbon-containing Amphipathic Hydrophilic

88. Upon complete hydrogenation, oleic, linoleic and linolenic acids yield A. B. C. D. E.

stearic acid. myristic acid. palmitoleic acid. arachidonic acid. multiple acetate fragments.

87. Which of the following substances represents an unsaturated fatty acid? A. B. C. D. E.

Cholesterol Palmitate Stearate Choline Oleate

89. Which of the following classes of steroids contain 18 carbons and an aromatic ring? A. B. C. D. E.

Estrogens Androgens Progestagens Glucocorticoids Mineralocorticoids

LIPIDS (Continued)

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90. Gangliosides are glycolipids found on various cell surfaces. In addition to sphinogosine, their unit composition contains another characteristic component. This component is A. B. C. D. E.

uronic acid. plasmalogen. triglyceride. N-acetylmuramic acid. N-acetylneuraminic acid.

92. In addition to phosphoric acid, which of the following are the products of hydrolysis of lecithin? A. B. C. D. E.

Glycerol, fatty acids, serine Glycerol, fatty acids, choline Sphingosine, acetic acid, inositol Glyceraldehyde, fatty acids, choline Glyceraldehyde, fatty acids, ethanolamine

94. Carbon dioxide or bicarbonate is required in the biosynthesis of fatty acids because A. the bicarbonate/carbonic acid buffer system is very efficient at the pH optimum of this sensitive enzyme system. B. bicarbonate is a positive effector for this system and favorably alters the conformation of its enzymes. C. carbon dioxide is incorporated into acetyl coenzyme A forming malonyl coenzyme A, an intermediate in the synthetic process. D. carbon dioxide is incorporated into carbamyl phosphate, a reactive intermediate in the synthetic process. E. carbon dioxide provides an anaerobic environment that prevents oxidation of the sulfhydryl groups in the reactive sites of the enzyme system. 96. The pathway of extramitochondrial synthesis of even-numbered fatty acids differs from that of the catabolism of fatty acids in that A. malonyl CoA is an intermediate in synthesis. B. acyl carrier protein is needed in catabolism. C. no flavoprotein enzymes are required for catabolism. D. propionyl CoA may serve as an intermediate in synthesis.

91. Neutral fats contain mixtures of one or more fatty acids esterified with A. B. C. D. E.

sterol. glycerol. lecithin. sphinogosine. alcohols of high molecular weight.

93. Which of the following is an essential fatty acid? A. B. C. D. E.

Acetic Stearic Myristic Palmitic Arachidonic

95. The enzyme catalyzing the rate-controlling step in the de novo synthesis of fatty acids is regulated allosterically by the positive modulator A. B. C. D. E.

ATP. NADPH. Citrate. cyclic AMP. oxaloacetate.

97. Beta oxidation of a mole of an 18 carbon fatty acid under physiologic conditions produces A. B. C. D. E.

one mole of acetic acid. nine moles of acetyl CoA. nine moles of acetic acid. one mole of acetoacetic acid. one mole of hydroxybutyric acid.

LIPIDS (Continued)

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98. Sodium taurocholate and glycocholate are necessary for the absorption of A. B. C. D. E.

sucrose. glycerol. amino acids. fatty acids. nucleic acids.

100. Which of the following is MOST often associated with free fatty acid transport in human blood? A. B. C. D. E. 102.

Albumin Globulin Cholesterol Sphingolipid Mucopolysaccharide

99. After functioning in the small intestines, the largest portion of bile salts are A. excreted in the feces. B. reabsorbed into the central lacteal. C. destroyed by bacteria in the large intestines. D. reabsorbed into the portal circulation and reused. E. removed from the circulation by the kidneys and excreted in the urine. 101. Triglyceride absorbed into the lymphatic system is transported to the liver as which of the following? A. B. C. D. E.

Very low density lipoprotein Low density lipoprotein Chylomicrons Liposomes Micelles

Which of the following compounds is an intermediate in the biosynthesis of cholesterol? A. B. C. D. E.

Squalene Hexosamine Cholic acid Pregnanediol Deoxycholic acid

MEMBRANES 103. The major lipids that make up the cell membrane are A. B. C. D. E.

triglycerides. sphingomyelins. phospholipids. fatty acids. steroids.

105. Each of the following lipid classes is incorporated into membranes EXCEPT one. Which one is this EXCEPTION? A. B. C. D. E.

Cholesterol Ganglioside Triglyceride Sphingomyelin Phosphatidylcholine

104. The most abundant nonphospholipid component of the cell membrane is A. B. C. D. E.

cholesterol. deoxycholate. prostaglandin. macroglobulin. triacylglyceride.

106. Which of the following represents a polyunsaturated fatty acid that is commonly found in animal cell membranes? A. B. C. D. E.

Oleic Lactic Sialic Stearic Linoleic

MEMBRANES (Continued)

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107. The fluid-mosaic model for membrane structure proposes that A. the outer and inner faces of the membrane are identical. B. peripheral proteins are situated only on the outer face of the plasma membrane. C. integral proteins are associated with the hydrophobic phase of the bilayer. D. both polar and nonpolar ends of membrane phospholipids are within the hydrophobic phase of the bilayer. 109. Which of the following molecules would likely form a micelle when mixed with water and agitated? A. B. C. D.

Serine Glycerol Phospholipid Triglyceride

111. Mediated (facilitated) diffusion of substances across cell membranes differs from simple diffusion in that mediated diffusion A. B. C. D.

requires ATP. requires another solute. is a one-directional process. exhibits saturation kinetics.

108. The major driving force for formation of a lipid micelle is A. protein-lipid interaction. B. hydrophobic interaction between hydrocarbon tails. C. hydrogen bonding between water molecules of the micellar core. D. electrostatic interaction between the micellar core and polar heads.

110. The rapid movement of a substance across a biologic membrane against a concentration gradient requires A. that the substance be negatively charged. B. participation of an energy-requiring active transport system. C. that the substance be readily soluble in the lipid barrier of the membrane. D. that the substance be carried across the membrane by rapid influx of the solvent. E. facilitated diffusion of the substance aided by some binding system in the membrane 112. Which of the following features distinguishes active transport from facilitated diffusion? A. B. C. D.

Specificity Carrier-mediated Requires metabolic energy Presence of a transport maximum (Tm)

METABOLISM 113. Reactions that have unfavorable energetics (i.e., + ∆G0) in metabolic pathways may be driven to completion by which of the following processes? A. B. C. D.

Coupling Allosterism Modification Microscopic reversibility

114. A common intermediate of metabolism of carbohydrates, fatty acids and amino acids is A. B. C. D. E.

glycerol. acetyl CoA. acetoacetate. oxaloacetate. acetylcholine.

METABOLISM (Continued)

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115. A number of catabolic pathways are allosterically inhibited by an increase in the concentration of which of the following? A. B. C. D. E.

