Biochemistry National Board Exam Review

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 2. What thermodynamic parameter is a measure of reactions? randomness or disorder in a system?

A. Decreased entropy A. Entropy B. Increased enthalpy B. Enthalpy C. Decreased enthalpy C. Free energy D. Negative free energy change D. Potential energy E. Positive free energy change E. Activation energy

3. Atoms are isotopes of each other only if 4. Which of the following substances is LEAST polar? A. their nuclei contain the same number of neutrons. A. Ethanol B. their atomic numbers are the same, but their B. Cholesterol mass numbers differ. C. Palmitic acid C. their mass numbers are the same, but their D. Glycocholic acid atomic numbers differ. D. one is a beta emitter, but the other is an alpha emitter.

5. Which of the following characterizes an 6. Which of the following compounds does NOT asymmetric carbon? contain a high-energy bond?

A. A carbon atom with four identical groups A. ATP attached to it. B. Acetyl CoA B. A carbon atom with four different groups C. UDP-glucose attached to it. D. Glucose-6-phosphate C. A carbon with at least one carboxyl and one E. Phosphoenolypyruvate amino group attached to it. D. A carbon atom that has two heavy groups on one side and two light groups on the other.

7. Which of the following solutions has an osmotic pressure different from all the others?

A. 1 M glucose B. 1 M sodium chloride C. 1 M potassium nitrate D. 1 N lithium iodide E. 1 N hydrochloric acid 1 BUFFERS and pH

8. The Henderson-Hasselbach equations shows 9. Which of the following represents the pH of a that solution that has 10-5 M concentration of OH- ion? A. dilution of a buffer increases its pH. B. pH = pka when an acid is 0.1 N A. 5 C. pH = pka when an acid is half neutralized. B. 7 D. pH is independent of the dissociation C. 9 constant of the acid D. Determine only if the pKa is known. E. Determinable only if the base composition is known.

10. If the pH becomes lower than the isoelectric 11. A physiologic buffer functions to point of a protein, then how will the protein respond in an electrophoretic system? It will A. regulate the partial pressure of venous carbon dioxide. A. become denatured. B. carry fixed acid from the site of its B. migrate to the negative pole. elimination to the site of its production. C. migrate to the positive pole. C. transport carbon dioxide from the site of its D. remain stationary and unchanged. production to the site of its elimination. E. separate into its different monomeric forms. 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.

12. All of the following function in buffer systems in 13. The buffer system most important in maintaining the blood EXCEPT the physiological pH of plasma is

A. NaCl. A. protein/proteinate B. H2C03. B. acetic acid/acetate C. NaHCO3. C. carbonic acid/bicarbonate D. Na2HPO4. D. phosphoric acid/phosphate E. NaH2PO4. E. hydroxybutyric acid/hydroxybutyrate

BICARBONATE/CO2

14. Neutralization of acids by saliva results mainly 15. MOST of the CO2 in blood is combined as from which of the following salivary contents? A. H2C03. A. Mucin - B. HCO 3. B. Ammonia C. CH3 –COOH. C. Carbonate D. carbonic acid D. Bicarbonate E. carbaminohemoglobin. E. Amino acids

2 BICARBONATE/CO2 (Continued)

16. The bicarbonate buffer system of the blood is 17. The normal blood bicarbonate-carbonic acid very efficient because ratio is 20:1. A patient with a 10:1 ratio is in

A. bicarbonate is rapidly excreted by the A. compensated alkalosis. kidneys. B. compensated acidosis. B. bicarbonate is able to be stored in the C. uncompensated alkalosis. tissue. D. uncompensated acidosis. C. carbon dioxide is able to combine with E. none of the above. This patient’s ratio is hemoglobin within normal limits. D. carbon dioxide forms a stable combination with base. E. carbon dioxide is rapidly eliminated through the lungs.

18. Absence of which of the following blood enzymes drastically reduces blood CO2 carrying capacity?

A. Carbonic anhydrase B. Alkaline phosphatase C. Pyruvate carboxykinase D. Histidine decarboxylase E. Serum glutamic-oxaloacetate transaminase

PROTEINS

19. Removal of a molecule of water between the 20. Which of the following BEST explains why carboxyl group of one amino acid and the proteins are able to buffer physiologic solutions amino group of a second amino acid results in over a wide range of pH? formation of a A. They are macromolecules of high molecular A. zwitterion. weight. B. polypeptide. B. They contain many functional groups with C. peptide bond. differing pKs. D. hydrogen bond. C. They have unique tertiary structures that E. glycosidic bond. sequester hydrogen ions. D. They have peptide bonds that are resistant to hydrolysis.

21. Denaturation usually destroys all of the 22. Which of the following is the best method for following bonds in protein EXCEPT determining the three-dimensional structure of protein? A. hydrogen bonds. B. covalent bonds. A. Dialysis C. hydrophobic bonds. B. Electrophoresis D. electrostatic bonds. C. X-ray diffraction D. Ultracentrifugation E. None of these

3 PROTEINS (Continued)

23. The amino acid that contributes to the tertiary 24. A mucin is which of the following types of structure of a protein by causing a bend when it proteins? occurs in the primary sequence is A. Simple protein A. leucine. B. Phosphoprotein B. alanine. C. Chromoprotein. C. proline. D. Nucleoprotein. D. tyrosine. E. Glycoprotein. E. aspartic acid.

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

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

ENZYMES

26. Which of the following is true regarding 27. The optimum pH for an enzyme is the enzymes? A. isoelectric point of the enzyme. A. Are not reusable B. pH of most rapid reaction rate. B. Are needed in large amounts C. pH at which the enzyme is most soluble. C. Catalyze endergonic reactions only D. pH of most rapid denaturation of the D. Increase the energy of activation of the enzyme reaction E. Decrease the energy of activation of the reaction

28. The Km value of an enzyme is numerically equal 29. In the relationship between the concentrations to of substrate and the rate of an enzyme catalyzed reaction, the existence of a limited A. half the maximum velocity expressed in value (Vmax) of the reaction rate is due primarily moles/liter. to the B. velocity of a reaction divided by substrate concentration. A. exhaustion of the substrate supply. C. substrate concentration in moles/liter B. saturation of the enzyme with substrate. necessary to achieve half the maximum C. inhibition of the enzyme by the reaction velocity of a reaction. products. D. maximum velocity divided by half the D. denaturation of the enzyme at higher substrate concentration in moles necessary substrate concentrations. to achieve maximum velocity. E. balance between the increase in reaction rate with increasing substrate concentrations and accelerated destruction of the enzyme at higher substrate concentrations.

4 ENZYMES (Continued)

30. If the presence of a specific compound, C, 31. Protein kinase regulate the activities of key increases the Km for an enzyme-substrate enzymes through which of the following? reaction, which of the following would be true about that enzyme? A. Oxidation B. Hydrolysis A. C would be a competitive inhibitor of the C. Acetylation enzyme. D. Phosphorylation B. C would be a noncompetitive inhibitor of the E. Dephosphorylation 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 33. Enzymes for electron transport reactions are ATP also is a substrate for the enzyme. Which most active and concentrated in which of the of the following types of inhibition BEST following structures of the animal cell? explains this phenomenon? A. Nuclei A. Allosteric B. Lysosomes B. Competitive C. Microsomes C. Irreversible D. Mitochondria D. Uncompetitive E. All of the above E. Noncompetitive

34. Sodium fluoride inhibits glycolysis by affecting 35. Which of the following enzymes converts trypsinogen to trypsin? A. amylase B. enolase A. Enterokinase C. phosphatase B. Peptidase D. phosphorylase C. Secretin D. Pepsin

36. Two enzymes that have been postulated to play 37. Which of the following enzymes is essentially very important roles in calcification are absent from normal mammalian muscle?

A. enolase and phosphorylase. A. Glucokinase B. alkaline phosphatase and catalase. B. Phosphorylase C. pyrophosphatase and carbonic anhydrase. C. Glucose-6-phosphatase D. pyrophosphatase and alkaline D. Glucose-6-phosphate isomerase phosphatase. E. Glucose-6-phosphate dehydrogenase E. carbonic anhydrase and alkaline phosphatase.

