Biochemistry Unknown 1

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1. The functional groups of amino acids include:

A. carboxyl and alpha carbon C. amino and carboxyl groups B. amino group and side chain D. alpha carbon and hydrogen

Reference: Murray, R.K., et. al., Harper's Illustrated Biochemistry, 26th_{ed., p. 18.}

2. Which of the following amino acids contains a polar side chain? A. Alanine C. Proline

B. Serine D. Methionine

3. Which amino acid is considered as purely ketogenic?

A. Leucine C. Isaoleucine B. Lysine D. Valine

4. The chemical bond that connects amino acids to form a polypeptide chain is: A. glycosidic bond C. van der Waals

B. peptide bond D. hydrogen bond

5. The primary sequence of proteins is determined by: A. mRNA C. tRNA

B. DNA D. hnRNA

6. Maple syrup disease is a genetic abnormality that affects the catabolism of: A. aromatic amino acids C. glycogen

B. branched -chain amino acids D. lipoproteins

Reference: Murray, R.K., et. al., Harper's Illustrated Biochemistry, 26th_{ed., p.259.}

7. The first reaction in the catabolism of amino acid is: A. deamination C. oxidation

B. decarboxylation D. dehydrogenation

8. The final product from the catabolism of amino acids is: A. uric acid C. ammonia B. urea D. nitrogen

9. The enzyme that catalyzes the reaction to release nitrogen as ammonia in the liver is: A. glutamine synthetase C. glutamine amidotransferase

B. L-glutamate dehydrogenase D. alanine transaminase

10. The enzyme that catalyzes the rate-limiting reaction in the urea synthesis is:

 A. glutamine synthetase C. carbamoyl phosphate synthetase B. alpha-ketoglutarate dehydrogenase D. ornithine decarboxylase

11. Enzymes are need in metabolic reactions because they:

A. serve as activators C. modify the configuration of the substrates B. act to stabilize reaction rates D. increase the rate of reaction

12. The catalytic activity of the enzyme is located at:

A. binding site C. cofactor

B. active site D. coenzyme

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13. What is the effect of temperature on enzyme activity?

 A. substrate binding C. denaturation of the enzyme

 B. ionization of coenzyme D. ionization of the enzyme

14. The Km or Michaelis constant is a measure of the:

 A. rate of reaction C. Vmax

B. equilibrium constant D. affinity of the substrate to the enzyme

15. A structural analogue of the substrate that can bind to the active site is called:

 A. noncompetitive inhibitor C. irreversible inhibitor B. competitive inhibitor D. uncompetitive inhibitor

16. Attachment site of amino acids to the tRNA molecule is called:

 A. anticodon C. variable loop

B. D loop D. acceptor stem

17. Termination of translation is signaled when the reading frame contains:

 A. AUG C. UAG

 B. AGA D. AGU

18. The domain of RNA polymerase that identifies the initiation site for transcription is:

 A. rho factor C. tata box

B. sigma factor D. hogness box

19. The noncoding sequence in mRNA is called:

 A. exon C. cistron

 B. muton D. intron

20. The adapter molecule during translation is:

A . tRNA C. rRNA

B. mRNA D. DNA

21. The enzyme that catalyzes replication in Hepatitis B virus:

 A. DNA polymerase C. reverse transcriptase B. RNA polymerase D. restriction enzyme

22. Which of the following contains clones that reflect mRNA sequences?

A. cDNA library C. clone

 B. DNA library D. cosmids

23. The vector used in recombinant DNA techniques that allows cloning of large DNA fragments is:

A. Plasmid C. Bacteriophage

B. Cosmid D. Intron

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24. The enzyme that catalyzes the rate-limiting step in the de novo synthesis of purine nucleotides is:

A. hypoxanthine-guanine phosphoribosyl transferase

 B. xanthine oxidase

 C. phosphoribosyl phosphate synthetase

 D. phosphoribosyl phosphate amidotransferase

25. The first purine nucleotide synthesized during the de novo pathway is:

 A. AMP C. IMP

 B. GMP D. ADP

26. Which enzyme participates in both salvage and de novo synthesis of purine and pyrimidine nucleotides?

A. Adenosine phosphoribosyl transferase B. xanthine oxidase

C. phosphoribosyl phosphate synthetase

D. phosphoribosyl phosphate amidotransferase

27. The primary product of purine catabolism is:

A. xanthine C. uric acid

B. urea D. hypoxanthine

Reference: Murray, R.K., et. al., Harper's Illustrated Biochemistry, 26th_{ed., p.299.}