ADP AMP ATP NAD+ Pyruvate

117. Under strict anaerobic conditions, the catabolism of one glucose molecule would yield a net of A. B. C. D.

2 ATP and 2 lactic acid molecules. 4 ATP and 2 lactic acid molecules. 2 ATP and 2 pyruvic acid molecules. 4 ATP and 2 pyruvic acid molecules.

119. Enzymes that catalyze the anaerobic processes of carbohydrate metabolism are found predominantly in which part of a cell? A. B. C. D. E.

Cytoplasm Membrane Cell wall Nucleus Mitochondria

121. Consider the conversion: alanine – lactic acid – glucose. This is an example of A. B. C. D.

glycolysis. glycogenolysis. gluconeogenesis. synthesis of glycerol.

116. In the glycolytic sequence, the enzyme that brings about the transition from 6-carbon metabolites to 3-carbon metabolites is A. B. C. D. E.

phosphoglucoisomerase. phosphofructokinase. phosphorylase. hexokinase. aldolase.

118. Muscle glycogen does not yield blood glucose directly but liver glycogen does because A. hexokinase is not present in liver. B. muscle cells are impermeable to glucose. C. muscle does not contain phosphoglucomutase. D. muscle glycogen differs in structure from liver glycogen. E. glucose-6-phosphatase is not present in muscle. 120. Cyclic 3’, 5’-AMP increases the rate of glycogenolysis by A. promoting the formation of a phosphorylated form of glycogen phosphorylase. B. serving as a substrate for glycogen phosphorylase. C. serving as a precursor of 5’ AMP which is a cofactor for glycogen phosphorylase. D. furnishing phosphate for the phosphorolysis of glycogen. 122. Energy for ATP synthesis is derived from the electron transport system by which of the following processes? A. B. C. D. E.

Transamination Aldolization Reductive synthesis Oxidative deamination Oxidative phosphorylation

METABOLISM (Continued)

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123. The chemical energy generated by mitochondrial electron transport results from which of the following? A. Excess H+ in the matrix B. An H+ gradient across the inner membrane C. The formation of thioesters in the matrix D. A conformational change in the inner membrane

125. Which of the following represents the chemical substance that is the immediate source of energy for muscle contraction? A. B. C. D. E.

Glycogen Acetyl CoA Lactic acid Creatine phosphate Adenosine triphosphate

127. Enzymes concerned with the citric acid cycle are found in the A. B. C. D. E.

nucleus. ribosomes. mitochondria. nonparticulate cytoplasm. None of the above

129. If protein is catabolized for energy, then MOST of the energy is derived from which of the following? A. B. C. D. E.

Urea production Oxidative deamination Transamination reactions Cleavage of peptide bonds Oxidation of α-keto acids derived from amino acids.

124. Functions of the hexose monophosphate shunt include the production of (1) NADP for lactate oxidation. (2) NADPH for fatty acid synthesis. (3) glucuronic acid for heparin synthesis. (4) D-ribose for nucleic acid synthesis. (5) ATP for anaerobic muscle contraction. A. B. C. D. E.

(1), (3), and (5) (1) and (4) (2), (3), and (5) (2) and (4) (3) only

126. The tricarboxylic acid cycle is initiated by the condensation of which of the following two molecules? A. B. C. D. E.

Pyruvate and malate NAD+ and oxaloacetate NAD+ and oxalosuccinate Acetyl coenzyme A and oxaloacetate Acetyl coenzyme A and oxalosuccinate

128. Acids found in the citric acid (Krebs) cycle are A. B. C. D. E.

glutamic acid and succinic acid. glucuronic acid and aspartic acid. oxaloacetic acid and aspartic acid. oxaloacetic acid and pyruvic acid. oxaloacetic acid and α-ketoglutaric acid.

130. Which of the following is the FIRST step in the catabolism of many amino acids? A. Formation of a dipeptide with glutamate B. Conjugation of the alpha amino to glucuronate C. Transamination of the alpha amino to a keto acid D. Conjugation of the alpha carboxyl group to glucuronate E. Decarboxylation of the alpha carboxyl group to form a primary amine

METABOLISM (Continued)

16

131. Which of the following statements is NOT true about ammonia and the α-amino group of amino acids? A. NH+4 is formed from glutamine in the kidney. B. The amino group in carbamyl phosphate is directly donated by aspartate in a transamination reaction. C. Cellular levels of ammonia must be maintained at low concentrations because of its toxicity. D. Glutamate dehydrogenase can catalyze the formation of glutamate from ammonia and α-ketoglutarate using NADPH as a cofactor. 133. What is the product P in the following reaction? α-ketoglutarate + alanine = pyruvate + P A. B. C. D. E.

Glutamate Glutamine Aspartate Succinate Pyridoxine phosphate

135. After prolonged acidosis, which of the following represents the nitrogenous product that is excreted in high amounts in the urine? A. B. C. D. E.

Urea Ammonia Uric acid Creatinine Aspartic acid

137. In relative insulin insufficiency, acetyl CoA is usually channeled into A. B. C. D. E.

ketone-body formation. cholesterol synthesis. fatty-acid synthesis. gluconeogenesis. the Krebs cycle

132. The level of nonprotein nitrogen in the blood is due principally to the level of which of the following? A. B. C. D. E.

Urea Ammonia Creatine Arginine Uric acid

134. Which of the following tissues is primarily responsible for formation of urea? A. B. C. D.

Liver Brain Kidney Muscle

136. Excessive utilization of fats by the body as a source of energy during disturbances in carbohydrate metabolism can lead to all of the following conditions EXCEPT A. B. C. D.

ketosis. acidosis. ketonuria. alkalosis.

138. The ketone body acetoacetate is synthesized inside mitochondria of hepatocytes by A. carboxylation of pyruvic acid. B. transamination of aspartic acid. C. cleavage of β-hydroxy- β-methylglutaryl CoA. D. oxidative decarboxylation of αketoglutarate. E. oxidation of L-β-hydroxybutyrate followed by deacylation.

METABOLISM (Continued)

17

139. The final step in the complete metabolism of fat is carried out by means of A. B. C. D. E.

anaerobic glycolysis. the tricarboxylic acid cycle. the reductive fixation of CO2. the hexose monophosphate shunt. the Krebs-Henseleit (urea) cycle.

141. How do inadequate insulin levels, such as those which occur in diabetes mellitus, affect fat metabolism? A. Glucose utilization is increased. B. Utilization of fat for energy is increased. C. Storage of cholesterol by the Kupffer cells is increased. D. Level of beta-hydroxybutyric acid in the urine is depressed. 143. The metabolite, 25-hydroxycholecalciferol is derived MOST immediately from A. B. C. D. E.

ergosterol. cholesterol. 7-dehydro-sitosterol. 7-dehydro-cholesterol. 22-dihydro-ergosterol.

145. Most endogenous cholesterol in the liver is usually converted into which of the following? A. B. C. D. E.

Glucose Steroids Cholic acid Oxaloacetate Ketone bodies

147. Purine ribonucleoside phosphates are all synthesized de novo from the common intermediate A. B. C. D. E.

inosine phosphate. guanosine phosphate. adenosine phosphate. guanosine diphosphate. deoxyadenosine phosphate.