5 ENZYMES (Continued)

38. Dental plaque arises primarily as a result of 39. Which of the following liver enzymes, absent enzymatic reactions using which of the from other tissues, gives the liver an advantage following? over other cells in taking up glucose after a meal? A. Sucrose and lipid B. Sucrose and saliva A. Glucokinase C. Glucose and saliva B. Aldolase D. Glucose and protein C. Hexokinase D. Enolase E. Glucose-6-phosphatase

COLLAGEN

40. The most abundant protein (by weight) in which 41. Alpha-ketoglutarate, oxygen, and ascorbic acid the human body is are essential for which of the following processes? A. elastin. B. keratin. A. Incorporation of proline C. albumin. B. Hydroxylation of proline D. collagen. C. Gamma-carboxylation of proline E. chondroitin. D. Oxidative deamination of lysine E. Activation of procollagen peptidase

42. Which of the following statements concerning 43. Hydroxylation of proline and lysine during collagen is INCORRECT? collagen biosynthesis occurs

A. Collagen has a trihelical structure. A. after translation. B. The molecular weight of collagen is above B. in the mitochondrial matrix. 100,000 C. before formation of their respective amino C. Hydroxyproline is incorporated into the acyl-tRNA’s. molecule by tRNA. D. while proline or lysine is bound to the D. Destruction of collagen can be caused by peptidyl (P) site on the ribosome. collagenases. E. Collagen contains both hydroxyproline and hydroxylysine residues.

44. The major protein produced by the odontoblast 45. Which of the following do elastin and collagen and contained in the organic matrix of dentin is have in common?

A. chitin. A. Easily stretched B. keratin. B. Absence of proline C. elastin. C. Disulfide crosslinking D. collagen. D. Triple helix structure E. cellulose. E. About one-third glycine

6 HEMOGLOBIN

46. The physiologic importance of hemoglobin lies 47. Which of the following is NOT a part of the in its ability to combine hemoglobin molecule?

A. irreversibly with oxygen and CO2. A. Iron B. reversibly with oxygen at the ferric heme B. Protein prosthetic group. C. Magnesium C. irreversibly with oxygen at the ferrous heme D. Histidine prosthetic group. E. Pyrrole ring D. reversibly with oxygen at the ferrous heme prosthetic group. E. None of the above

48. Assuming that P50 = 26 torrs, under conditions 49. The affinity of hemoglobin for oxygen where pO2 = 30 torrs, the average number of O2 diminishes as which of the following is molecules bound per hemoglobin molecule is decreased? closest to A. pH A. 0.5. B. CO2 B. less than 1. C. Temperature C. almost 2. D. Hydrogen ion concentration D. greater than 2. E. 2, 3 bisphosphoglyceric acid (BPG) E. greater than 3.

50. The consequence of appreciable conversion of 51. Compared with hemoglobin A, the substitution hemoglobin to methemoglobin is of a valine for a glutamic acid residue in hemoglobin S results from A. a significant increase in carbon dioxide combining power. A. a genetic mutation B. a significant decrease in carbon dioxide B. irradiation of hemoglobin A. combining power. C. proteolytic action in the liver. C. no effect on the ability of blood to pick up D. exposure to low oxygen tension. 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.

7 PROTEIN SYNTHESIS

52. The process by which genetic information flows 53. Which of the following enzymes or processes from RNA to protein is ensures that the correct amino acid is incorporated for a particular codon during A. mutation. protein synthesis? B. replication. C. translation. A. Amino Acyl-tRNA synthetase D. transcription. B. Ribosomal protein synthesis C. Post-transcription splicing D. RNA synthetase E. Helicase

54. Polyuridylic acid in a cell-free system capable of 55. The termination of synthesis of a polypeptide is protein synthesis results in production of believed to involve polyphenylalanine. In this system, polyuridylic acid functions as A. nonsense codons. B. anticodon-codon interaction. A. DNA. C. tRNA which cannot bind amino acids. B. transfer RNA. D. hydrolysis of messenger RNA. C. messenger RNA. E. none of the above. D. ribosomal RNA. E. mitochondrial RNA.

56. In prokaryotic protein synthesis, the elongation 57. Streptomycin is an antibiotic which inhibits the factor G serves to process of

A. form the initiation complex. A. translation in eukaryotes. B. facilitate the binding of Fmet tRNA. B. translation in prokaryotes. C. translocate the growing peptide chain and C. transcription in eukaryotes. to move the ribosome along the mRNA. D. transcription in prokaryotes. D. prevent the larger ribosomal subunits from E. DNA replication in prokaryotes. binding with those that are smaller.

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. Proline B. Arginine C. Tryptophan D. Asparagine E. Hydroxylysine

CARBOHYDRATES

59. Hydrolysis of sucrose by the enzyme sucrase 60. The arrangement of sugars into D- and L- yields configurations is based upon their resemblance to D- and L- A. glucose only. B. glucose and maltose. A. glycine. C. glucose and fructose. B. glucose. D. glucose and galactose. C. fructose. E. fructose and maltose. D. glyceraldehyde. E. None of the above

8 CARBOHYDRATES (Continued)

61. Which of the following is NOT a 62. Some carbohydrates convert Cu2+ ions to Cu+ monosaccharide? ions. This property is related to their ability to act as A. Amylose B. Glucose A. a reducing agent. C. Fructose B. an oxidizing agent. D. Glyceraldehyde C. both a reducing agent and an oxidizing E. Glucuronic acid agent. D. neither a reducing agent nor an oxidizing agent.

63. What linkages occur in glycogen at branch 64. How many anomeric carbons are present in a points between glucose units? fructose molecule?

A. Aplpha-1,4 A. 0 B. Alpha-1,6 B. 1 C. Beta-1,3 C. 2 D. Beta-1,4 D. 5 E. Beta-1,6 E. 6

65. Carbohydrate is stored in the body principally as 66. Which of the following molecule features contributes to the water-binding properties of A. glucose. proteoglycans? B. maltose. C. sucrose. A. The carboxyl groups acting as buffers D. glycogen. B. Central hyaluronate (a helix) trapping water E. glycosaminoglycans. 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 H- bonding sites.

67. Which of the following functions as part of the 68. Each of the following is a glycosaminoglycan extracellular matrix? EXCEPT one. Which one is this EXCEPTION?

A. Mucin A. Chondroitin sulfate B. Heparin B. Dermatan sulfate C. Collaginase C. Hyaluronic acid D. Chondroitin sulfate D. Heparan sulfate E. Dolichol phosphate E. Keratin

69. Glycosaminoglycans function as important 70. The carbohydrate in highest concentration in structural components of resting muscle is

A. glycogen. A. glucose. B. nucleic acids. B. lactose. C. hyaluronidase. C. sucrose. D. connective tissue. D. glycogen. E. inositol.

9 CARBOHYDRATES (Continued)

71. The most biologically important physiochemical property of connective tissue which is regulated by its mucopolysaccharide molecules is

A. viscosity. B. buffering capacity. C. solubility in dilute acides. D. supersaturation with calcium ions.

NUCLEIC ACIDS

72. Which of the following is a pyrimidine base that 73. Which of the following bonds link the monomeric is present in RNA but is NOT present in DNA? units of nucleic acids?

A. Uracil A. Ionic B. Guanine B. Peptide C. Thymine C. Thioester D. Adenine D. Glycosidic E. Cytosine E. Phosphodiester

74. In the DNA molecule, guanine on 1 strand is 75. As DNA is denatured, each of the following joined to cytosine on the complementary strand events take place EXCEPT one. Which event is by which of the following bonds? this EXCEPTION?

A. Amide A. Total G-C content of total DNA increasing B. 1 hydrogen B. UV light absorption increasing C. 2 hydrogen C. Complementary strands becoming random D. 3 hydrogen coils E. Phosphodiester D. Base stacking becoming disrupted E. Hydrogen bond breaking

76. Which of the following are NOT produced by the 77. The function of which of the following types of hydrolysis of nucleic acids? nucleic acid is to activate and select specific amino acids for protein synthesis? A. Pentoses B. Phosphates A. rRNA C. Amino acids B. mRNA D. Purine bases C. cDNA E. Pyrimidine bases D. tRNA E. hnRNA

78. If the molar percentage of A (adenine) in a 79. The degenerate nature of the genetic code native DNA specimen is 22%, then what is the implies molar content of G (guanine)? A. a common tRNA for at least two amino acids. A. 22% B. that a remarkable degree of inaccuracy B. 28% occurs in transcription. C. 44% C. the existence of multiple codons for each D. 56% amino acid. E. 78% D. the existence of multiple species of ribosomes for control of messenger translation.

NUCLEIC ACIDS (Continued) 10 80. Transcription is the cellular process of making 81. Which of the following is true of the Tm (melting temperature) of a given DNA double helix? A. new DNA. B. RNA from DNA. A. Is a function of the base composition C. proteins from amino acids by way of RNA. B. Can be used to accurately predict its D. none of the above. 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

82. DNA damage by ultraviolet light is due to 83. Each of the following is involved in gene cloning EXCEPT one. Which one is this EXCEPTION? A. alkylation of the guanine in DNA. B. excessive unwinding of the DNA molecule A. DNA ligase C. frequent replacement in the DNA molecule B. RNA polymerase of purines by pyrimidines. C. DNA polymerase I D. induction of dimerization by way of covalent D. Restriction nucleases bonds between adjacent thymine groups. E. Reverse transcriptase

84. Plasmid vectors suitable for cloning have which 85. The polymerase chain reaction is MOST useful of the following characteristics? for which of the following?