28. The salvage pathway of purine nucleotide is described as: A. utilizing amphibolic intermediates.

B. is less active than the de novo synthesis C. is catalyzed by phosphoribosyl transferase D. requiring more energy than the de novo pathway

29. Which molecule is NOT a monomer of ribonucleic acids?

A. adenine C. cytidine

B. thymine D. uridine

30. The Watson - Crick model of DNA is described as:

A. A right handed double helix with the bases directed inwards A. containing 12 base pairs

B. having a pitch of 33A C. the A DNA

31. The discontinuous polymerization of DNA results in the synthesis of: A. Okazaki fragments C. exons

B. RNA D. introns

32. The following is TRUE of hemoglobin:

A. The ligand affinity to O2 is affected by allosteric factors:

B. Its tetrameric structure ensures a sigmoidal dissociation curve in all instances. C. Its quarternary interface interactions modify its O2 transport function.

D. Quarternary structural changes occur only in binding with oxygen molecules. Reference: Lehninger, A. et. al., Principles of Biochemistry, 3rd_{ed., p.s-9}

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A. Carbonic anhydrase exist in substantial amounts in the RBC as well as in the plasma.

B. To be catalytically active, carbonic anhydrase requires the alignment of multiple positive changes in the hemoglobin molecule.

C. The presence of zinc in the enzyme enhances the release of a proton (H+_{) to}

generate a OH- ion.

D. HCO3- formed binds preferentially to deoxyhemoglobin than to oxyhemoglobin.

Reference: Lehninger, A. et. al., Principles of Biochemistry, 3rd_{ed., p.s-15}

34. The following statements pertain to Bohr effect:

A. Bohr effect explains why Hgb F does NOT bind BPG (bisphosphoglycerate).

B. Bohr effect refers to the change in hemoglobin 's ligand affinity to O2 (p50) due to increase in body

temperature.

C. Bohr effect refers to the change in position of Fe++ _{and proximal histidine when the sixth}

coordination site is occupied by O2.

D. Bohr effect describes how ↓pH provides the proton to form the salt bridges of deoxyhemoglobin.

Reference: Lehninger, A. et. al., Principles of Biochemistry, 3rd_{ed., p.s-15}

35. After exposing a jaundiced infant to phototherapy, the following is true of bilirubin excretion:

A. Bilirubin is converted to bilirubin diglucoronide.

B. Phototherapy provides the sulfates needed to conjugate bilirubin. C. Bilirubin will be excreted in the feces as mesobilirubin.

D. Increased amounts of urobilin is found in the urine.

36. The fibrinolytic system of the coagulation system is characterized by: A. stabilization of the fibrin molecules by covalent cross-linkage bonding. B. glycoproteins that regulate coagulation mechanism.

C. components which are thiol-dependent transglutaminases.

D. glycoproteins that contain serine dependent active protease sites.

37. Which of the following conditions can lead to water excess? A. Diabetes mellitus C. Persistent vomiting B. Diabetes insipidus D. Congestive heart failure Reference: Berg, J. M., et. al., Biochemistry, 5th_{ed., p. 858.}

38. An exergonic reaction is one that:

A. has a positively charge standard change in free energy. B. needs an input of energy.

C. is spontaneous in nature.

D. is exemplified by anabolic reaction.

Reference: Murray, R.K., et. al., Harper's Biochemistry, 25th_{edition, p.123.}

39. The free energy change of a chemical reaction indicates which of the following? A. The spontaneity of a chemical reaction.

 B. The rate of a chemical reaction. C. The product of a chemical reaction.

 D. The reactants of the chemical reaction.

40. The first law of thermodynamics states that the:

A. energy of the universe remains constant at all times. B. energy cannot be transformed to another form.

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C. for a chemical reaction to proceed, there must be an increase in entropy. D. endergonic reaction must be coupled to exergonic reactions.