140. Mobilization of fat stored in adipocytes involves A. activation of fatty acids by synthesis of acyl CoA. B. rearrangement of fatty acids in triglycerides. C. phosphorylation of glycerol at the expense of ATP. D. activation of triglyceride lipase by ADP. E. activation of triglyceride lipase by a cAMP dependent protein kinase. 142. Prostaglandins are made within cells A. B. C. D. E.

on an RNA template. on rough endoplasmic reticulum. from methionine. from progesterone. from polyunsaturated fatty acids.

144. Which of the following is necessary for de novo synthesis of cholesterol? A. B. C. D. E.

NAD+ NADH NADP+ NADPH FADH2

146. Ribose phosphate needed for nucleic acid synthesis can be derived from A. B. C. D. E.

gluconeogenesis. the pentose phosphate pathway. the Krebs’ tricarboxylic acid cycle. decarboxylation of aromatic amino acids. one-carbon transfer from tetrahydrofolate derivatives.

148. Which of the following enzymes catalyzes the formation of uric acid from purines? A. B. C. D. E.

Urease Uricase Xanthine oxidase Aspartate transcarbamoylase Carbamoyl-phosphate synthetase

METABOLISM (Continued)

18

149. Which of the following is a source of transferable methyl groups in metabolism? A. B. C. D.

Valine Choline Leucine Isoleucine

151. Tay-Sach disease is associated with an inborn error of metabolism involving a specific enzyme which normally degrades a particular molecule in the gray matter. This enzyme acts on which of the following? A. B. C. D. E.

Polysaccharides Acylglycerols Gangliosides Fatty acids Proteins

150. Coenzyme A participates in A. B. C. D.

formylation. protein synthesis. methionine activation. activation of carboxyl groups.

152. Glucosuria with hyperglycemia usually occurs in which of the following? A. B. C. D. E.

Pellagra Addison’s disease Diabetes mellitus Diabetes insipidus Parkinson’s disease

VITAMINS 153. Which of the following is a vitamin? A. B. C. D. E.

Adenine Inosine Xanthine Thyroxin Pyridoxine

155. Pantothenic acid is an integral part of A. B. C. D. E.

NAD+. cobalamin. folic acid. coenzyme A. pyridoxine phosphate.

157. A vitamin derivative concerned with conversion of glucose to lactic acid is A. B. C. D.

thiamine (as cocarboxylase). pantothenic acid (as coenzyme A). pyridoxal (as pyridoxal phosphate). nicotinamide (as nicotinamide adenine dinucleotide).

154. The general reaction for the transfer of a “onecarbon fragment” requires the coenzyme A. B. C. D. E.

pyridoxal phosphate. tetrahydrofolic acid. thiamine pyrophosphate. flavin adenine dinucleotide. diphosphopyridine nucleotide.

156. Derivatives of riboflavin and niacin function as A. B. C. D.

CO2 acceptors coenzymes in redox reactions. factors in transamination reactions. replacements for each other in biologic reactions.

158. Which of the following vitamins is necessary as a coenzyme in the initial steps of fatty acid synthesis? A. B. C. D. E.

Biotin Thiamine Vitamin A Vitamin D Riboflavin

VITAMINS (Continued)

19

159. Which of the following is required for vitamin D3 synthesis? A. B. C. D.

Decarboxylation in the liver UV activation of precursors in skin Metabolism by gut bacteria Deamination in the kidney

161. Vitamin A functions to A. B. C. D.

prevent pellagra. promote absorption of calcium. promote differentiation of epithelial cells. maintain the integrity of connective tissues.

163. The effect of a vitamin C deficiency on the developing tooth is primarily on the calcification of dentin and cementum. This can best be explained by which of the following statements? A. This does happen, but the reason is obscure. B. Dentin is the most sensitive tissue in the body to a vitamin C deficiency. C. Vitamin C influences the formation of collagen, the organic matrix found in dentin and cementum. D. Vitamin C has metabolic interrelations with other vitamins that have a greater influence on dentin and cementum than on enamel. E. The vascular system is more important to these tissues than to enamel and, in an avitaminosis C, the vascular system is subject to hemorrhage. 165. Which of the following is NOT involved as a cofactor in formation of acetyl CoA from pyruvate? A. B. C. D. E.

NAD+ FAD Pyridoxine Lipoic acid Thiamine pyrophosphate

160. Hydroxylation at the 1 position of 25hydroxycholecalciferol occurs primarily in the A. B. C. D.

skin. liver. kidney. intestinal mucosa.

162. A deficiency of vitamin A in a developing tooth most likely affects the A. B. C. D.

pulp. enamel. dentin. cementum.

164. Which of the following is a function of vitamin B6 (pyrodoxal phosphate)? A. Prevents pernicious anemia B. Allows adaptation to dim light C. Acts as coenzyme in transamination reaction D. Prevents microcytic hypochromic anemia

166. A derivative of vitamin K is the coenzyme for which of the following? A. B. C. D. E.

Production of menadiol Esterfication of retinol Hydrolysis of peptide bonds Cross-linking of fibrinogen Carboxylation of glutamate side chains

VITAMINS (Continued)

20

167. The function of vitamin K is involved directly with A. B. C. D. E.

synthesis of prothrombin. activation of the Stuart factor. regulation of calcium in the blood. conversion of fibrinogen to fibrin. transcriptional control for fibrinogen synthesis.

169. Osteoblasts form the organic matrix of bone prior to calcification of the tissue. This process requires vitamins A. B. C. D. E.

A and B12. A and C. A and D. C and E. D and E.

168. Which of the following vitamins can be supplied to humans by the normal action of intestinal flora? A. B. C. D. E.

A D E K None of the above

170. To which of the following avitaminoses is the gingival most susceptible? A. B. C. D. E.

A B2 B6 C Niacin

NUTRITION 171. Some amino acids need not be present in the diet of an animal because of the animal’s ability to synthesize the acids at an adequate rate. A principal source of carbon for these amino acids is A. B. C. D.

nucleic acids. carbon dioxide. metabolism of carbohydrates. methylene folic acid derivatives.

173. Which of the following groups includes only amino acids essential for humans? A. B. C. D. E.

Valine, serine, leucine Leucine, lysine, glycine Tyrosine, threonine, tryptophan Phenylalanine, methionine, proline Tryptophan, methionine, isoleucine

175. A diet rich in tryptophan offsets a deficiency of which of the following vitamins? A. B. C. D.

Niacin Thiamine Riboflavin None of the above

172. Negative nitrogen balance (nitrogen excretion > intake) may be cause by A. B. C. D.

growth. protein synthesis. dietary lack of essential amino acid. synthesis and catabolism of equal amounts of body protein.

174. Which of the following amino acids lessens the need for phenylalanine? A. B. C. D. E.

Lysine Leucine Glycine Tyrosine Tryptophan

176. A deficiency of rhodopsin is most likely caused by decreased dietary intake of A. B. C. D. E.

glucose. adenine. vitamin A. tryptophan. riboflavin.