A. Must be able to replicate synchronously with A. Preparing enzymes that synthesize nucleic the host chromosome acids B. Several unique recognition sequences for B. Isolating the genome of an organism one restriction enzyme C. Amplifying a specific DNA sequence C. Two genes conferring resistance to different D. Separating polyclonal antibodies antibiotics E. Synthesizing RNA and DNA D. Large size to facilitate plasmid’s entry into cells

LIPIDS

86. Which of the following is LEAST descriptive of 87. Which of the following substances represents an lipids? unsaturated fatty acid?

A. Nonpolar A. Cholesterol B. Carbon-containing B. Palmitate C. Amphipathic C. Stearate D. Hydrophilic D. Choline E. Oleate

88. Upon complete hydrogenation, oleic, linoleic and 89. Which of the following classes of steroids linolenic acids yield contain 18 carbons and an aromatic ring?

A. stearic acid. A. Estrogens B. myristic acid. B. Androgens C. palmitoleic acid. C. Progestagens D. arachidonic acid. D. Glucocorticoids E. multiple acetate fragments. E. Mineralocorticoids

LIPIDS (Continued) 11 90. Gangliosides are glycolipids found on various 91. Neutral fats contain mixtures of one or more fatty cell surfaces. In addition to sphinogosine, their acids esterified with unit composition contains another characteristic component. This component is A. sterol. B. glycerol. A. uronic acid. C. lecithin. B. plasmalogen. D. sphinogosine. C. triglyceride. E. alcohols of high molecular weight. D. N-acetylmuramic acid. E. N-acetylneuraminic acid.

92. In addition to phosphoric acid, which of the 93. Which of the following is an essential fatty acid? following are the products of hydrolysis of lecithin? A. Acetic B. Stearic A. Glycerol, fatty acids, serine C. Myristic B. Glycerol, fatty acids, choline D. Palmitic C. Sphingosine, acetic acid, inositol E. Arachidonic D. Glyceraldehyde, fatty acids, choline E. Glyceraldehyde, fatty acids, ethanolamine

94. Carbon dioxide or bicarbonate is required in the 95. The enzyme catalyzing the rate-controlling step biosynthesis of fatty acids because in the de novo synthesis of fatty acids is regulated allosterically by the positive modulator A. the bicarbonate/carbonic acid buffer system is very efficient at the pH optimum of this A. ATP. sensitive enzyme system. B. NADPH. B. bicarbonate is a positive effector for this C. Citrate. system and favorably alters the conformation D. cyclic AMP. of its enzymes. E. oxaloacetate. 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 97. Beta oxidation of a mole of an 18 carbon fatty even-numbered fatty acids differs from that of acid under physiologic conditions produces the catabolism of fatty acids in that A. one mole of acetic acid. A. malonyl CoA is an intermediate in synthesis. B. nine moles of acetyl CoA. B. acyl carrier protein is needed in catabolism. C. nine moles of acetic acid. C. no flavoprotein enzymes are required for D. one mole of acetoacetic acid. catabolism. E. one mole of hydroxybutyric acid. D. propionyl CoA may serve as an intermediate in synthesis.

LIPIDS (Continued)

12 98. Sodium taurocholate and glycocholate are 99. After functioning in the small intestines, the necessary for the absorption of largest portion of bile salts are

A. sucrose. A. excreted in the feces. B. glycerol. B. reabsorbed into the central lacteal. C. amino acids. C. destroyed by bacteria in the large D. fatty acids. intestines. E. nucleic acids. D. reabsorbed into the portal circulation and reused. E. removed from the circulation by the kidneys and excreted in the urine.

100. Which of the following is MOST often 101. Triglyceride absorbed into the lymphatic associated with free fatty acid transport in system is transported to the liver as which of human blood? the following?

A. Albumin A. Very low density lipoprotein B. Globulin B. Low density lipoprotein C. Cholesterol C. Chylomicrons D. Sphingolipid D. Liposomes E. Mucopolysaccharide E. Micelles

102. Which of the following compounds is an intermediate in the biosynthesis of cholesterol?

A. Squalene B. Hexosamine C. Cholic acid D. Pregnanediol E. Deoxycholic acid

MEMBRANES

103. The major lipids that make up the cell 104. The most abundant nonphospholipid membrane are component of the cell membrane is

A. triglycerides. A. cholesterol. B. sphingomyelins. B. deoxycholate. C. phospholipids. C. prostaglandin. D. fatty acids. D. macroglobulin. E. steroids. E. triacylglyceride.

105. Each of the following lipid classes is 106. Which of the following represents a incorporated into membranes EXCEPT one. polyunsaturated fatty acid that is commonly Which one is this EXCEPTION? found in animal cell membranes?

A. Cholesterol A. Oleic B. Ganglioside B. Lactic C. Triglyceride C. Sialic D. Sphingomyelin D. Stearic E. Phosphatidylcholine E. Linoleic

MEMBRANES (Continued) 13 107. The fluid-mosaic model for membrane structure 108. The major driving force for formation of a lipid proposes that micelle is

A. the outer and inner faces of the membrane A. protein-lipid interaction. are identical. B. hydrophobic interaction between B. peripheral proteins are situated only on the hydrocarbon tails. outer face of the plasma membrane. C. hydrogen bonding between water C. integral proteins are associated with the molecules of the micellar core. hydrophobic phase of the bilayer. D. electrostatic interaction between the D. both polar and nonpolar ends of membrane micellar core and polar heads. phospholipids are within the hydrophobic phase of the bilayer.

109. Which of the following molecules would likely 110. The rapid movement of a substance across a form a micelle when mixed with water and biologic membrane against a concentration agitated? gradient requires

A. Serine A. that the substance be negatively charged. B. Glycerol B. participation of an energy-requiring active C. Phospholipid transport system. D. Triglyceride 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

111. Mediated (facilitated) diffusion of substances 112. Which of the following features distinguishes across cell membranes differs from simple active transport from facilitated diffusion? diffusion in that mediated diffusion A. Specificity A. requires ATP. B. Carrier-mediated B. requires another solute. C. Requires metabolic energy C. is a one-directional process. D. Presence of a transport maximum (Tm) D. exhibits saturation kinetics.

METABOLISM

113. Reactions that have unfavorable energetics 114. A common intermediate of metabolism of (i.e., + ∆G0) in metabolic pathways may be carbohydrates, fatty acids and amino acids is driven to completion by which of the following processes? A. glycerol. B. acetyl CoA. A. Coupling C. acetoacetate. B. Allosterism D. oxaloacetate. C. Modification E. acetylcholine. D. Microscopic reversibility

METABOLISM (Continued) 14 115. A number of catabolic pathways are 116. In the glycolytic sequence, the enzyme that allosterically inhibited by an increase in the brings about the transition from 6-carbon concentration of which of the following? metabolites to 3-carbon metabolites is

A. ADP A. phosphoglucoisomerase. B. AMP B. phosphofructokinase. C. ATP C. phosphorylase. D. NAD+ D. hexokinase. E. Pyruvate E. aldolase.

117. Under strict anaerobic conditions, the 118. Muscle glycogen does not yield blood glucose catabolism of one glucose molecule would directly but liver glycogen does because yield a net of A. hexokinase is not present in liver. A. 2 ATP and 2 lactic acid molecules. B. muscle cells are impermeable to glucose. B. 4 ATP and 2 lactic acid molecules. C. muscle does not contain C. 2 ATP and 2 pyruvic acid molecules. phosphoglucomutase. D. 4 ATP and 2 pyruvic acid molecules. D. muscle glycogen differs in structure from liver glycogen. E. glucose-6-phosphatase is not present in muscle.

119. Enzymes that catalyze the anaerobic 120. Cyclic 3’, 5’-AMP increases the rate of processes of carbohydrate metabolism are glycogenolysis by found predominantly in which part of a cell? A. promoting the formation of a A. Cytoplasm phosphorylated form of glycogen B. Membrane phosphorylase. C. Cell wall B. serving as a substrate for glycogen D. Nucleus phosphorylase. E. Mitochondria C. serving as a precursor of 5’ AMP which is a cofactor for glycogen phosphorylase. D. furnishing phosphate for the phosphorolysis of glycogen.

