50099628 Biochemistry Samplex

MCU-FDT MEDICAL FOUNDATION COLLEGE OF MEDICINE DEPARTMENT OF BIOCHEMISTRY NAME: ____________________________________

DATE: __________________

MULTIPLE CHOICE: Choose the letter of the BEST answer 1. The protein enzymes are inactive without the co-enzyme. What is the function of coenzyme in a chemical reaction? A. Alter the equilibrium constant B. Increase the rate of the reaction C. Maintain the pH of the reaction D. Transfer activated group Reference: Harper’s Illustrated Biochemistry by: Murray, et al. pp. 50 MPL 0.5 2. Michaelis- Menten constant (Km) can be determined more accurately by using the: A. Lineweaver-Burk plot C. Hill equation B. Michaelis- Menten graph D. Eadie-Hofstee plot Reference: pp. 66 MPL 0.5 3. Which of the following plots / graph facilitate the evaluation of inhibitors? A. Double reciprocal plots C. Michaelis Menten graph B. Eadie Hofstee plot D. Sigmoidal graph Reference: pp. 68 MPL 0.33 4. Assay of plasma enzymes aids diagnosis and prognosis of diseases. Harry has an episode of chest pain, assay of which of the following enzymes is of help in the diagnosis? A. Alkaline phosphatase C. Lactate dehydrogenase B. Acid phosphatase D. Amylase Reference: pp. 57 MPL 1.0 5. Which of the following properties is TRUE with reversible enzyme inhibitors? A. They bind to the active site of the enzyme B. They form enzyme substrate-inhibitor complexes [ESI complexes] C. Their effects can be reversed by increasing the concentration of the substrate in the reaction D. The principal mode of enzyme-inhibitor interaction is covalent in nature Reference: pp. 71 MPL 0.33 6. Proenzymes are catalytically important because: A. Compared to other catalytic molecules, their concentration is preferentially regulated by transcription mechanisms B. Inactive pools of precursors are activated by covalent modification of R groups at or near the active site C. Their activation and inactivation are rapid, providing a readily reversible mechanism by which enzyme activity can be regulated D. Their activation generally involves reaction on their peptide bonds producing active catalyst from inactive precursor pool Reference: pp. 76 MPL 0.25 7. This is an example of reversible enzymes regulation by covalent modification: A. Proteolysis C. Presence of modulator B. Enzyme induction D. Phosphorylation-dephosphorylation Reference: pp. 78 MPL 0.33

8. What is Michaelis- Menten constant (Km)? A. When the substrate concentration equals the enzyme concentration B. Is the dissociation constant of the reaction C. Is the substrate concentration that results in a half maximal reaction rate D. Is the equilibrium constant of the reaction Reference: pp. 65 MPL 0.5 9. How can a non-spontaneous endergonic cellular reaction be driven to completion? By: A. Coupling with an exergonic reaction B. Synthesis of ATP C. Addition of heat D. Increase enzyme concentration Reference: pp. 81 MPL 0.5 10. The second law of thermodynamics states that in an isolated system: A. The total entropy change in a spontaneous process is always negative B. The entropy tends to decrease with time C. Any spontaneous process increases the entropy of the universe D. Enthalpy increases as the process proceed Reference: pp. 80 MPL 0.33 11. Which of the following enzymes protects our tissues from oxygen toxicity caused by the superoxide free radical? A. Oxidoreductases C. Superoxide dismutase B. Oxygenases D. Hydroperoxidases Reference: pp. 91 MPL 0.5 12. Juana, 65 year old has been taking vitamin E as an antioxidant to keep herself stay “young” looking. What is the action of vitamin E? A. Act as scavengers of free radicals and reduce the toxicity of oxygen. B. Act as nutrients for the skin C. Prevent radiation from the sun D. Keep the integrity of the mucosa intact Reference: pp. 91 MPL 0.5 13. What do you mean by uncoupling of oxidative phosphorylation? A. Separating high from low energy compounds B. Synthesizing ATP without oxidizing substrate C. Oxidizing substrate completely D. Oxidizing substrate without synthesis of ATP Reference: pp. 66