NUTRITION (Continued)

21

177. Lipid is required in the average diet because it A. B. C. D.

has a high caloric value. provides essential fatty acids. aids in absorption of carbohydrates. is necessary for storage of carbohydrates.

179. Purine bases taken in the human diet in the form of DNA or RNA are mostly A. excreted as urea. B. excreted in the form of uric acid. C. reused and converted to ATP needed as a source of energy. D. broken down to give NH3 and either malonic acid or methylmalonic acid. 181. Which of the following represents the amount of dietary calcium normally absorbed from the gut of an adult man? A. B. C. D.

An amount less than 50% An amount between 60-70% An amount between 80-100% An amount dependent up the mucosal ferritin level

183. The recommended daily dietary allowances for Ca and P provide a Ca/P intake of approximately A. B. C. D. E.

0.5. 1.0 2.0. 3.0. 4.0.

185. Which of the following is secreted more during the absorptive state than during the postabsorptive state? A. B. C. D. E.

Insulin Glucagon Cortisol Thyroxine Ephinephrine

178. A deficiency of choline in the diet can cause abnormalities in the metabolism of A. B. C. D. E.

lipids. proteins. minerals. carbohydrates. nucleoproteins.

180. Which of the following minerals are most frequently in short supply in American diet? A. B. C. D.

Calcium and iron Calcium and iodine Sulfur and potassium Iodine, magnesium and iron

182. A diet deficient in calcium will result in A. stimulation of the thyroid gland. B. increased ability to cross-link fibrin. C. production of calcitonin and a low blood calcium level. D. production of parathyroid hormone and bone resorption. 184. Which of the following must be digested before being in a form that can be absorbed by enterocytes? A. B. C. D. E.

Monoglycerides Fatty acids Fructose Glycine Maltose

186. A sustained, severe carbohydrate deficiency in the diet will result in which of the following? A. B. C. D.

Ketoacidosis Severe metabolic alkalosis A deficiency in prostaglandin formation An inability to synthesize ascorbic acid

HORMONES

22

187. Which of the following hormones is a polypeptide? A. B. C. D. E.

Epinephrine Testosterone Progesterone Triiodotyronine Follicle-stimulating hormone

189. Which of the following hormones is NOT synthesized from cholesterol? A. B. C. D. E.

Progesterone Testosterone Estradiol Cortisol Relaxin

191. Each of the following characterizes a peptide hormone EXCEPT one. Which one is this EXCEPTION? A. B. C. D. E.

Stored in secretory granules Synthesized in a precursor form Binds to intracellular receptors Acts by generating a second messenger Usually transported unbound in plasma

193. The intracellular, “second” messenger for many peptide and polypeptide hormones is A. B. C. D. E.

AMP. ATP. cyclic AMP. adenylate cyclase. a cytoplasmic receptor.

195. The hyperglycemic effect of glucagon is mediated primarily through A. B. C. D. E.

the growth hormone. muscle glycolysis. liver glycogenolysis. inhibition of cortisol action. enhanced glucose reabsorption by renal tubules.

197. Which of the following takes place as proinsulin is converted to insulin? A. B. C. D.

Disulfide bonds are formed. Disulfide bonds are broken. The polypeptide chain is lengthened. A segment of the polypeptide chain is removed.

188. Iodine is primarily important in the biochemical synthesis of A. B. C. D. E.

ACTH. thyroxin. adrenalin. calcitonin. parathyroid hormone.

190. In which of the following combinations is the name of the hormone, its chemical type and its tissue of origin correctly matched? A. B. C. D. E.

Aldosterone-peptide-pancreas Glucagon-peptide-adrenal cortex Epinephrine-steroid-adrenal medulla ACTH-polypeptide-adrenal cortex Vasopressin-peptide-posterior pituitary

192. Which of the following generates a slowly developing long-term response in target tissues by binding to an intracellular receptor? A. B. C. D. E.

Glucagon Estrogen Prolactin Growth hormone Parathyroid hormone

194. Epinephrine causes an elevation in cAMP levels in muscle cells which in turn activate A. B. C. D. E.

ATPase. adenyl cyclase. glycogen synthetase. glycogen phosphorylase. glycogen phosphorylase phosphatase.

196. Two hormones which act similarly to increase glycogen and lipid breakdown as well as cyclic AMP synthesis are A. B. C. D.

insulin and calcitonin. glucagon and epinephrine. aldosterone and testosterone. parathyroid hormone and glucagon.

198. Which of the following hormones does NOT induce activation of adenylate cyclase? A. B. C. D.

Insulin Glucagon Epinephrine Parathyroid hormone

23

HORMONES (Continued) 199. Inhibition of lipolysis, stimulation of protein synthesis and increased entry of glucose into muscles and adipose tissues are biologic actions of the hormone A. B. C. D. E.

insulin. cortisol. glucagons. epinephrine. testosterone.

201. Aldosterone is normally associated with partial regulation of which of the following processes? A. B. C. D. E.

Sodium balance Gluconeogenesis Lipid digestion Protein degradation Carbohydrate metabolism

203. The parathyroid hormone acts in the body by A. decreasing absorption of calcium in the intestinal tract. B. accelerating the removal of calcium and phosphate from the skeleton but not from the teeth. C. stimulating gluconeogenesis in the liver. D. decreasing the excretion of sodium and chloride. E. All of the above

205. Hyperparathyroidism is marked by A. B. C. D. E.

chronic tetany. a high blood calcium level. retention of phosphates by the kidneys. storage of excess minerals in the bones. increased irritability of excitable tissues.

200. Which of the following is a principal action of insulin? A. B. C. D.

To mobilize lipid deposits To enhance cell permeability to glucose To decrease cell permeability to glucose To conserve glucose by breaking down amino acids

202. Which of the following BEST explains the primary action of antidiuretic hormone? A. It decreases the activity of the Na-K pump in the distal tubule. B. It increases the H2O permeability of the collecting ducts and the distal tubules. C. It decreases the pore size of the distal tubules and the collecting ducts. D. It decreases the glomerular filtration rate. E. It inhibits the action of glutaminase. 204. Each of the following is an effect of parathyroid hormone EXCEPT one. Which one is this EXCEPTION? A. Stimulation of 1-alpha-hydroxylase in kidney B. Stimulation of osteoclastic activity in bone C. Stimulation of calcium reabsorption by kidney D. Inhibition of phosphate reabsorption by kidney E. Inhibition of intestinal absorption of calcium 206. The low serum phosphate level in hyperparathyroidism is caused by A. increased renal loss of phosphate. B. decreased absorption of phosphate. C. increased deposition of calcium phosphate in bone. D. increased reabsorption of calcium phosphate from bone.

HORMONES (Continued)

24

207. A parathyroidectomized animal will exhibit which levels of calcium and phosphate ion concentration in the plasma? Calcium A. B. C. D. E.