121. Consider the conversion: alanine – lactic acid 122. Energy for ATP synthesis is derived from the – glucose. This is an example of electron transport system by which of the following processes? A. glycolysis. B. glycogenolysis. A. Transamination C. gluconeogenesis. B. Aldolization D. synthesis of glycerol. C. Reductive synthesis D. Oxidative deamination E. Oxidative phosphorylation

METABOLISM (Continued)

15 123. The chemical energy generated by 124. Functions of the hexose monophosphate shunt mitochondrial electron transport results from include the production of which of the following? (1) NADP for lactate oxidation. A. Excess H+ in the matrix (2) NADPH for fatty acid synthesis. B. An H+ gradient across the inner (3) glucuronic acid for heparin synthesis. membrane (4) D-ribose for nucleic acid synthesis. C. The formation of thioesters in the matrix (5) ATP for anaerobic muscle contraction. D. A conformational change in the inner membrane A. (1), (3), and (5) B. (1) and (4) C. (2), (3), and (5) D. (2) and (4) E. (3) only

125. Which of the following represents the chemical 126. The tricarboxylic acid cycle is initiated by the substance that is the immediate source of condensation of which of the following two energy for muscle contraction? molecules?

A. Glycogen A. Pyruvate and malate B. Acetyl CoA B. NAD+ and oxaloacetate C. Lactic acid C. NAD+ and oxalosuccinate D. Creatine phosphate D. Acetyl coenzyme A and oxaloacetate E. Adenosine triphosphate E. Acetyl coenzyme A and oxalosuccinate

127. Enzymes concerned with the citric acid cycle 128. Acids found in the citric acid (Krebs) cycle are are found in the A. glutamic acid and succinic acid. A. nucleus. B. glucuronic acid and aspartic acid. B. ribosomes. C. oxaloacetic acid and aspartic acid. C. mitochondria. D. oxaloacetic acid and pyruvic acid. D. nonparticulate cytoplasm. E. oxaloacetic acid and α-ketoglutaric acid. E. None of the above

129. If protein is catabolized for energy, then MOST 130. Which of the following is the FIRST step in the of the energy is derived from which of the catabolism of many amino acids? following? A. Formation of a dipeptide with glutamate A. Urea production B. Conjugation of the alpha amino to B. Oxidative deamination glucuronate C. Transamination reactions C. Transamination of the alpha amino to a D. Cleavage of peptide bonds keto acid E. Oxidation of α-keto acids derived from D. Conjugation of the alpha carboxyl group to amino acids. glucuronate E. Decarboxylation of the alpha carboxyl group to form a primary amine

16 131. Which of the following statements is NOT true 132. The level of nonprotein nitrogen in the blood is about ammonia and the α-amino group of due principally to the level of which of the amino acids? following?

+ A. NH 4 is formed from glutamine in the A. Urea kidney. B. Ammonia B. The amino group in carbamyl phosphate is C. Creatine directly donated by aspartate in a D. Arginine transamination reaction. E. Uric acid 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 134. Which of the following tissues is primarily reaction? responsible for formation of urea?

α-ketoglutarate + alanine = pyruvate + P A. Liver B. Brain A. Glutamate C. Kidney B. Glutamine D. Muscle C. Aspartate D. Succinate E. Pyridoxine phosphate

135. After prolonged acidosis, which of the following 136. Excessive utilization of fats by the body as a represents the nitrogenous product that is source of energy during disturbances in excreted in high amounts in the urine? carbohydrate metabolism can lead to all of the following conditions EXCEPT A. Urea B. Ammonia A. ketosis. C. Uric acid B. acidosis. D. Creatinine C. ketonuria. E. Aspartic acid D. alkalosis.

137. In relative insulin insufficiency, acetyl CoA is 138. The ketone body acetoacetate is synthesized usually channeled into inside mitochondria of hepatocytes by

A. ketone-body formation. A. carboxylation of pyruvic acid. B. cholesterol synthesis. B. transamination of aspartic acid. C. fatty-acid synthesis. C. cleavage of β-hydroxy- β-methylglutaryl D. gluconeogenesis. CoA. E. the Krebs cycle D. oxidative decarboxylation of α- ketoglutarate. E. oxidation of L-β-hydroxybutyrate followed by deacylation.

17 139. The final step in the complete metabolism of 140. Mobilization of fat stored in adipocytes fat is carried out by means of involves

A. anaerobic glycolysis. A. activation of fatty acids by synthesis of acyl B. the tricarboxylic acid cycle. CoA. C. the reductive fixation of CO2. B. rearrangement of fatty acids in D. the hexose monophosphate shunt. triglycerides. E. the Krebs-Henseleit (urea) cycle. 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.

141. How do inadequate insulin levels, such as 142. Prostaglandins are made within cells those which occur in diabetes mellitus, affect fat metabolism? A. on an RNA template. B. on rough endoplasmic reticulum. A. Glucose utilization is increased. C. from methionine. B. Utilization of fat for energy is increased. D. from progesterone. C. Storage of cholesterol by the Kupffer cells E. from polyunsaturated fatty acids. is increased. D. Level of beta-hydroxybutyric acid in the urine is depressed.

143. The metabolite, 25-hydroxycholecalciferol is 144. Which of the following is necessary for de derived MOST immediately from novo synthesis of cholesterol?

A. ergosterol. A. NAD+ B. cholesterol. B. NADH C. 7-dehydro-sitosterol. C. NADP+ D. 7-dehydro-cholesterol. D. NADPH E. 22-dihydro-ergosterol. E. FADH2

145. Most endogenous cholesterol in the liver is 146. Ribose phosphate needed for nucleic acid usually converted into which of the following? synthesis can be derived from

A. Glucose A. gluconeogenesis. B. Steroids B. the pentose phosphate pathway. C. Cholic acid C. the Krebs’ tricarboxylic acid cycle. D. Oxaloacetate D. decarboxylation of aromatic amino acids. E. Ketone bodies E. one-carbon transfer from tetrahydrofolate derivatives.

147. Purine ribonucleoside phosphates are all 148. Which of the following enzymes catalyzes the synthesized de novo from the common formation of uric acid from purines? intermediate A. Urease A. inosine phosphate. B. Uricase B. guanosine phosphate. C. Xanthine oxidase C. adenosine phosphate. D. Aspartate transcarbamoylase D. guanosine diphosphate. E. Carbamoyl-phosphate synthetase E. deoxyadenosine phosphate.

18 149. Which of the following is a source of 150. Coenzyme A participates in transferable methyl groups in metabolism? A. formylation. A. Valine B. protein synthesis. B. Choline C. methionine activation. C. Leucine D. activation of carboxyl groups. D. Isoleucine

151. Tay-Sach disease is associated with an inborn 152. Glucosuria with hyperglycemia usually occurs error of metabolism involving a specific in which of the following? enzyme which normally degrades a particular molecule in the gray matter. This enzyme acts A. Pellagra on which of the following? B. Addison’s disease C. Diabetes mellitus A. Polysaccharides D. Diabetes insipidus B. Acylglycerols E. Parkinson’s disease C. Gangliosides D. Fatty acids E. Proteins

VITAMINS

153. Which of the following is a vitamin? 154. The general reaction for the transfer of a “one- carbon fragment” requires the coenzyme A. Adenine B. Inosine A. pyridoxal phosphate. C. Xanthine B. tetrahydrofolic acid. D. Thyroxin C. thiamine pyrophosphate. E. Pyridoxine D. flavin adenine dinucleotide. E. diphosphopyridine nucleotide.

155. Pantothenic acid is an integral part of 156. Derivatives of riboflavin and niacin function as

+ A. NAD . A. CO2 acceptors B. cobalamin. B. coenzymes in redox reactions. C. folic acid. C. factors in transamination reactions. D. coenzyme A. D. replacements for each other in biologic E. pyridoxine phosphate. reactions.

157. A vitamin derivative concerned with conversion 158. Which of the following vitamins is necessary of glucose to lactic acid is as a coenzyme in the initial steps of fatty acid synthesis? A. thiamine (as cocarboxylase). B. pantothenic acid (as coenzyme A). A. Biotin C. pyridoxal (as pyridoxal phosphate). B. Thiamine D. nicotinamide (as nicotinamide adenine C. Vitamin A dinucleotide). D. Vitamin D E. Riboflavin

VITAMINS (Continued)

19 159. Which of the following is required for vitamin 160. Hydroxylation at the 1 position of 25- D3 synthesis? hydroxycholecalciferol occurs primarily in the

A. Decarboxylation in the liver A. skin. B. UV activation of precursors in skin B. liver. C. Metabolism by gut bacteria C. kidney. D. Deamination in the kidney D. intestinal mucosa.

161. Vitamin A functions to 162. A deficiency of vitamin A in a developing tooth most likely affects the A. prevent pellagra. B. promote absorption of calcium. A. pulp. C. promote differentiation of epithelial cells. B. enamel. D. maintain the integrity of connective C. dentin. tissues. D. cementum.