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14. This molecule accepts the electrons from cytochrome aa3 found in complex IV: A. CO C. O2 B. CO2 D. H2O Reference: pp. 94 MPL 0.5 15. Marie took two scoops of ice cream, a plate of pancit Malabon, and 2 slices of garlic bread. The carbohydrates content in her food has to be converted to which of the following for metabolism? A. Glucose C. Mannose B. Galactose D. Lactose Reference: pp. 110 MPL 1.0

16. Roman, after doing his anaerobic exercise in the morning,.what is the end product in his exercising muscle? A. Lactate C. CO2 and water B. Pyruvate D. Acetyl CoA Reference: pp. 143 MPL 1.0 17. Pyruvate dehydrogenase reaction is being biologically irreversible. What will be the effect? A. It is inactivated by phosphorylation B. The reaction is highly endergonic C. It is not possible to make pyruvate from acetyl CoA D. The protein kinase is present in the inactive form Reference: pp. 140 MPL 0.33 18. Which of the following enzymes provides a link between glycolysis and CAC? A. Acetyl CoA carbooxylase C. Pyruvate decarboxylase B. Pyruvate carboxylase D. Pyruvate dehydrogenase Reference: pp. 140 MPL 0.5 19. Mang David, was admitted to the hospital because of hypoglycemia, lactic acidemia, ketosis and hyperlipemia, liver biopsy done and was diagnosed to have Von Gierke’s disease. His signs and symptoms are due to the deficiency / absence of which of the following enzymes? A. Liver phosphorylase C. Glucose 6-phosphatase B. Liver phosphorylase kinase D. Debranching enzyme Reference: pp. 152 MPL 0.33 20. How is free glucose formed during glycogenolysis? From: A. Glucose 1-phosphate hydrolysis B. Glucose residues in 1,6 linkage to the main chain C. Glucose residues in 1,4. linkage to the main chain D. Breakdown of uridine diphosphate glucose Reference: pp. 148

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21. Alex is under cortisol therapy, later he develops hyperglycemia, this is due to increase: A. Oxidation of free fatty acids in the liver B. Glycogenesis C. Peripheral utilization of glucose D. Hepatic production of glucose by gluconeogenesis Reference: pp. 161 MPL 0.33 22. Carlos is diagnosed as having a genetic defect specifically in the enzyme pyruvate carboxylase. Other biotin containing enzymes are functioning normally. Which of the following substances can be used as a substrate for gluconeogenesis by Carlos? A. Alanine C. Lactate B. Glycerol D. Pyruvate Reference: pp. 159 MPL 0.33 A. B. C. D.

23. Which of the following reactions is unique to gluconeogenesis? Glucose 6-phosphate  fructose 6-phosphate Oxaloacetate  phosphoenolpyruvate Lactate  pyruvate Phosphoenolpyruvate  pyruvate Reference: pp. 153

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24. Which of the following metabolic pathways can account for the complete oxidation of glucose producing NADPH and CO2 but not ATP? A. Uronic acid pathway C. Glycolysis B. Pentose phosphate pathway D. Gluconeogenesis Reference: pp. 172 MPL 0.33 25. Helen is diagnosed to have Galactosemia, which of the following enzymes is involved in producing needed galactose in cases if diet is restricted from containing galactose or lactose? A. UDP–hexose epimerase C. Galactosyl transferase B. Galactokinase D. Galactose 1-phosphate uridyl transferase Reference: pp. 172 MPL 0.25 26. Elena is diagnosed to have familial fructokinase deficiency, but she does not present any symptoms. This is because: A. Excess fructose spills into the bowel and eliminated in the feces B. Hexokinase can phosphorylate fructose C. Liver fructose 1-phosphate aldolase is still active D. Most tissues utilizes fructose Reference: pp. 167 MPL 0.33 27. Respiratory distress syndrome seen in premature infants is due to the absence of which of the following lipids? A. Phosphatidylglycerol C. Phosphatidyl ethanolamine B. Galactosyl ceramide D. Dipalmitoylphosphatidylcholine Reference: pp. 115,202 MPL 1.0 28. An increased in which of the following hormones will increase fatty acid synthesis: A. Glucagon C. Epinephrine B. Insulin D. Protein kinase Reference: pp. 178 MPL 0.33 29. Leon, after taking a fatty meal, the fatty acids can be converted to energy by the β oxidation. What are the end products of β - oxidation? A. Acetoacetates C. Malonyl CoAs B. Acetyl CoAs D. Propionyl CoAs Reference: pp. 181 MPL 0.5 30. Liver cannot use ketone bodies as a source of energy primarily because they lack which of the following enzymes? A. Acetoacetate succinyl-CoA transferase B. β -hydroxybutyrate dehydrogenase C. Hydroxy-methyglutaryl-CoA lyase D. Hydroxy-methyglutaryl-CoA synthase Reference: pp. 186 MPL 0.25 31. Alex is diagnosed to have coronary heart disease. Which of the following diet would you recommend to him? A diet: A. Consists purely of saturated fatty acids B. Consists purely of unsaturated fatty acids C. Which has a high ratio of polyunsaturated fatty acids to saturated fatty acids D. Which has a high ratio of saturated fatty acids to polyunsaturated fatty acids Reference: pp. 190 MPL 0.5