Phosphate ion concentration

Low Normal High Normal Low

High Low Low Normal Low

209. Hydrolysis of thyroglobulin liberates a number of iodinated compounds. Two are considered thyroid hormones. These are A. B. C. D.

tyrosine and thyronine. tyrosine and diiodotyrosine. thyroxin and triiodothyronine. thyroxin and triiodotyrosine.

211. Which of the following describes the principal mechanism by which glucocorticoids stimulate their target cells? A. They activate specific genes. B. They activate initiation factors for protein synthesis. C. They increase the intracellular Ca++ concentration. D. They allosterically modify adenylate cyclase activity. E. They bind to cell membrane receptors and activate adenylate cyclase. 213. The gallbladder is caused to contract by the hormone A. B. C. D. E.

gastrin. secretin. pancreozymin. enterogastrone. cholecystokinin.

208. Which of the following are the immediate effects of calcitonin on serum levels of calcium and phosphate? Serum calcium A. B. C. D. E.

Increased Increased Decreased No change Decreased

Serum phosphate Increased Decreased Decreased Increased No change

210. Thyroid hormones, glucocorticoids and gonadal steroids are similar in that each A. B. C. D.

is derived from cholesterol. is derived from amino acids. acts on only one target organ or tissue. is released in response to signals from the hypothalamic-anterior pituitary complex. E. is released in response to signals from the hypothalamic-posterior pituitary complex. 212. The physiologically active form of vitamin D produced in the kidney is A. B. C. D. E.

1,25-dihydroxycholecalciferol. 25-hydroxycholecalciferol. 7-dehydrocholesterol. cholecalciferol. ergosterol.

214. Secretin functions in digestion of proteins by increasing A. B. C. D.

flow of bile. secretion of pepsin. flow of pancreatic juice. secretion of carboxypeptidase.

215. Androgens are produced in the testis and A. adrenal cortex. B. thyroid. C. adrenal medulla. D. pituitary. E. hypothalamus. FLUORIDE

25

216. The mechanism of systemic fluoride action in reducing dental decay is most likely the result of A. an increase in hardness of the tooth. B. an inhibition of proteolytic enzymes. C. deposition of CaF2 in areas of enamel susceptible to bacterial penetration. D. an increase in carbohydrate metabolism in the oral cavity as a result of enzyme inhibition. E. a reduction in rate of solubilization of enamel as fluoride content of the tissue increases. 218. Which of the following statements is NOT true concerning fluoride? A. B. C. D.

It is expected rapidly by the kidney. It is deposited in calcified tissues. It occurs only in the ionic form in plasma. It passes the placental barrier relatively slowly. E. At 1 ppm. In water, it is tasteless, odorless and colorless. 220. The rate of fluoride incorporation into bone depends upon the A. B. C. D. E.

water-mineral ratio. age of the individual. rate of bone remodeling or turnover. amount of ionizable fluoride in the diet. All of the above

217. Fluoroapatite can form during hard tissue formation by a (an) A. substitution of OH ions by F ions. B. reaction between CaF2 and CaHPO4. C. reaction of F ions with hydroxylysine residues. D. absorption of F ions onto hydroxyapatite crystal surfaces.

219. The anticaries effect of fluoride is LEAST related to which of the following? A. B. C. D. E.

Ion exchange Decreased solubility Facilitation of remineralization Its presence during enamel formation Activation of plaque polysaccharide hydrolysis

221. Sodium fluoride inhibits glycolysis by affecting which of the following? A. B. C. D.

Amylase Enolase Phosphatase Phosphorylase

BLOOD CLOTTING 222.

A deficiency in vitamin K would affect blood clotting chiefly by A. decreasing prothrombin production. B. preventing the contraction of the clot. C. preventing the reaction of thrombin with fibrinogen. D. preventing the conversion of fibrinogen to fibrin. E. preventing the conversion of prothrombin to thrombin.

223. Platelets play an important role in hemostasis. Which of the following describes this role? A. They convert fibrinogen to fibrin. B. They agglutinate and plug small, ruptured vessels. C. They initiate fibrinolysis in thrombosis. D. They supply fibrin stabilizing factor. E. They supply proconvertin for thromboplastin activation.

BLOOD CLOTTING (Continued)

26

224. Administration of heparin to a human results in symptoms similar to vitamin K deficiency in that both conditions result in A. release of lipoprotein lipase to the blood and rapid clearance of chylomicrons. B. and increase in bleeding time due to lack of thrombin formation. C. retardation of fibrinogen synthesis by the liver. D. elevated non-esterified fatty acids which chelate serum calcium, thus retarding blood clotting. 226. Which of the following represents the normal substrate of thrombin? A. B. C. D. E.

Fibrin Thrombospondin Prothrombin Thromboplastin Fibrinogen

225. Which of the following compounds is NOT involved in coagulation of blood? A. B. C. D. E.

Fe+2 Ca+2 Prothrombin Fibrinogen Thromboplastin

227. Which of the following ions is involved in blood clotting? A. B. C. D.

Iron Sodium Calcium Potassium

BONES AND TEETH 228. The organic matrix of bone is composed largely of collagen and A. B. C. D.

lipids. citrate. dextrans. glycosaminoglycans.

230. Which of the following explains why enamel is harder than bone? A. Enamel crystals are larger and more firmly packed. B. Enamel contains amelogenins in its organic matrix. C. Enamel contains more magnesium and carbonate. D. Enamel crystals have more surface area. E. Enamel contains more collagen. 232. Which of the following noncollagenous protein components BEST characterizes dentin matrix? A. Laminin B. Vimentin C. Phosphophoryn D. Osteonectin E. Fibronectin BONES AND TEETH (Continued)

229. Which of the following represent(s) the matrix proteins of enamel? A. B. C. D. E.

Carboxylglutamic acid containing proteins Type I collagen Amelogenins Proteoglycans Elastin

231. Which of following is the major protein component of cementum? A. B. C. D. E.

Elastin Keratin Collagen Amelogenin Osteonectin

233. Which of the following has a high affinity for binding calcium and collagen in the calcifying matrix? A. B. C. D. E.

Calcitonin Osteogenin Osteonectin Amelogenin Fibronectin

27

234. Protein content of enamel from mature teeth is approximately what per cent of enamel weight? A. B. C. D. E.

0.1-1% 5-10% 15-20% 25-30% 50-55%

236. Which of the following BEST characterizes hydroxyapatite? A. Has an amphiphilic surface B. Contains 12 ions per unit cell C. As found in bone and enamel contains no ion substitutions D. Has a higher solubility product constant than fluoroapatite 238. Which of the following vitamins is the LEAST likely to be involved in tooth development and calcification? A. B. C. D.

A B1 C D

240. The primary effect of calcitonin is to A. increase bone resorption. B. inhibit bone resorption. C. increase calcium absorption from the intestine. D. decrease calcium absorption from the intestine. 242. The extracellular polysaccharides synthesized by cariogenic streptococci in the presence of excess sucrose are best described as A. B. C. D. E.

amylase. amylopectin. mucopolysaccharide. glycogen-like glucan. dextran-like glucan.