163. The effect of a vitamin C deficiency on the 164. Which of the following is a function of vitamin developing tooth is primarily on the B6 (pyrodoxal phosphate)? calcification of dentin and cementum. This can best be explained by which of the following A. Prevents pernicious anemia statements? B. Allows adaptation to dim light C. Acts as coenzyme in transamination A. This does happen, but the reason is reaction obscure. D. Prevents microcytic hypochromic anemia 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 166. A derivative of vitamin K is the coenzyme for cofactor in formation of acetyl CoA from which of the following? pyruvate? A. Production of menadiol A. NAD+ B. Esterfication of retinol B. FAD C. Hydrolysis of peptide bonds C. Pyridoxine D. Cross-linking of fibrinogen D. Lipoic acid E. Carboxylation of glutamate side chains E. Thiamine pyrophosphate

VITAMINS (Continued)

20 167. The function of vitamin K is involved directly 168. Which of the following vitamins can be with supplied to humans by the normal action of intestinal flora? A. synthesis of prothrombin. B. activation of the Stuart factor. A. A C. regulation of calcium in the blood. B. D D. conversion of fibrinogen to fibrin. C. E E. transcriptional control for fibrinogen D. K synthesis. E. None of the above

169. Osteoblasts form the organic matrix of bone 170. To which of the following avitaminoses is the prior to calcification of the tissue. This process gingival most susceptible? requires vitamins A. A A. A and B12. B. B2 B. A and C. C. B6 C. A and D. D. C D. C and E. E. Niacin E. D and E.

NUTRITION

171. Some amino acids need not be present in the 172. Negative nitrogen balance (nitrogen excretion diet of an animal because of the animal’s > intake) may be cause by ability to synthesize the acids at an adequate rate. A principal source of carbon for these A. growth. amino acids is B. protein synthesis. C. dietary lack of essential amino acid. A. nucleic acids. D. synthesis and catabolism of equal B. carbon dioxide. amounts of body protein. C. metabolism of carbohydrates. D. methylene folic acid derivatives.

173. Which of the following groups includes only 174. Which of the following amino acids lessens the amino acids essential for humans? need for phenylalanine?

A. Valine, serine, leucine A. Lysine B. Leucine, lysine, glycine B. Leucine C. Tyrosine, threonine, tryptophan C. Glycine D. Phenylalanine, methionine, proline D. Tyrosine E. Tryptophan, methionine, isoleucine E. Tryptophan

175. A diet rich in tryptophan offsets a deficiency of 176. A deficiency of rhodopsin is most likely caused which of the following vitamins? by decreased dietary intake of

A. Niacin A. glucose. B. Thiamine B. adenine. C. Riboflavin C. vitamin A. D. None of the above D. tryptophan. E. riboflavin.

NUTRITION (Continued) 21 177. Lipid is required in the average diet because it 178. A deficiency of choline in the diet can cause abnormalities in the metabolism of A. has a high caloric value. B. provides essential fatty acids. A. lipids. C. aids in absorption of carbohydrates. B. proteins. D. is necessary for storage of carbohydrates. C. minerals. D. carbohydrates. E. nucleoproteins.

179. Purine bases taken in the human diet in the 180. Which of the following minerals are most form of DNA or RNA are mostly frequently in short supply in American diet?

A. excreted as urea. A. Calcium and iron B. excreted in the form of uric acid. B. Calcium and iodine C. reused and converted to ATP needed as a C. Sulfur and potassium source of energy. D. Iodine, magnesium and iron D. broken down to give NH3 and either malonic acid or methylmalonic acid.

181. Which of the following represents the amount 182. A diet deficient in calcium will result in of dietary calcium normally absorbed from the gut of an adult man? A. stimulation of the thyroid gland. B. increased ability to cross-link fibrin. A. An amount less than 50% C. production of calcitonin and a low blood B. An amount between 60-70% calcium level. C. An amount between 80-100% D. production of parathyroid hormone and D. An amount dependent up the mucosal bone resorption. ferritin level

183. The recommended daily dietary allowances for 184. Which of the following must be digested before Ca and P provide a Ca/P intake of being in a form that can be absorbed by approximately enterocytes?

A. 0.5. A. Monoglycerides B. 1.0 B. Fatty acids C. 2.0. C. Fructose D. 3.0. D. Glycine E. 4.0. E. Maltose

185. Which of the following is secreted more during 186. A sustained, severe carbohydrate deficiency in the absorptive state than during the the diet will result in which of the following? postabsorptive state? A. Ketoacidosis A. Insulin B. Severe metabolic alkalosis B. Glucagon C. A deficiency in prostaglandin formation C. Cortisol D. An inability to synthesize ascorbic acid D. Thyroxine E. Ephinephrine

HORMONES

22 187. Which of the following hormones is a 188. Iodine is primarily important in the biochemical polypeptide? synthesis of

A. Epinephrine A. ACTH. B. Testosterone B. thyroxin. C. Progesterone C. adrenalin. D. Triiodotyronine D. calcitonin. E. Follicle-stimulating hormone E. parathyroid hormone.

189. Which of the following hormones is NOT 190. In which of the following combinations is the synthesized from cholesterol? name of the hormone, its chemical type and its tissue of origin correctly matched? A. Progesterone B. Testosterone A. Aldosterone-peptide-pancreas C. Estradiol B. Glucagon-peptide-adrenal cortex D. Cortisol C. Epinephrine-steroid-adrenal medulla E. Relaxin D. ACTH-polypeptide-adrenal cortex E. Vasopressin-peptide-posterior pituitary

191. Each of the following characterizes a peptide 192. Which of the following generates a slowly hormone EXCEPT one. Which one is this developing long-term response in target EXCEPTION? tissues by binding to an intracellular receptor?

A. Stored in secretory granules A. Glucagon B. Synthesized in a precursor form B. Estrogen C. Binds to intracellular receptors C. Prolactin D. Acts by generating a second messenger D. Growth hormone E. Usually transported unbound in plasma E. Parathyroid hormone

193. The intracellular, “second” messenger for 194. Epinephrine causes an elevation in cAMP many peptide and polypeptide hormones is levels in muscle cells which in turn activate

A. AMP. A. ATPase. B. ATP. B. adenyl cyclase. C. cyclic AMP. C. glycogen synthetase. D. adenylate cyclase. D. glycogen phosphorylase. E. a cytoplasmic receptor. E. glycogen phosphorylase phosphatase.

195. The hyperglycemic effect of glucagon is 196. Two hormones which act similarly to increase mediated primarily through glycogen and lipid breakdown as well as cyclic AMP synthesis are A. the growth hormone. B. muscle glycolysis. A. insulin and calcitonin. C. liver glycogenolysis. B. glucagon and epinephrine. D. inhibition of cortisol action. C. aldosterone and testosterone. E. enhanced glucose reabsorption by renal D. parathyroid hormone and glucagon. tubules.

197. Which of the following takes place as 198. Which of the following hormones does NOT proinsulin is converted to insulin? induce activation of adenylate cyclase?

A. Disulfide bonds are formed. A. Insulin B. Disulfide bonds are broken. B. Glucagon C. The polypeptide chain is lengthened. C. Epinephrine D. A segment of the polypeptide chain is D. Parathyroid hormone removed.

23 HORMONES (Continued)

199. Inhibition of lipolysis, stimulation of protein 200. Which of the following is a principal action of synthesis and increased entry of glucose into insulin? muscles and adipose tissues are biologic actions of the hormone A. To mobilize lipid deposits B. To enhance cell permeability to glucose A. insulin. C. To decrease cell permeability to glucose B. cortisol. D. To conserve glucose by breaking down C. glucagons. amino acids D. epinephrine. E. testosterone.

201. Aldosterone is normally associated with partial 202. Which of the following BEST explains the regulation of which of the following processes? primary action of antidiuretic hormone?

A. Sodium balance A. It decreases the activity of the Na-K pump B. Gluconeogenesis in the distal tubule. C. Lipid digestion B. It increases the H2O permeability of the D. Protein degradation collecting ducts and the distal tubules. E. Carbohydrate metabolism 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.

203. The parathyroid hormone acts in the body by 204. Each of the following is an effect of parathyroid hormone EXCEPT one. Which one is this A. decreasing absorption of calcium in the EXCEPTION? intestinal tract. B. accelerating the removal of calcium and A. Stimulation of 1-alpha-hydroxylase in phosphate from the skeleton but not from kidney the teeth. B. Stimulation of osteoclastic activity in bone C. stimulating gluconeogenesis in the liver. C. Stimulation of calcium reabsorption by D. decreasing the excretion of sodium and kidney chloride. D. Inhibition of phosphate reabsorption by E. All of the above kidney E. Inhibition of intestinal absorption of calcium

205. Hyperparathyroidism is marked by 206. The low serum phosphate level in hyperparathyroidism is caused by A. chronic tetany. B. a high blood calcium level. A. increased renal loss of phosphate. C. retention of phosphates by the kidneys. B. decreased absorption of phosphate. D. storage of excess minerals in the bones. C. increased deposition of calcium phosphate E. increased irritability of excitable tissues. in bone. D. increased reabsorption of calcium phosphate from bone.