41. According to Mitchell's chemiosmotic theory, oxidative phosphorylation is dependent on: A. the concentration differences with the reduced co-enzyme and the oxidized form. C. formation of high-energy intermediate during the flow of electrons.

D. change in the conformation of proteins in the inner mitochondrial membrane.

E. protons and pH gradients created between the intermembranous space and the mitochondrial matrix.

42. Which of these fatty acids is a precursor of the prostaglandins?

A. Palmitic acid C. Oleic acid

B. Arachidonic acid D. Propionic acid

Reference: Champe, P. C., et al., Biochemistry, 2nd_{ed., p. 185}

43. Which of the following ketone bodies cannot produce energy upon oxidation? A. -hydroxybutyrate C. Acetone

B. HMG CoA D. Acetoacetate

Reference: Murray, R. K., et. al., Harper’s Biochemistry, 25th_{ed., p. 244.}

44. The immediate substrate for ketogenesis is:

A. Acetyl CoA C. Malonyl CoA

B. Fatty acyl CoA D. Citrate

Reference: Murray, R. K., et. Al., Harper’s Biochemistry, 25 th ed., p. 244. 45. The major source of NADPH for fatty acid synthesis is:

A. Pentose phosphate pathway . B. Isocitrate dehydrogenase reaction

C. Decarboxylation of malate to pyruvate in the cytoplasm D. -ketoglutarate dehydrogenase reaction

46. Hypercholesterolemic drugs inhibit this enzyme which catalyze the rate-limiting step in cholesterol synthesis:

A. HMG CoA reductase C. Cholesteryl esterase B. Squalene monooxygenase D. Mevalonate kinase

47. In the heart, the major source of energy for oxidative metabolism is:

A. Glucose C. Fatty acids

B. Lactate D. Amino acids

Reference: Murray, R. K., et. al. Illustrated Biochemistry, 26th_{ed., p. 235.}

48. Which of the following is a characteristic of the cholesterol stones?

A. They are usually formed during passage of the bile through the hepatic bile ducts. B. They occur when the mixed phospholipids-bile acid micelles are very high in phospholipids.

C. They can be dissolved by excess bile acids because the bile acids help to solubilize in micelles the water insoluble cholesterol.

D. They rarely occur because cholesterol is not a normal part of the bile.

Reference: Devlin, F. M., Textbook of Biochemistry with Clinical Correlations, 5th

ed., p.1114.

49. The key regulatory enzyme of fatty acid synthesis is: A. Fatty acid synthase C. Citrate synthase

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B. Acetyl CoA carboxylase D. Malonyl transacylase

50. Which transport system shuttles activated fatty acid molecule from the cytoplasm to the inner mitochondrial membrane during β-oxidation of fatty acids?

A. Citrate shuttle C. Malate-aspartate shuttle B. Carnitine shuttle D. Glycerol phosphate

51. The rate-limiting step of fatty acid oxidation is: A. activation of fatty acid

B. provision of fatty acid

C. transport of fatty acyl CoA into the mitochondrion D. formation of malonyl CoA

Reference: Murray, R. K. et. al., Harper’s Biochemistry, 25th_{ed., p. 239.}

52. Complete oxidation of a saturated 21-carbon fatty acid yields how many molecules of ATP?

A. 161 C. 165

B. 163 D. 167

Reference: Champe, P. C., et. al., Biochemistry, 2nd_{ed., p. 185.}

53. Carbohydrate digestion stops temporarily in the stomach because: A. carbohydrates are already digested upon reaching the stomach. B. the low gastric pH inactivates amylase.

C. there are no digestive enzymes in the stomach. D. the stomach lacks the activators for amylase.

54. Which glycolytic reaction step reoxidizes NADH2 to NAD+ and reduces pyruvate to lactate?

A. Glyceraldehyde 3-phosphate dehydrogenase reaction B. Pyruvate kinase reaction

C. Lactate dehydrogenase reaction D. Phosphofructokinase reaction

55. Which of the following compounds are involved in storing energy?

A. Glycogen C. ATP

B. Triacylglycerol D. A and B

Reference: Murray, R. K., et. al, Illustrated Biochemistry, 26th_{ed., pp. 458-460.}

56. Glucose absorption from the intestinal mucosal cell is characterized as: A. an energy-independent carrier mediated system.