235. Which of the following functions of bone could be considered the most prominent? A. B. C. D. E.

Buffering Phosphate source Sodium reservoir Fluoride reservoir Calcium reservoir

237. The lack of which of the following substances during tooth formation most likely induces enamel hypoplasia? A. B. C. D. E.

Vitamins A and D Vitamins C and D Vitamins C and K Phosphorus and iron Calcium and fluoride

239. Which of the following is NOT a theory of the effect of parathyroid hormone on bone? A. The hormone influences the rate of bone resorption. B. The hormone causes a decrease in new bone formation. C. The action on bone is related to its action on phosphate excretion. D. The effect of parathyroid extract is to influence osteoclastic activity. 241. Which of the following sweeteners is nonnutritive as well as non-cariogenic? A. B. C. D. E.

D-fructose Saccharin Galactose Sorbitol Maltose

243. Which of the following represents a soluble polysaccharide found in dental plaque and is formed from the fructose moiety of sucrose? A. B. C. D.

Levan Dextran Amylopectin Hyaluronic acid

28

BIOCHEMISTRY NATIONAL BOARD EXAM REVIEW ANSWERS and COMMENTARY BASIC CHEMISTRY There are usually 1-2 basic chemistry questions. 1. 2. 3. 4. 5. 6. 7.

D A B B B D A

Same question in 1987 and 1998. Same question in 1985 and 1998.

BUFFERS AND pH 8.

C

9. 10. 11. 12. 13.

C B D A C

A question on the Henderson-Hasselbalch question appeared on exams in 1978, 1982, 1985, and 1998. Know this fundamental equation. Same question in 1989 and 1996. Very similar question in 1996 and 1998. Be familiar with physiologic buffers.

BICARBONATE/CO 2 There are usually 1-2 questions covering carbonic acid, bicarbonate and CO 2. 14. 15. 16. 17. 18.

D B E D A

Same question in 1978, 1981, 1985, and 1987. Very similar question in 1978, 1979, 1981 and 1996. A good question on this physiologic buffer system. A variation of this 1998 question on carbonic anhydrase appeared on the 1987 exam.

PROTEINS 19.

C

20. 21. 22. 23. 24.

B B C C E

25.

B

The same question appeared on the 1979 and 1985 exams and a variation was on 6 other exams. Know what a peptide bond is as well as the other types of bonds found in proteins (ionic, hydrogen, covalent, hydrophobic, disulfide) Same question in 1978, 1989, and 1996.

Similar questions about types of proteins, as indicated by the choice of answers, have appeared on several exams. A question on pI, pH and electrophoresis of a protein or peptide is common.

ENZYMES 26. 27. 28. 29. 30.

E B C B A

Same question in 1981, 1985, and 1987; and a similar question in 1996. Know the definition of the kinetic parameters, Km and Vmax. Know the characteristics of competitive, non-competitive, uncompetitive and

29

31.

D

32. 33. 34. 35. 36. 37. 38. 39.

A D B A D C B A

mixed inhibition. Regulation of enzyme activity by phosphorylation is a common question, often in terms of specific enzymes. Know characteristics of allosteric modifiers. There is frequently a question on enolase because it is inhibited by fluoride. Know the common zymogens and how they are activated.

COLLAGEN 40. 41. 42. 43. 44. 45.

D B C A D E

Know all aspects of collagen. Questions on post-translational modifications of collagen are very common.

HEMOGLOBIN 46. 47. 48. 49.

D C D A

50. 51.

E A

Know the effects of pH, CO2, and 2,3-bisphosphoglycerate on binding of O 2 to hemoglobin. A question related to sickle cell anemia occurs frequently.

PROTEIN SYNTHESIS 52. 53. 54. 55. 56. 57. 58.

C A C A C B E

CARBOHYDRATES 59. 60. 61. 62. 63. 64. 65. 66. 67.

C D A A B B D D D

68. 69. 70. 71.

E D D A

A question on sucrose is almost inevitable. A question on configuration is common.

Generally there are 2-3 questions on amino sugar compounds and glycoaminoglycans. (Next two questions for example.)

30

NUCLEIC ACIDS The number of questions on nucleic acids and molecular biology have increased in recent years. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85.

A E D A C D B C B A D B C C

Know base pairing.

LIPIDS Generally, lipids are emphasized: different classes of lipids, reactions, metabolism, and functions. 86. 87. 88. 89. 90. 91. 92. 93. 94.

D E A A E B B E C

95. 96. 97. 98. 99. 100. 101. 102.

C A B D D A C A

Same question on exams in 1985 and 1987. The same or similar question was on exams in 1979, 1987, and 1996. Same question on exams in 1985, 1987, and 1989. Know fatty acid synthesis and degradation ( -oxidation). See the following questions.

There is usually 1-2 questions on the composition and function of bile salts. The same or similar question appeared on at least 4 exams. Know what the different classes of serum lipoproteins transport and to where.

MEMBRANES Questions on membranes tend to focus on composition and transport. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112.

C A C E C B C B D C

31

METABOLISM Carbohydrate, amino acid, lipid, and nucleotide metabolism are included. 113. 114. 115. 116. 117. 118. 119. 120. 121. 122.

A B C E A E A A C E

123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136.

B D E D C E E C B A A A B D

137. 138. 139. 140. 141. 142. 143. 144. 145. 146. 147. 148. 149. 150. 151. 152.

A C B E B E D D C B A C B D C C

A similar question has been on at least four exams.

At least 1 question on electron transport and oxidative phosphorylation is common. See following question. A good question. The identical question or a similar one has appeared on at least 5 exams.

A good question that covers several aspects of amino acid metabolism.

At least one question on ketogenesis, ketosis, or ketone bodies is common. See following two questions.

Know cholesterol metabolism.

VITAMINS There is usually several questions on vitamins because of their involvement in many biological processes. 153. 154. 155. 156. 157. 158. 159.

E B D B D A B

A question on vitamin D is common.

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160. 161. 162. 163. 164. 165. 166. 167. 168. 169. 170.

C C B C C C E A D B D

A similar question has appeared on at least 3 exams. Know vitamin K. See following 2 questions.

NUTRITION Nutrition concerns the major food stuffs of carbohydrates, lipids and proteins, essential dietary substances, and micronutrients (vitamins and minerals). Consequently, nutrition is related to some previous subjects and the questions will overlap. 171.

C

172. 173. 174. 175. 176. 177. 178. 179. 180. 181. 182. 183. 184. 185. 186.

C E D A C B A B A A D B E A A

Esential amino acids and related metabolism tend to be emphasized. See following 4 questions.

Know calcium.

HORMONES Questions cover the chemical composition, biosynthesis, mechanism of action, and physiological functions of hormones. 187. 188. 189. 190.

E B E E

191. 192. 193. 194.

C B C D

195. 196. 197. 198. 199. 200. 201. 202.

C B D A A B A B

A good question because it covers different characteristics of a particular hormone.

Know the hyperglycemic (epinephrine, glucagon) and hypoglycemic (insulin) hormones. See the following 6 questions.