HORMONES (Continued)

24 207. A parathyroidectomized animal will exhibit 208. Which of the following are the immediate which levels of calcium and phosphate ion effects of calcitonin on serum levels of calcium concentration in the plasma? and phosphate?

Calcium Phosphate ion Serum calcium Serum phosphate concentration A. Increased Increased A. Low High B. Increased Decreased B. Normal Low C. Decreased Decreased C. High Low D. No change Increased D. Normal Normal E. Decreased No change E. Low Low

209. Hydrolysis of thyroglobulin liberates a number 210. Thyroid hormones, glucocorticoids and of iodinated compounds. Two are considered gonadal steroids are similar in that each thyroid hormones. These are A. is derived from cholesterol. A. tyrosine and thyronine. B. is derived from amino acids. B. tyrosine and diiodotyrosine. C. acts on only one target organ or tissue. C. thyroxin and triiodothyronine. D. is released in response to signals from D. thyroxin and triiodotyrosine. the hypothalamic-anterior pituitary complex. E. is released in response to signals from the hypothalamic-posterior pituitary complex.

211. Which of the following describes the principal 212. The physiologically active form of vitamin D mechanism by which glucocorticoids stimulate produced in the kidney is their target cells? A. 1,25-dihydroxycholecalciferol. A. They activate specific genes. B. 25-hydroxycholecalciferol. B. They activate initiation factors for protein C. 7-dehydrocholesterol. synthesis. D. cholecalciferol. C. They increase the intracellular Ca++ E. ergosterol. 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 214. Secretin functions in digestion of proteins by hormone increasing

A. gastrin. A. flow of bile. B. secretin. B. secretion of pepsin. C. pancreozymin. C. flow of pancreatic juice. D. enterogastrone. D. secretion of carboxypeptidase. E. cholecystokinin.

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 217. Fluoroapatite can form during hard tissue reducing dental decay is most likely the result formation by a (an) of A. substitution of OH ions by F ions. A. an increase in hardness of the tooth. B. reaction between CaF2 and CaHPO4. B. an inhibition of proteolytic enzymes. C. reaction of F ions with hydroxylysine C. deposition of CaF2 in areas of enamel residues. susceptible to bacterial penetration. D. absorption of F ions onto hydroxyapatite D. an increase in carbohydrate metabolism in crystal surfaces. 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 219. The anticaries effect of fluoride is LEAST concerning fluoride? related to which of the following?

A. It is expected rapidly by the kidney. A. Ion exchange B. It is deposited in calcified tissues. B. Decreased solubility C. It occurs only in the ionic form in plasma. C. Facilitation of remineralization D. It passes the placental barrier relatively D. Its presence during enamel formation slowly. E. Activation of plaque polysaccharide E. At 1 ppm. In water, it is tasteless, odorless hydrolysis and colorless.

220. The rate of fluoride incorporation into bone 221. Sodium fluoride inhibits glycolysis by affecting depends upon the which of the following?

A. water-mineral ratio. A. Amylase B. age of the individual. B. Enolase C. rate of bone remodeling or turnover. C. Phosphatase D. amount of ionizable fluoride in the diet. D. Phosphorylase E. All of the above

BLOOD CLOTTING

222. A deficiency in vitamin K would affect blood 223. Platelets play an important role in hemostasis. clotting chiefly by Which of the following describes this role?

A. decreasing prothrombin production. A. They convert fibrinogen to fibrin. B. preventing the contraction of the clot. B. They agglutinate and plug small, ruptured C. preventing the reaction of thrombin with vessels. fibrinogen. C. They initiate fibrinolysis in thrombosis. D. preventing the conversion of fibrinogen to D. They supply fibrin stabilizing factor. fibrin. E. They supply proconvertin for E. preventing the conversion of prothrombin thromboplastin activation. to thrombin.

BLOOD CLOTTING (Continued) 26 224. Administration of heparin to a human results in 225. Which of the following compounds is NOT symptoms similar to vitamin K deficiency in involved in coagulation of blood? that both conditions result in A. Fe+2 A. release of lipoprotein lipase to the blood B. Ca+2 and rapid clearance of chylomicrons. C. Prothrombin B. and increase in bleeding time due to lack D. Fibrinogen of thrombin formation. E. Thromboplastin 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 227. Which of the following ions is involved in blood substrate of thrombin? clotting?

A. Fibrin A. Iron B. Thrombospondin B. Sodium C. Prothrombin C. Calcium D. Thromboplastin D. Potassium E. Fibrinogen

BONES AND TEETH

228. The organic matrix of bone is composed 229. Which of the following represent(s) the matrix largely of collagen and proteins of enamel?

A. lipids. A. Carboxylglutamic acid containing proteins B. citrate. B. Type I collagen C. dextrans. C. Amelogenins D. glycosaminoglycans. D. Proteoglycans E. Elastin

230. Which of the following explains why enamel is 231. Which of following is the major protein harder than bone? component of cementum?

A. Enamel crystals are larger and more firmly A. Elastin packed. B. Keratin B. Enamel contains amelogenins in its C. Collagen organic matrix. D. Amelogenin C. Enamel contains more magnesium and E. Osteonectin carbonate. D. Enamel crystals have more surface area. E. Enamel contains more collagen.

232. Which of the following noncollagenous protein 233. Which of the following has a high affinity for components BEST characterizes dentin binding calcium and collagen in the calcifying matrix? matrix?

A. Laminin A. Calcitonin B. Vimentin B. Osteogenin C. Phosphophoryn C. Osteonectin D. Osteonectin D. Amelogenin E. Fibronectin E. Fibronectin BONES AND TEETH (Continued) 27 234. Protein content of enamel from mature teeth is 235. Which of the following functions of bone could approximately what per cent of enamel be considered the most prominent? weight? A. Buffering A. 0.1-1% B. Phosphate source B. 5-10% C. Sodium reservoir C. 15-20% D. Fluoride reservoir D. 25-30% E. Calcium reservoir E. 50-55%

236. Which of the following BEST characterizes 237. The lack of which of the following substances hydroxyapatite? during tooth formation most likely induces enamel hypoplasia? A. Has an amphiphilic surface B. Contains 12 ions per unit cell A. Vitamins A and D C. As found in bone and enamel contains no B. Vitamins C and D ion substitutions C. Vitamins C and K D. Has a higher solubility product constant D. Phosphorus and iron than fluoroapatite E. Calcium and fluoride

238. Which of the following vitamins is the LEAST 239. Which of the following is NOT a theory of the likely to be involved in tooth development and effect of parathyroid hormone on bone? calcification? A. The hormone influences the rate of bone A. A resorption. B. B1 B. The hormone causes a decrease in new C. C bone formation. D. D C. The action on bone is related to its action on phosphate excretion. D. The effect of parathyroid extract is to influence osteoclastic activity.

240. The primary effect of calcitonin is to 241. Which of the following sweeteners is non- nutritive as well as non-cariogenic? A. increase bone resorption. B. inhibit bone resorption. A. D-fructose C. increase calcium absorption from the B. Saccharin intestine. C. Galactose D. decrease calcium absorption from the D. Sorbitol intestine. E. Maltose

242. The extracellular polysaccharides synthesized 243. Which of the following represents a soluble by cariogenic streptococci in the presence of polysaccharide found in dental plaque and is excess sucrose are best described as formed from the fructose moiety of sucrose?

A. amylase. A. Levan B. amylopectin. B. Dextran C. mucopolysaccharide. C. Amylopectin D. glycogen-like glucan. D. Hyaluronic acid E. dextran-like glucan.

28 BIOCHEMISTRY NATIONAL BOARD EXAM REVIEW

ANSWERS and COMMENTARY

BASIC CHEMISTRY There are usually 1-2 basic chemistry questions.

1. D 2. A Same question in 1987 and 1998. 3. B Same question in 1985 and 1998. 4. B 5. B 6. D 7. A

BUFFERS AND pH

8. C A question on the Henderson-Hasselbalch question appeared on exams in 1978, 1982, 1985, and 1998. Know this fundamental equation. 9. C Same question in 1989 and 1996. 10. B Very similar question in 1996 and 1998. 11. D Be familiar with physiologic buffers. 12. A 13. C

BICARBONATE/CO2 There are usually 1-2 questions covering carbonic acid, bicarbonate and CO2.