B. a co-transport system with sodium.

C. transport of glucose along concentration gradient.

D. passive diffusion of glucose across the intestinal epithelial cell.

57. Glucose is a precursor of ribose and deoxyribose moieties of nucleotides and deoxynucleotides via which of the following pathways?

A. Uronic acid pathway C. Pentose phosphate pathway B. Glucose-Alanine Cycle D. Polyol pathway

58. Which of the following is TRUE of gluconeogenesis? A. It results to a net synthesis of ATP.

B. Acetyl CoA can be converted to glucose.

C. Muscles and brain can contribute to blood glucose. D. The pathway is stimulated by decreased AMP levels.

Reference: Murray, R. K. et. al., Harper’s Biochemistry, 25th_{ed.,. pp. 208-215.}

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cycle?

A. Fumarase C. Citrate synthase

B. Isocitrate dehydrogenase D. β-ketoglutarate dehydrogenase

Reference: Murray, R. K., et. al., Harper’s Biochemistry, 25th_{ed., pp184-186.}

60. Which enzyme reverses the hexokinase reaction in the liver during fasting to liberate free glucose into the blood?

A. Glucose 6-phosphatase C. Pyruvate carboxylase B. PEP carboxykinase D. Fructose 1,6-bisphosphatase

Reference: Murray, R. K. et. al., Illustrated Biochemistry, 26th_{ed., pp. 119-120.}

61. Insulin stimulates which of the following metabolic pathways? A. Glycogenolysis C. Gluconeogenesis

B. Glycolysis D. Lipolysis

Reference: Murray, R.K., et. al., Illustrated Biochemistry, 26th_{ed., p. 156.}

62. Which is NOT an intermediate of the Krebs Cycle?

A. Isocitrate C. Succinate

B. Pyruvate D. Malate

Reference: Murray, R.K., et. al., Illustrated Biochemistry, 26th_{ed., pp. 130-132.}

63. The process by which ATP is formed as a result of the transfer of electrons from NADH or FADH2 to oxygen by a series of electron carriers is called:

A. substrate level phosphorylation C. phosphorylation of an enzyme B. oxidative phosphorylation D. dephosphorylation of an enzyme

Reference: Murray, R.K., et. al., Illustrated Biochemistry, 26th_{ed., p. 94.}

64. Which of the following vitamins acts as a carrier of carbon dioxide in most carboxylation reactions?

A. Thiamine C. Biotin

B. Cobalamin D. Folic acid

Reference: Murray, R. K., et. al., Illustrated Biochemistry, 26th_{ed., p. 494.}

65. The fat soluble vitamin under current investigation for its cardioprotective properties is:

A. Vit. A C. Vit. E

B. Vit. D D. Vit. K

66. The active form of vitamin D is:

A. 7-dehydrocholesterol C. 1,25-dihydrocholecalciferol B. cholecalciferol D. 24,25-dihydroxycholecalciferol Reference: Champe, P. C., et. al, Biochemistry, 2nd_{ed., p. 335.}

67. The effects of vitamin A may include all of the following EXCEPT: A. prevention of anemia. C. the visual cycle

B. serving as an antioxidant D. induction of certain cancers

Reference: Champe, P. C. et. al., Biochemistry, 2nd_{ed., pp. 330-332.}

68. This mineral ion is a necessary co-factor in all reactions where ATP participates:

A. Cu+2 _{C. Fe}+2

B. Mn+2 _{D. Mg}+2

Reference: Berg, J. M., et. al., Biochemistry, 5th_{ed., p. 254.}

69. The second messenger of glucagon is:

A. cyclic AMP C. cyclic GMP

B. Tyrosine kinase D. Calcium

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A. Thyroxine C. Glucagon

B. Epinephrine D. Growth hormone

71. A hormone which is virilizing and can stimulate somatic growth is:

A. Estrogen C. Progesterone

B. Androgen D. Prolactin

Reference: Murray, R. K., et. al., Harper’s Biochemistry, 25thed., p. 598. 72. The following is NOT a cholesterol derived hormone:

A. Thyroxine C. Androgens

B. Calcitriol D. Estrogens

Reference: Murray, R. K, et. al., Harper’s Biochemistry, 25th_{ed., 535.}

73. Intracellular calcium is mobilized ion the cytoplasm by this PIP2-derived second messenger:

A. Protein kinase C C. Inositol diphosphate B. Inositol triphosphate D. Phosphatidylinositol

74. A transducing protein found in cell membranes which when actrivated after hormone receptor interaction activates the adenylate cyclase system:

A. Ubiquitin C. G-protein

B. Calmodulin D. Protein kinase

Reference: Murray, R. K., et. al. Illustrated Biochemistry, 26th_{ed., pp. 458-460.}

75. The most significant source of stored energy in the human body is: A. Liver glycogen C. Adipose tissue fats B. Muscle proteins D. Brain glucose

Reference: Campbell, M. K., Bichemistry, 3rd_{ed., p. 574.}

76. Positive nitrogen balance is encountered in all of the following EXCEPT:

A. Kwashiorkor C. Growth

B. Convalescence D. Pregnancy

77. The greatest fraction of the total energy requirement of an individual is provided by: A. Basal metabolism C. Diet-induced thermogenesis

B. Specific dynamic action of food D. Physical activity

78. Which of the following individuals would most likely be in nitrogen equilibrium? A. a normal, adult male C. a growing child

B. a normal, pregnant female D. an adult male recovering from surgery

ed., p. 1133.

79. Which of the following statements about dietary fibers is/are correct? A. Water soluble fiber helps to lower serum cholesterol in most people.

B. Mucilaginous fiber slows the rate of digestion and absorption of carbohydrates. C. Insoluble fiber increases stool bulk and decreases transit time.

D. All of the above are correct.

Reference: Devlin, F. M, Textbook of Biochemistry with Clinical Correlations, 5th

ed., p.1134.

80. A complete replacement of animal protein in the diet by vegetable protein: A. would be expected to have no effect at all on the overall diet.

B. would reduce the total amount of food consumed for the same number of calories. C. might reduce the total amount of iron and Vitamin B12 available.

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D. would be satisfactory regardless of the nature of the vegetable protein used.

ed., p. 1134.

81. Which of the following dietary regimens would be most effective in lowering cholesterol? A. Restrict dietary cholesterol

B. Increase the ration of polyunsaturated to saturated fatty acids. C. Restrict cholesterol and increase fiber.

D. Restrict cholesterol, increase PUFA/SFA and increase fiber.

ed., p. p.1134.

82. The main source of energy for the brain during prolonged starvation would come from:

A. Ketone bodies C. Fatty acids

B. Glucose D. Proteins

Reference: Champe, P. C., t. al., Biochemistry, 2nd_{ed., p. 294.}

83. In the overall scheme of human metabolism, which organ plays the most important role in caloric homeostasis?

A. Brain C. Liver

B. Kidney D. Muscle

Reference: Champe, P. C., et. al., Biochemistry, 2nd_{ed., p. 283, 292.}

84. In the well-fed state, the following molecules are stored XCEPT:

A. Carbohydrates C. Fats

B. Proteins D. Ketone bodies

Reference: Champe, P. C., et. al., Biochemistry, 2nd_{ed., pp. 282-289.}

85. Survival is possible in starvation because:

A. The liver synthesizes glucose from non-carbohydrate sources. B. The brain uses glucose as energy source.

C. The muscle proteins are not being continuously broken down for energy source. D. The fats are spared from degradation.