A question on aldosterone has appeared on at least 5 exams. A question on antidiuretic hormone (vasopressin) has appeared on at least 7

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203.

B

204. 205. 206. 207. 208. 209. 210. 211. 212. 213. 214. 215.

E B A A C C D A A E C A

exams. Occasionally, there is more than 1 question on vasopressin on the same exam. Questions on parathyroid hormone and calcitonin and their regulation of calcium and phosphate levels are emphasized. See the following 5 questions.

FLUORIDE 216. 217. 218. 219. 220. 221.

E A C E E B

This same question has appeared on at least 4 exams.

BLOOD CLOTTING 222. 223. 224. 225. 226. 227.

A B B A E C

BONES and TEETH The composition and properties of bones and teeth, the effects of hormones and vitamins, and caries are emphasized. 228. 229. 230. 231. 232. 233. 234. 235. 236. 237. 238. 239. 240. 241. 242. 243.

D C A C C C A E D A B B B B E A

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ADDENDUM, JUNE, 2005 In 2004, the American Dental Association released a National Board Comprehensive Part I Pilot Examination. This pilot examination was composed of 400 questions that covered Biochemistry-Physiology; Microbiology-Pathology; Dental Anatomy & Occlusion; and Anatomic Sciences. The exam was divided into two parts with 200 questions on each part (3.5 hrs for each part). Eighty percent of the questions were based on fundamental knowledge similar to those questions in the previous portion of this review material. Twenty percent of the questions were based on clinical cases (“testlets”) that each covered all four of the general subject areas noted above. There were four “testlets” on each part of the pilot exam, which each covered 5 to 13 questions. Below are Biochemistry questions from the pilot exam. I have included some “testlets” from the pilot exam, but have included only the corresponding questions that were identified as Biochemistry. The “testlets” had only a few questions that were specifically Biochemistry. Answers are given at the end of the questions. pH A1.

Which of the following describes the movement of glycine molecules in an electric field at a pH of 6.06 (the isoelectric pH for glycine)? The glycine molecules will A. B. C. D.

not move. move to the anode. move to the cathode. move to both anode and cathode.

PROTEIN, ENZYMES, HEMOGLOBIN A2.

Which of the following pairs of amino acids is expected to be found on the interior of a globular protein? A. B. C. D. E.

A4.

Pepsin Amylase Hexokinase Adenylate cyclase Carbonic anhydrase

Which of the following is an allosteric effector of an enzymatic reaction? A. B. C. D.

Competitive inhibitor Noncompetitive inhibitor Substance that binds to the substrate Substance affecting enzymatic activity by binding to the active site E. Substance affecting enzymatic activity by binding to non-active sites

Lysine and arginine Arginine and leucine Leucine and valine Valine and glutamic acid Glutamic acid and lysine

Zinc is an essential component of which of the following? A. B. C. D. E.

A3.

A5.

Which of the following describes a major effect of sickle cell anemia? A. Absence of biphosphoglycerate binding of hemoglobin B. Substitution of 2 proximal histidines C. Decreased solubility of the deoxy form of hemoglobin D. A P 50 value for hemoglobin similar to that of myoglobin E. Decreased number of subunits in hemoglobin

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COLLAGEN, EXTRACELLULAR MATRIX, ENAMEL A6. The unique amino acid composition of collagen is reflected in the high content of A. B. C. D. E. A8.

valine, threonine, and lysine. desmosine, glycine, and proline. cysteine, tyrosine, and phenylalanine. glycine, proline, and hydroxyproline. cysteine, hydroxylysine, and proline.

Which of the following vitamins is essential for the normal elaboration and maintenance of bone matrix, cartilage, and dentin? A. B. C. D.

Niacin Vitamin E Ascorbic acid Pantothenic acid

A7. Which of the following is MOST likely to promote depolymerization of extracellular matrix? A. B. C. D.

Cortisone Collagenase Chymotrypsin Hyaluronidase

A9. Which of the following statements BEST describes hydroxyapatite in enamel? A. Has a nonpolar surface B. Has 10 ions in each unit cell C. Contains no ion substitutions D. Has a higher solubility than fluorapatite E. Has a solubility that decreases as the pH decreases

CARBOHYDRATES A10. What are predominant linkages in glycogen between glucose units? A.Alpha-1,4 B.Alpha-1,6 C. Beta-1,3 D. Beta-1,4 E.Beta-1,6 A12. Which of the following is the pathway that results in the formation of glucose in the liver from lactate produced in muscle? A. B. C. D.

Cori cycle Glycolysis Citric acid cycle Pentose phosphate pathway

A11. Glucose can be made from each of the following substances EXCEPT one. Which one is this EXCEPTION? A. B. C. D. E.

Lactate Acetyl CoA Glycerol Pyruvate Fructose

A13. Which of the following mechanisms operates in liver cells to regulate breakdown of glycogen? A. Zymogen activation B. Phosphorylation of phosphorylase b to phosphorylase a C. Induction of phosphorylase b by an inducer D. Inhibition of adenylate cyclase

A14. Glucose-6-phosphatase is found associated with which of the following? A. B. C. D.

Kidneys and liver Liver and muscles Kidneys and brain Kidneys and muscles

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NUCLEIC ACIDS A15. Which of the following base pairs promotes helix stabilization in DNA but does NOT do so in RNA? A.G-C B.A-T C. G-U D. C-T E.A-U A17. DNA that is complementary to mRNA can be made using which of the following? A. B. C. D. E.

A plasmid DNA ligase A retrovirus RNA polymerase Reverse transcriptase

A19. Which of the following enzymes seals nicks in DNA? A. B. C. D. E.

Exonuclease Endonuclease Ligase DNA polymerase RNA polymerase

A21. Which of the following BEST describes restriction enzymes? A. B. C. D. E.

Exonucleases Topiosomerases Enzymes that degrade RNA Non-specific endonucleases Site-specific endonucleases

A23. Which of the following enzymes synthesizes polynucleotide chains from nucleotides and does NOT require a primer chain? A. B. C. D. E.

Ligase Exonuclease Endonuclease DNA polymerase RNA polymerase

A16. If the anticodon on transfer-RNA is 5’ACG3’, then which of the following is its corresponding codon on messenger-RNA? A. B. C. D. E.

5’ CGT 3’ 5’ CGU 3’ 5’ TGC 3’ 5’ UAG 3’ 5’ UGC 3’

A18. Which of the following represents the consequence of the fact that DNA strands are complementary? A. B. C. D.

Hairpin loop structures can be generated They will always have identical sequences Separated strands are able to reassociate They cannot get back together once separated

A20. Which of the following BEST describes the major function of histones? A. B. C. D. E.

Unwind DNA. Activate genes. Stabilize DNA in a compact form. Remove exons during RNA splicing. Stabilize RNA during transcription.

A22. Which of the following types of blotting can be used to identify DNA restriction fragments? A. B. C. D.

Eastern Southern Northern Western

A24. Which of the following is produced when a mutation occurs in an enzyme controlling a signal pathway involved in cell growth processes? A. B. C. D. E.