14. D Same question in 1978, 1981, 1985, and 1987. 15. B Very similar question in 1978, 1979, 1981 and 1996. 16. E A good question on this physiologic buffer system. 17. D 18. A A variation of this 1998 question on carbonic anhydrase appeared on the 1987 exam.

PROTEINS

19. C 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) 20. B Same question in 1978, 1989, and 1996. 21. B 22. C 23. C 24. E Similar questions about types of proteins, as indicated by the choice of answers, have appeared on several exams. 25. B A question on pI, pH and electrophoresis of a protein or peptide is common.

ENZYMES

26. E 27. B 28. C Same question in 1981, 1985, and 1987; and a similar question in 1996. 29. B Know the definition of the kinetic parameters, Km and Vmax. 30. A Know the characteristics of competitive, non-competitive, uncompetitive and mixed inhibition. 29 31. D Regulation of enzyme activity by phosphorylation is a common question, often in terms of specific enzymes. 32. A Know characteristics of allosteric modifiers. 33. D 34. B There is frequently a question on enolase because it is inhibited by fluoride. 35. A Know the common zymogens and how they are activated. 36. D 37. C 38. B 39. A

COLLAGEN

40. D Know all aspects of collagen. 41. B 42. C 43. A Questions on post-translational modifications of collagen are very common. 44. D 45. E

HEMOGLOBIN

46. D 47. C 48. D 49. A Know the effects of pH, CO2, and 2,3-bisphosphoglycerate on binding of O2 to hemoglobin. 50. E 51. A A question related to sickle cell anemia occurs frequently.

PROTEIN SYNTHESIS

52. C 53. A 54. C 55. A 56. C 57. B 58. E

CARBOHYDRATES

59. C A question on sucrose is almost inevitable. 60. D A question on configuration is common. 61. A 62. A 63. B 64. B 65. D 66. D 67. D Generally there are 2-3 questions on amino sugar compounds and glycoaminoglycans. (Next two questions for example.) 68. E 69. D 70. D 71. A

30 NUCLEIC ACIDS The number of questions on nucleic acids and molecular biology have increased in recent years.

72. A 73. E 74. D 75. A 76. C 77. D 78. B Know base pairing. 79. C 80. B 81. A 82. D 83. B 84. C 85. C

LIPIDS Generally, lipids are emphasized: different classes of lipids, reactions, metabolism, and functions.

86. D 87. E 88. A 89. A 90. E 91. B Same question on exams in 1985 and 1987. 92. B The same or similar question was on exams in 1979, 1987, and 1996. 93. E 94. C Same question on exams in 1985, 1987, and 1989. Know fatty acid synthesis and degradation ( -oxidation). See the following questions. 95. C 96. A 97. B 98. D There is usually 1-2 questions on the composition and function of bile salts. 99. D The same or similar question appeared on at least 4 exams. 100. A 101. C Know what the different classes of serum lipoproteins transport and to where. 102. A

MEMBRANES Questions on membranes tend to focus on composition and transport.

103. C 104. A 105. C 106. E 107. C 108. B 109. C 110. B 111. D 112. C

31 METABOLISM Carbohydrate, amino acid, lipid, and nucleotide metabolism are included.

113. A 114. B 115. C 116. E 117. A 118. E A similar question has been on at least four exams. 119. A 120. A 121. C 122. E At least 1 question on electron transport and oxidative phosphorylation is common. See following question. 123. B 124. D A good question. 125. E The identical question or a similar one has appeared on at least 5 exams. 126. D 127. C 128. E 129. E 130. C 131. B A good question that covers several aspects of amino acid metabolism. 132. A 133. A 134. A 135. B 136. D At least one question on ketogenesis, ketosis, or ketone bodies is common. See following two questions. 137. A 138. C 139. B 140. E 141. B 142. E 143. D Know cholesterol metabolism. 144. D 145. C 146. B 147. A 148. C 149. B 150. D 151. C 152. C

VITAMINS There is usually several questions on vitamins because of their involvement in many biological processes.

153. E 154. B 155. D 156. B 157. D 158. A 159. B A question on vitamin D is common. 160. C 161. C 32 162. B 163. C 164. C A similar question has appeared on at least 3 exams. 165. C 166. E Know vitamin K. See following 2 questions. 167. A 168. D 169. B 170. D

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 Esential amino acids and related metabolism tend to be emphasized. See following 4 questions. 172. C 173. E 174. D 175. A 176. C 177. B 178. A 179. B 180. A 181. A Know calcium. 182. D 183. B 184. E 185. A 186. A

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

187. E 188. B 189. E 190. E A good question because it covers different characteristics of a particular hormone. 191. C 192. B 193. C 194. D Know the hyperglycemic (epinephrine, glucagon) and hypoglycemic (insulin) hormones. See the following 6 questions. 195. C 196. B 197. D 198. A 199. A 200. B 201. A A question on aldosterone has appeared on at least 5 exams. 202. B A question on antidiuretic hormone (vasopressin) has appeared on at least 7 exams. Occasionally, there is more than 1 question on vasopressin on the same exam. 33 203. B Questions on parathyroid hormone and calcitonin and their regulation of calcium and phosphate levels are emphasized. See the following 5 questions. 204. E 205. B 206. A 207. A 208. C 209. C 210. D 211. A 212. A 213. E 214. C 215. A

FLUORIDE

216. E This same question has appeared on at least 4 exams. 217. A 218. C 219. E 220. E 221. B

BLOOD CLOTTING

222. A 223. B 224. B 225. A 226. E 227. C

BONES and TEETH The composition and properties of bones and teeth, the effects of hormones and vitamins, and caries are emphasized.

228. D 229. C 230. A 231. C 232. C 233. C 234. A 235. E 236. D 237. A 238. B 239. B 240. B 241. B 242. E 243. A

34 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. not move. B. move to the anode. C. move to the cathode. D. move to both anode and cathode.

PROTEIN, ENZYMES, HEMOGLOBIN

A2. Which of the following pairs of amino acids is A3. Which of the following is an allosteric effector expected to be found on the interior of a of an enzymatic reaction? globular protein? A. Competitive inhibitor A. Lysine and arginine B. Noncompetitive inhibitor B. Arginine and leucine C. Substance that binds to the substrate C. Leucine and valine D. Substance affecting enzymatic activity by D. Valine and glutamic acid binding to the active site E. Glutamic acid and lysine E. Substance affecting enzymatic activity by binding to non-active sites

A4. Zinc is an essential component of which of the A5. Which of the following describes a major effect following? of sickle cell anemia?

A. Pepsin A. Absence of biphosphoglycerate binding of B. Amylase hemoglobin C. Hexokinase B. Substitution of 2 proximal histidines D. Adenylate cyclase C. Decreased solubility of the deoxy form of E. Carbonic anhydrase hemoglobin D. A P 50 value for hemoglobin similar to that of myoglobin E. Decreased number of subunits in hemoglobin

35 COLLAGEN, EXTRACELLULAR MATRIX, ENAMEL

A6. The unique amino acid composition of collagen A7. Which of the following is MOST likely to is reflected in the high content of promote depolymerization of extracellular matrix? A. valine, threonine, and lysine. B. desmosine, glycine, and proline. A. Cortisone C. cysteine, tyrosine, and phenylalanine. B. Collagenase D. glycine, proline, and hydroxyproline. C. Chymotrypsin E. cysteine, hydroxylysine, and proline. D. Hyaluronidase

A8. Which of the following vitamins is essential for A9. Which of the following statements BEST the normal elaboration and maintenance of describes hydroxyapatite in enamel? bone matrix, cartilage, and dentin? A. Has a nonpolar surface A. Niacin B. Has 10 ions in each unit cell B. Vitamin E C. Contains no ion substitutions C. Ascorbic acid D. Has a higher solubility than fluorapatite D. Pantothenic acid E. Has a solubility that decreases as the pH decreases

CARBOHYDRATES

A10. What are predominant linkages in glycogen A11. Glucose can be made from each of the between glucose units? following substances EXCEPT one. Which one is this EXCEPTION? A.Alpha-1,4 B.Alpha-1,6 A. Lactate C. Beta-1,3 B. Acetyl CoA D. Beta-1,4 C. Glycerol E.Beta-1,6 D. Pyruvate E. Fructose

A12. Which of the following is the pathway that A13. Which of the following mechanisms operates in results in the formation of glucose in the liver liver cells to regulate breakdown of glycogen? from lactate produced in muscle? A. Zymogen activation A. Cori cycle B. Phosphorylation of phosphorylase b to B. Glycolysis phosphorylase a C. Citric acid cycle C. Induction of phosphorylase b by an D. Pentose phosphate pathway inducer D. Inhibition of adenylate cyclase

A14. Glucose-6-phosphatase is found associated with which of the following?