32. Which of the following statements best described essential fatty acids? A. Cannot be degraded by the body B. Are the only fatty acids important in the body C. Cannot be synthesized by the body D. Are not important in the diet Reference: pp.190 MPL 1.0 33. Juan, after a high caloric diet consisting of fats and carbohydrates the excess calories is stored as triacylglycerols in the adipose tissue. Which of the following statements is NOT true for the synthesis of triacylglycerols in adipose tissues? A. Coenzyme A is required B. Fatty acids are obtained from chylomicrons and VLDL C. Glycerol 3-phosphate is derived from glucose D. A 2-monoglyceride is an intermediate Reference: pp. 199 MPL 0.25 34. Anita was diagnosed to have multiple sclerosis, this is a demyelinating disease due to a loss of which of the following lipids? A. Plasmalogen and sphingolipids B. Cephalin and sphingolipids C. Neuraminic acid and lysolecithin D. Sialic acid and ceramide Reference: pp. 232 MPL 0.25 35. Henry has a genetic defect resulting in a deficiency of lipoprotein lipase. After eating a fatty meal, one would expect to see elevation of which of the following in the plasma? A. HDLs C. VLDLs B. LDLs D. Chylomicrons Reference: pp. 207 MPL 1.0 36. Which of the following apoprotein is found exclusively associated with chylomicrons? A. Apo E C. Apo B-48 B. Apo B-100 D. ApoA-I Reference: pp. 206 MPL 0.5 37. Joseph took two pieces of fried eggs with bacon for his breakfast. How is the cholesterol in the eggs and bacons be excreted from his body? As: A. Bile C. Bile pigments B. Bilirubin D. Bile acids Reference: pp.229 MPL 0.5 38. Ana, a vegetarian, the cholesterol needed by her in the synthesis of all other steroids in the body can be provided by which of the following substrates? A. Acetyl CoA C. Glycine B. Alanine D. Succinyl CoA Reference: pp. 229 MPL 1.0 39. Andy is resting after an overnight fast, which of the following events is true? A. Fatty acids are stored in the adipose triacylglycerol B. Liver gluconeogenesis is an important process for maintaining blood glucose C. Liver glycogen stores are completely depleted D. Muscle glycogen stores are used to maintain blood glucose Reference: pp. 234 MPL 0.5