Epigene Antigene Oncogene Monogene Transgene

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LIPIDS A25. The first step in the pathway for fatty acid synthesis is catalyzed by an allosteric enzyme which is the principal regulator of the pathway. This enzyme is A. B. C. D. E.

thiolase. pyruvate carboxylase. citrate synthetase. acetyl CoA carboxylase. pyruvate dehydrogenase.

A27. Which of the following is a ketone body? A. B. C. D. E.

Glycerol Glucagon Acetyl CoA Acetoacetate Phosphatidycholine

A26. Each of the following is expected to be active during fatty acid biosynthesis EXCEPT one. Which one is this EXCEPTION? A. B. C. D. E.

Tricarboxylic acid cycle Pyruvate dehydrogenase Amino acid catabolism Beta oxidation Glycolysis

A28. Bile salts are sodium salts of bile acid that are conjugated with A. B. C. D.

cysteine and serine. taurine and glycine methionine and lysine. homocysteine and ornithine.

MEMBRANES/TRANSPORT A29. Facilitated diffusion DIFFERS from active transport in that net transport by facilitated diffusion

A30. The cell membrane is LEAST permeable to which of the following substances? O2 CO2 C. H2O D. Sodium E. Ethanol A.

A. B. C. D.

has a transport maximum. uses ATP as an energy source. requires a concentration gradient. occurs as an endergonic (positive ΔG) process.

A31. Active transport systems generally involve specific binding molecules that are classified as a A. B. C. D. E.

lipid. protein. lipoprotein. carbohydrate. phospholipid.

B.

A32. Which of the following provides the immediate energy source for the transport of glucose into intestinal epithelial cells? A. B. C. D.

NADH NADPH Na+ gradient across the luminal membrane H+ gradient across the luminal membrane

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METABOLISM A33. Which of the following substances is the predominant source of ATP at MODERATE levels (for greater than 60 minutes) of activity? A. B. C. D.

Amino acids Fatty acids Carbohydrates Proteins

A35. Which of the following directly catalyzes urea formation in a cell? A. B. C. D.

Urease Uricase Arginase Glutaminase

A34. The catabolism of which of the following results in no energy production in the form of ATP? A. B. C. D.

Lipid Protein Nucleotide Carbohydrate

A36. Which main product of protein nitrogen metabolism is found in human urine? A. B. C. D. E.

Urea Ammonia Creatine Uric acid Creatinine

A37. Which of the following compound is a precursor of the pigments of the skin, hair, and eyes? A. B. C. D. E.

Tyrosine Cysteine Lysine Creatine Galactosamine

HORMONES A38. Which of the following promotes the release of bile from the gallbladder? A. B. C. D. E.

Gastrin Secretin Galla Bombesin Cholecystokinin

A40. Which of the following hormones exerts the LEAST effect on calcium metabolism of bone tissues? A. B. C. D. E.

Androgen Estrogen Norepinephrine Thyroid hormone Parathyroid hormone

A39. Hormones that exert their effects through the activation of second messengers are A. lipophilic. B. usually water soluble peptide/protein hormones. C. initially bound to cytoplasmic hormone receptors. D. secreted by ovaries, testes, adrenal cortex, and placenta. A41. The biologically active conformation of trimeric G-proteins requires A. B. C. D.

the alpha-subunit to bind GDP. the alpha-subunit to bind GTP. the hydrolysis of BetaGamma-subunits. the alpha-subunit to phosphorylate downstream targets.

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VITAMINS/COENZYMES A42. Each of the following coenzymes is a component of the pyruvate dehydrogenase complex EXCEPT one. Which one is this EXCEPTION? A. B. C. D.

NAD Biotin Coenzyme A Thiamine pyrophosphate

Testlet 1. A 23-year-old female present with complaints of difficulty in opening her mouth and a lowgrade fever of several days’ duration. The medical history indicates a recent positive PPD skin test, and the patient is taking rifampin (Rifadin®). The extra-oral exam shows diffuse swelling at the angle of the right mandible and lacteral neck. Oral exam shows gingival swelling and erythema around partially erupted Tooth #32. Testlet 2. A 15-year-old male presents for emergency care. He is non-compliant with his type I diabetes regimen, and he suffered a fall while having an insulin reaction. He struck his chin and lacerated his tongue. Upon opening, his mandible deviates to the left. A panoramic radiograph reveals a fracture of the left condylar neck.

A46. The patient’s “insulin reaction” represented a sudden fall in blood glucose because he had taken his normal insulin dose but did not eat breakfast. Each of the following is a clinical manifestation of hypoglycemia EXCEPT one. Which one is this EXCEPTION? A. B. C. D. E.

Coma Dizziness Confusion Convulsion Hyperventilation

A43. Which of the following coenzymes is required for the synthesis of pyrimidines, such as thymine? A. B. C. D. E.

Niacin Thiamine Folic acid Riboflavin Pyridoxine

A44. Rifampin (Rifadin®) is effective in treating active tuberculosis because it targets which of the following pathways? A. B. C. D. E.

Mitosis Replication Translation Transcription mRNA splicing

A45. Before examining this patient, the dentist notes that the standard medical emergency kit contains an ampule of glucagon. For which of the following reasons would glucagon be used? A. Acts as a source of glucose for the hypoglycemic patient. B. Promotes glycogen formation in the hyperglycemic patient. C. Promotes glycogenolysis in the hypoglycemic patient. D. Stimulates secretion of insulin in the hyperglycemic patient. A47. Which of the following glucose transporters was responsible for the patient’s “insulin reaction”? A. B. C. D. E.

GLUT-1 GLUT-2 GLUT-3 GLUT-4 GLUT-5

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Testlet 3. An 80-year-old female with a history of cardiovascular disease presents with a complaint of pain under her complete dentures when biting. She has worn them for 15 years, but seldom removes or cleans them. Removal of the dentures reveals diffuse erythema of underlying mucosal tissue. Bone resorption is noted from detectable reduction in height of the alveolar ridges due to the ill-fitting denture.

A48. The bone resorption seen in elderly patients with low dietary calcium is enhanced by which of the following hormones? A. B. C. D. E.

Insulin Estrogen Aldosterone Thyroid stimulating hormone Parathyroid hormone

A49. Administration of a local anesthetic with epinephrine will MOST likely produce which of the following cardiovascular effects? A. B. C. D.

Increased heart rate Decreased heart rate Increased diastolic blood pressure Decreased systolic blood pressure

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Answers for Addendum, June, 2005 A1. A2. A3. A4. A5. A6. A7. A8. A9. A10. A11. A12. A13. A14. A15. A16. A17. A18. A19. A20. A21. A22. A23. A24. A25.

A C E E C D D C D A B A B A B B E C C C E B E C D

A26. A27. A28. A29. A30. A31. A32. A33. A34. A35. A36. A37. A38. A39. A40. A41. A42. A43. A44. A45. A46. A47. A48. A49.

D D B C D B C B C C A A E B C B B C D C E D E A

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