Reference: Champe, P. C., et. al., Biochemistry, 2nd_{ed., pp. 292-294.}

86. The high glucagon/insulin ratio seen in starvation:

A. promotes mobilization of fatty acids from the adipose tissues. B. stimulates β-oxidation by inhibiting the production of malonyl CoA. C. leads to increased concentration of ketone bodies in the blood. D. All of the above.

ed., p. 724. 87. In the early refed state:

A. the fatty acid concentration in the blood rises.

B. liver glycogenolysis continues to maintain blood glucose levels.

C. liver replenishes its glycogen by synthesis of glucose 6-phophate from lactate.

D. glucose being absorbed from the gut is used primarily for fatty acid synthesis by the liver. Reference: Devlin, F. M., Textbook of Biochemistry with Clinical Correlations, 5th

ed., p. 726.

88. Increased formation of ketone bodies during starvation is due to: A. increased levels of circulating glucagons.

B. decreased formation of acetyl CoA in the liver. C. increased levels of free fatty acids in the serum.

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D. inhibition of β-oxidation of fatty acids in the liver.

Reference: Champe, P. C., et. al. Biochemistry, 2nd_{ed., p.302.}

89. Which of the following is the most important source of blood glucose during the last hours of a 48-hour fast?

A. Muscle glycogen C. Liver glycogen

B. Acetoacetate D. Amino acids

90. The major cell membrane lipids are:

A. Phospholipids C. Lipoproteins

B. Cholesterol D. Fatty acids

Reference: Murray, R. K., et. al., Illustrated Biochemistry, 26th_{ed., pp. 416-417.}

91. The fluid mosaic model of biologic membranes states that:

A. there is regularity in the distribution of the proteins within a monolayer. B. the membranes are symmetrical all throughout.

C. membranes are lipid bilayers, ach with characteristic compliment of integral and peripheral proteins.

D. oligosaccharide chains are found in the cytoplasmic side of the membrane. Reference: Murray, R. K., et. al., Illustrated Biochemistry, 26th_{ed., p.}

92. The lysis of a fibrin clot:

A. is in equilibrium with the formation of a clot. B. begins when plasmin binds to the clot.

C. requires the hydrolysis of plasminogen into heavy and light chains.

D. requires the conversion of plasminogen to plasmin by tissue plasminogen activator. Reference: Devlin, F. M., Textbook of Biochemistry with Clinical Correlations, 5th

ed., p. 1051.

93. Lead poisoning would be expected to result in an elevated level of: A. Amonilevulinic acid C. Protoporphyrin I

B. Phorphobilinogen D. Hemin

Reference: Devlin, F. M., Textbook of Biochemistry with Clinical Correlations, 5th_{ed., p.1077.}

94. The cell membrane component that prevents the crystallization or coming together of two fatty acid tails is:

A. Phosphoglycerides C. Glycolipids

B. Cholesterol D. Galactolipids

95. Which is NOT an effect of erythropoietin?

A. increased RBC count C. increased oxygen delivery to the tissues B. increased hemoglobin levels D. increased aldosterone secretion

Reference: Campbell, M. K., Biochemistry, 3rd_{ed., p. 358.}

96. Parathyroid hormone is a hypercalcemic hormone because it increases:

A. intestinal absorption of calcium. C. mobilization of calcium from the bones. B. renal reabsorption of calcium. D. All of the above

Reference: Champe, P. C., Harvey, R. A., Biochemistry, 2nd_{ed., p. 310}

97. The lipoxygenase pathway of unsaturated fatty acids directs to the formation of:

A. Prostaglandins C. Thromboxanes

B. Leukotrienes D. Prostacyclins

Reference: Champe, P. C., Harve, R. A., Biochemistry, 2nd_{ed., p 187.}

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A. Synthesis of cell membranes. C. Precursor of steroid hormones. B. Synthesis of Vitamin A. D. Precursor of bile salts.

99. Megaloblastic anemia is caused by lack of:

A. Panthothenic acid C. Pyridoxine

B. Folic acid D. Ascorbic acid

Reference: Champe, P. C., Harvey, R. A., Biochemistry, 2nd_{ed., p. 326.}

100. A smoker who complains of soft swollen gums and loose teeth is deficient in Vitamin C and therefore has impaired:

A. hydroxylation of proline.

B. hydroxylation of dopamine ß-hydroxylase. C. degradation of tyrosine.

D. hydroxylation of bile acids.

Reference: Champe, P. C., Harvey, R. A., Biochemistry, 2nd_{ed., p. 40.}