40. Which of the following substances is being exported by the skeletal muscle in the post prandial state? A. Alanine C. Ketone bodies B. Glycerol D. Glucose Reference: pp. 134 MPL 0.5 41. Which of the following substances is released by the adipose tissue and converted to pyruvate by the liver in the fasting state? A. Fatty acids C. Ketone bodies B. Glycerol D. Lactate Reference: pp. 234 MPL 0.5 42. Liza has just taken her lunch, which of the following events is NOT true? A. The brain oxidizes glucose to carbon dioxide and water B. Red blood cells oxidize glucose to carbon dioxide and water C. Liver glycogen stores increase D. Adipose triacylglycerol stores increase Reference: pp. 232 MPL 0.5 43. Compared to his state after an overnight fast, a person who has fasted for one week will have: A. Higher levels of blood ketone bodies B. Higher levels of blood glucose C. More adipose tissue D. More muscle protein Reference: pp. 236 MPL 0.5 44. At neutral pH, a mixture of amino acids in solution would be predominantly: A. Dipolar ions C. Negative and monovalent B. Hydrophobic molecules D. Positive and monovalent Reference: pp. 16 MPL 0.5 45. In scurvy, posttranslational modification of proteins fails to result in the formation: A. Glycoproteins C. Histidine B. Hydroxyproline D. Lipoproteins Reference: pp. 38-39 MPL 1.0 46. The non-essential amino acids synthesized from nutritionally essential amino acids are: A. Cysteine and proline C. Tyrosine and cysteine B. Proline and tyrosine D. Cysteine and serine Reference: pp.238-239 MPL 0.5 47. Severe phenylketonuria and shortened lifespan is a result of: A. Deficiency in tetrahydrofolate B. Deficient or missing dihydrobiopterin C. Excess dietary phenylalanine D. Excess dietary tyrosine Reference: pp. 255

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48. Depletion of α -ketoglutarate during hyperammonemia leads to the formation of: A. Arginine C. Histidine B. Glutamine D. Proline Reference: pp. 244 MPL 0.5

49. Genetic deficiency of any of the urea cycle enzymes usually results in the elevated levels of: A. Arginine C. NH4+ B. Citrulline D. Ornithine Reference: pp. 247 MPL 1.0 50. Glutamate γ -semialdehyde is a branch point metabolite in the catabolism of: A. Proline B. Proline and ornithine C. Proline, ornithine, and arginine D. Proline, ornithine, arginuine, and hydroxyproline Reference: pp. 249-250 MPL 0.33 51. A test dose of this amino acid provides a diagnostic test for folic acid deficiency: A. Histidine C. Serine B. Glycine D. Glutamate Reference: pp. 250 MPL 0.5 52. The rate-limiting step in catecholamine biosynthesis is: A. Formation of dopamine C. Hydroxylation of phenylalanine B. Hydroxylation of tyrosine D. Reduction of dihydrobiopterin Reference: pp. 267 MPL 1.0 53. The following specialized products are derived from glycine, EXCEPT: A. Creatine C. Histamine B. Heme D. Purine Reference: pp. 264 MPL 1.0 54. The normal brown-red color of feces results from the presence of A. Bilirubin C. Urobilinogen B. Biliverdin D. Urobilins Reference: pp. 281

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55. Catabolism of heme produces bilirubin which is metabolized primarily in the: A. Blood C. Kidney B. Intestine D. Liver Reference: pp. 278-280 MPL 1.0 56. Sunshine is fond of drinking coffee, what methylated purine is found in coffee? A. Hydroxyurea C. Caffeine B. Fluorouracil D. Thiouracils Reference: pp. 289 MPL 1.0 57. What is the first nucleotide moiety that is synthesized by de novo purine synthesis? A. Adenosine monophosphate (AMP) B. Cystidine monophosphate (CMP) C. Guanosine monophosphate (GMP) D. Insosine monophosphate (IMP) Reference: pp. 295 MPL 0.5 58. The hereditary x-linked recessive condition known as the Lesch-Nyhan syndrome is due to a severe, or complete deficiency of which of following enzymes activity? A. Ribonucleotide reductase B. PRPP synthetase C. Hypoxanthine guanine phosphoribosyltransferase D. Adenine phosphoriboxyltransferase Reference: pp. 300 MPL 0.5

59. Which of the following statements is NOT true about what xanthine can be? A. A direct precursor of guanine B. A product of the enzyme xanthine oxidase C. A substrate of the enzyme xanthine oxidase D. Oxidized to form uric acid Reference: pp. 299 MPL 0.5 60. Which of the following mutations is most likely to be lethal? A. Deletion of three nucleotides B. Insertion of one nucleotide C. Substitution of adenine for cytosine D. Substitution of cytosine for guanine Reference: pp. 362-363

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61. If the guanine content of double-helical DNA is 30% of the total bases, the thymine content would be: A. 10% C. 30% B. 20% D. 40% Reference: pp. 303 MPL 1.0 62. Ultraviolet light causes DNA damage by: A. Activation of DNA photolyase B. Activation of photoreacting enzymes Reference: pp. 335