A. Kidneys and liver B. Liver and muscles C. Kidneys and brain D. Kidneys and muscles

36 NUCLEIC ACIDS

A15. Which of the following base pairs promotes A16. If the anticodon on transfer-RNA is 5’ACG3’, helix stabilization in DNA but does NOT do so then which of the following is its corresponding in RNA? codon on messenger-RNA?

A.G-C A. 5’ CGT 3’ B.A-T B. 5’ CGU 3’ C. G-U C. 5’ TGC 3’ D. C-T D. 5’ UAG 3’ E.A-U E. 5’ UGC 3’

A17. DNA that is complementary to mRNA can be A18. Which of the following represents the made using which of the following? consequence of the fact that DNA strands are complementary? A. A plasmid B. DNA ligase A. Hairpin loop structures can be generated C. A retrovirus B. They will always have identical sequences D. RNA polymerase C. Separated strands are able to reassociate E. Reverse transcriptase D. They cannot get back together once separated

A19. Which of the following enzymes seals nicks in A20. Which of the following BEST describes the DNA? major function of histones?

A. Exonuclease A. Unwind DNA. B. Endonuclease B. Activate genes. C. Ligase C. Stabilize DNA in a compact form. D. DNA polymerase D. Remove exons during RNA splicing. E. RNA polymerase E. Stabilize RNA during transcription.

A21. Which of the following BEST describes A22. Which of the following types of blotting can be restriction enzymes? used to identify DNA restriction fragments?

A. Exonucleases A. Eastern B. Topiosomerases B. Southern C. Enzymes that degrade RNA C. Northern D. Non-specific endonucleases D. Western E. Site-specific endonucleases

A23. Which of the following enzymes synthesizes A24. Which of the following is produced when a polynucleotide chains from nucleotides and mutation occurs in an enzyme controlling a does NOT require a primer chain? signal pathway involved in cell growth processes? A. Ligase B. Exonuclease A. Epigene C. Endonuclease B. Antigene D. DNA polymerase C. Oncogene E. RNA polymerase D. Monogene E. Transgene

37 LIPIDS

A25. The first step in the pathway for fatty acid A26. Each of the following is expected to be active synthesis is catalyzed by an allosteric enzyme during fatty acid biosynthesis EXCEPT one. which is the principal regulator of the pathway. Which one is this EXCEPTION? This enzyme is A. Tricarboxylic acid cycle A. thiolase. B. Pyruvate dehydrogenase B. pyruvate carboxylase. C. Amino acid catabolism C. citrate synthetase. D. Beta oxidation D. acetyl CoA carboxylase. E. Glycolysis E. pyruvate dehydrogenase.

A27. Which of the following is a ketone body? A28. Bile salts are sodium salts of bile acid that are conjugated with A. Glycerol B. Glucagon A. cysteine and serine. C. Acetyl CoA B. taurine and glycine D. Acetoacetate C. methionine and lysine. E. Phosphatidycholine D. homocysteine and ornithine.

MEMBRANES/TRANSPORT

A29. Facilitated diffusion DIFFERS from active A30. The cell membrane is LEAST permeable to transport in that net transport by facilitated which of the following substances? diffusion A. O2 A. has a transport maximum. B. CO2 B. uses ATP as an energy source. C. H2O C. requires a concentration gradient. D. Sodium D. occurs as an endergonic (positive ΔG) E. Ethanol process.

A31. Active transport systems generally involve A32. Which of the following provides the immediate specific binding molecules that are classified energy source for the transport of glucose into as a intestinal epithelial cells?

A. lipid. A. NADH B. protein. B. NADPH C. lipoprotein. C. Na+ gradient across the luminal D. carbohydrate. membrane E. phospholipid. D. H+ gradient across the luminal membrane

38 METABOLISM

A33. Which of the following substances is the A34. The catabolism of which of the following results predominant source of ATP at MODERATE in no energy production in the form of ATP? levels (for greater than 60 minutes) of activity? A. Lipid A. Amino acids B. Protein B. Fatty acids C. Nucleotide C. Carbohydrates D. Carbohydrate D. Proteins

A35. Which of the following directly catalyzes urea A36. Which main product of protein nitrogen formation in a cell? metabolism is found in human urine?

A. Urease A. Urea B. Uricase B. Ammonia C. Arginase C. Creatine D. Glutaminase D. Uric acid E. Creatinine

A37. Which of the following compound is a precursor of the pigments of the skin, hair, and eyes?

A. Tyrosine B. Cysteine C. Lysine D. Creatine E. Galactosamine

HORMONES

A38. Which of the following promotes the release of A39. Hormones that exert their effects through the bile from the gallbladder? activation of second messengers are

A. Gastrin A. lipophilic. B. Secretin B. usually water soluble peptide/protein C. Galla hormones. D. Bombesin C. initially bound to cytoplasmic hormone E. Cholecystokinin receptors. D. secreted by ovaries, testes, adrenal cortex, and placenta.

A40. Which of the following hormones exerts the A41. The biologically active conformation of trimeric LEAST effect on calcium metabolism of bone G-proteins requires tissues? A. the alpha-subunit to bind GDP. A. Androgen B. the alpha-subunit to bind GTP. B. Estrogen C. the hydrolysis of BetaGamma-subunits. C. Norepinephrine D. the alpha-subunit to phosphorylate D. Thyroid hormone downstream targets. E. Parathyroid hormone

39 VITAMINS/COENZYMES

A42. Each of the following coenzymes is a A43. Which of the following coenzymes is required component of the pyruvate dehydrogenase for the synthesis of pyrimidines, such as complex EXCEPT one. Which one is this thymine? EXCEPTION? A. Niacin A. NAD B. Thiamine B. Biotin C. Folic acid C. Coenzyme A D. Riboflavin D. Thiamine pyrophosphate E. Pyridoxine

Testlet 1. A44. Rifampin (Rifadin®) is effective in treating active tuberculosis because it targets which of A 23-year-old female present with complaints the following pathways? of difficulty in opening her mouth and a low- grade fever of several days’ duration. The A. Mitosis medical history indicates a recent positive PPD B. Replication skin test, and the patient is taking rifampin C. Translation (Rifadin®). The extra-oral exam shows diffuse D. Transcription swelling at the angle of the right mandible and E. mRNA splicing lacteral neck. Oral exam shows gingival swelling and erythema around partially erupted Tooth #32.

Testlet 2. A45. Before examining this patient, the dentist notes that the standard medical emergency kit A 15-year-old male presents for emergency contains an ampule of glucagon. For which of care. He is non-compliant with his type I the following reasons would glucagon be diabetes regimen, and he suffered a fall while used? having an insulin reaction. He struck his chin and lacerated his tongue. Upon opening, his A. Acts as a source of glucose for the mandible deviates to the left. A panoramic hypoglycemic patient. radiograph reveals a fracture of the left B. Promotes glycogen formation in the condylar neck. hyperglycemic patient. C. Promotes glycogenolysis in the hypoglycemic patient. D. Stimulates secretion of insulin in the hyperglycemic patient.

A46. The patient’s “insulin reaction” represented a A47. Which of the following glucose transporters sudden fall in blood glucose because he had was responsible for the patient’s “insulin taken his normal insulin dose but did not eat reaction”? breakfast. Each of the following is a clinical manifestation of hypoglycemia EXCEPT one. A. GLUT-1 Which one is this EXCEPTION? B. GLUT-2 C. GLUT-3 A. Coma D. GLUT-4 B. Dizziness E. GLUT-5 C. Confusion D. Convulsion E. Hyperventilation

40 Testlet 3. A48. The bone resorption seen in elderly patients with low dietary calcium is enhanced by which of the An 80-year-old female with a history of following hormones? cardiovascular disease presents with a complaint of pain under her complete dentures when biting. She A. Insulin has worn them for 15 years, but seldom removes or B. Estrogen cleans them. Removal of the dentures reveals C. Aldosterone diffuse erythema of underlying mucosal tissue. Bone D. Thyroid stimulating hormone resorption is noted from detectable reduction in E. Parathyroid hormone height of the alveolar ridges due to the ill-fitting denture.

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

A. Increased heart rate B. Decreased heart rate C. Increased diastolic blood pressure D. Decreased systolic blood pressure

41 Answers for Addendum, June, 2005

A1. A A26. D A2. C A27. D A3. E A28. B A4. E A29. C A5. C A30. D A6. D A31. B A7. D A32. C A8. C A33. B A9. D A34. C A10. A A35. C A11. B A36. A A12. A A37. A A13. B A38. E A14. A A39. B A15. B A40. C A16. B A41. B A17. E A42. B A18. C A43. C A19. C A44. D A20. C A45. C A21. E A46. E A22. B A47. D A23. E A48. E A24. C A49. A A25. D