C. Formation of pyrimidine dimers D. Methylation of purines MPL 0.33

63. Sickle cell anemia is the clinical manifestation of homozygous genes for an abnormal hemoglobin molecule. The mutational event responsible for the mutation in the β chain is: A. Deletion C. Nondisjunction B. Inserion D. Point mutation Reference: pp. 363 MPL 0.5 64. One form of β -thalassemia has been shown to result from which defect in the β globin gene? A. Loss of the transcriptional initiation sequences B. Loss of the transcriptional termination sequences C. Loss of the ribosome recognition sequences D. Loss of the splicing consensus sequences within one introns Reference: pp. 354 MPL 0.25 65. The mushroom poison amanitin is an inhibitor of the synthesis of: A. DNA C. Messenger RNA B. Glycoprotein D. Protein Reference: pp. 343

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66. Tetracycline prevents synthesis of polypeptides by: A. Blocking mRNA formation from DNA B. Competing with mRNA for ribosomal binding sites C. Inhibiting tRNA binding to mRNA D. Releasing peptides from mRNA-tRNA complexes Reference: pp. 372

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67. Diphtheria toxin is often lethal in unimmunized persons because it: A. Blocks elongation of proteins by inactivating elongation factor 2 B. Causes deletions of amino acids by speeding up the movement of peptidyl- tRNA from the A site to the P site C. Inhibits initiation of protein synthesis by preventing the binding of GTP to the 40S ribosomal subunit D. Shuts off signal peptidase Reference: pp. 372 MPL 0.33 68. A system of contiguous structural genes and controlling elements for the synthesis of various enzymes in a metabolic pathway is best described as a/an: A. Cistron C. Genome B. Codon D. Operon Reference: pp. 375-376 MPL 0.5 69. Which of the following is most responsible for regulating the level of eukaryotic mRNA gene products? A. Chromatin structure C. Transcriptional initiation B. Transcript transport D. Translational initiation Reference: pp. 391 MPL 0.33 70. The key structure in biologic membranes is the: A. Lipid bilayer C. Ribosomes B. Membrane proteins D. Oligosaccharides Reference: pp. 418

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71. This type of ion channels in the cells that opens in response to a change in membrane potential: A. External ligand – gated C. Voltage - gated B. Internal ligand – gated D. Mechanically gated Reference: pp. 424 MPL 0.5 72. What is the direct effect of cAMP in the protein kinase pathway in hormone actions? A. Activate adenylate cyclase B. Dissociate regulatory subunits from protein kinase C. Phosphorylate protein kinase D. Release hormones from target tissues Reference: pp. 460 MPL 0.33 73. Progesterone is a precursor of which of the following hormones? A. Hydrocortisone, pregnenolone and estriol B. Cholesterol, cortisone and cholic acid C. Aldosterone, cortisol, and corticosterone D. Aldosterone, deoxycholic acid and pregnenolone Reference: pp. 441

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74. Synthesis and secretion of which of the following hormones is stimulated by Angiotensin II and III, but NOT by Angiotensin I? A. Aldosterone C. Cortisol B. Androgen D. Estrogen Reference: pp. 451 MPL 0.5 75. Which of the following hormones is derived most completely from tyrosine? A. Endorphins C. Insulin B. Glucagons D. Thyroxine Reference: pp. 447 MPL 1.0

76. Hormonal stimulation of the formation of the second messenger inositol 1,4,5triphosphate (IP3) quickly leads to the release of which other intracellular messenger? A. Calcium C. Prostaglandin B. cAMP D. Thromboxane Reference: pp. 463 MPL 0.33 77. Niacin is not strictly a vitamin since it can be synthesized in the body from this essential amino acid: A. Proline C. Threonine B. Valine D. Tryptophan Reference: pp. 490 MPL 1.0 78. Deficiency of this vitamin causes functional folate deficiency or the so-called “folate trap”: A. Pyredoxine C. Cobalamin B. Riboflavin D. Biotin Reference: pp. 494 MPL 1.0 79. This vitamin is the major lipid-soluble anti-oxidant in cell membranes and plasma lipoproteins: A. A C. E B. D D. K Reference: pp. 486 MPL 1.0 80. This is an intermediate in the synthesis of cholesterol that accumulates in the skin: A. 7 - dehydrocholesterol C. Calcidiol B. Cholecalciferol D. Calcitriol Reference: pp. 484 MPL 0.5 81. Digestion of proteins differ from that of carbohydrates and fats in that: A. Proteins are initially digested in the small intestines B. Digestion of proteins is completed in the stomach C. Most proteolytic enzymes are secreted in their zymogen forms D. The optimum pH in all phases of digestion is in the acidic range Reference: pp. 477 MPL 0.5 82. Nene took a piece of cake that contains flour, milk, and sucrose as its primary ingredients, after digestion which of the following in NOT a carbohydrate products that enter the bloodstream? A. Ribose C. Galactose B. Fructose D. Glucose Reference: pp. 474 MPL 0.5 83. Jose after eating a piece of fried chicken, the first enzyme to digest the protein of the chicken meat is: A. Amylase C. Chymotrypsin B. Pepsin D. Trypsin Reference: pp. 477 MPL 1.0 84. Muscle is comprised of this major protein: A. Actin C. Tropomyosin B. Myosin D. Troponin Reference: pp.560

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85. The largest protein in the body: A. Nebulin B. Desmin Reference: pp. 566

C. Titin D. Calcineurin MPL 0.5.

86. What is the major protein responsible for 75-80% of the osmotic pressure of human plasma? A. α -Globulin C. Fibrinogen B. β -Globulin D. Albumin Reference: pp. 584 MPL 1.0 87. Which immunoglobulin is actively transported across the placenta? A. IgA C. IgG B. IgD D. IgM Reference: pp. 594

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88. Warfarin is useful as an anticoagulant because it inhibits activation of: A. Factor X C. Platelet activation B. Factor XII D. Thrombin Reference: pp. 604 MPL 1.0 . 89. Red thrombus can be distinguished from white thrombus by the presence of: A. Endothelial cells C. Leukocytes B. Erythrocytes D. Platelets Reference: pp. 598 MPL 1.0 90. The flexibility of the RBC membrane is due to the presence of: A. Lipids C. Integral protein B. Peripheral proteins D. Carbohydrates Reference: pp. 616

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91. The entry of glucose into the red blood cell is by: A. Simple diffusion C. Primary active transport B. Facilitated diffusion D. Secondary active transport Reference: pp. 611 MPL 1.0 92. The respiratory burst that occurs during phagocytosis is due to the action of: A. Catalase C. NADPH oxidase B. Myeloperoxidase D. Superoxide dismutase Reference: pp. 622 MPL 0.33 93. The enzyme present in neutrophils which is responsible for the green color of the pus and whose deficiency causes recurrent infections: A. Defensins C. Myeloperoxidase B. Integrins D. NADPH oxidase Reference: pp. 623 MPL 0.33 94. The major reaction involved in Phase I xenobiotic metabolism is: A. Conjugation C. Methylation B. Hydroxylation D. Sulfation Reference: pp. 626

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95. This is involved in the reaction mechanism of cytochrome P450: A. NADPH C. FAD B. NADH D. FADH2 Reference: pp. 627

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96. A commonly used way/method of expressing relative obesity to height is: A. Basal metabolic rate C. Specific dynamic action B. Body mass index D. Body weight Reference: pp. 478 MPL 1.0 97. Zeny, five months pregnant, her nitrogen balance is expected to be: A. At equilibrium C. Negative B. Positive D. Variable Reference: pp. 479

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98. Joel for the past years always have excess caloric intake. Which of the following diseases is NOT associated with overnutirtion? A. Cancer C. Marasmus B. Hypertension D. Type 2 diabetes mellitus Reference: pp. 480 MPL 1.0 99. Vitamin D is required for the intestinal absorption of which of the following minerals? A. Calcium C. Iron B. Magnesium D. Copper Reference: pp. 477 MPL 1.0 100. Alicia always maintain a balanced diet, which substances in her diet is NOT an energy source? A. Carbohydrate C. Fibers B. Lipid D. Lipid Reference: pp. 480 MPL 1.0

Total MPL = 51.75