50099628 Biochemistry Samplex

MCU-FDT MEDICAL FOUNDATIONCOLLEGE 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 co-enzyme in a chemical reaction?

A. Alter the equilibrium constantB. Increase the rate of the reactionC. Maintain the pH of the reactionD. 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 equationB. 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 graphB. Eadie Hofstee plot D. Sigmoidal graph


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 dehydrogenaseB. Acid phosphatase D. Amylase


5. Which of the following properties is TRUE with reversible enzyme inhibitors?A. They bind to the active site of the enzymeB. They form enzyme substrate-inhibitor complexes [ESI complexes]C. Their effects can be reversed by increasing the concentration of the substrate

in the reactionD. The principal mode of enzyme-inhibitor interaction is covalent in nature


6. Proenzymes are catalytically important because:A. Compared to other catalytic molecules, their concentration is preferentially

regulated by transcription mechanismsB. Inactive pools of precursors are activated by covalent modification of R

groups at or near the active siteC. Their activation and inactivation are rapid, providing a readily reversible

mechanism by which enzyme activity can be regulatedD. Their activation generally involves reaction on their peptide bonds producing

active catalyst from inactive precursor poolReference: pp. 76 MPL 0.25

7. This is an example of reversible enzymes regulation by covalent modification:A. Proteolysis C. Presence of modulatorB. Enzyme induction D. Phosphorylation-dephosphorylation


8. What is Michaelis- Menten constant (Km)?A. When the substrate concentration equals the enzyme concentrationB. Is the dissociation constant of the reactionC. Is the substrate concentration that results in a half maximal reaction rateD. Is the equilibrium constant of the reaction


9. How can a non-spontaneous endergonic cellular reaction be driven to completion? By:

A. Coupling with an exergonic reactionB. Synthesis of ATPC. Addition of heatD. Increase enzyme concentration


10. The second law of thermodynamics states that in an isolated system:A. The total entropy change in a spontaneous process is always negativeB. The entropy tends to decrease with timeC. Any spontaneous process increases the entropy of the universeD. Enthalpy increases as the process proceed


11. Which of the following enzymes protects our tissues from oxygen toxicity caused by the superoxide free radical?

A. Oxidoreductases C. Superoxide dismutaseB. Oxygenases D. Hydroperoxidases


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 skinC. Prevent radiation from the sunD. Keep the integrity of the mucosa intact


13. What do you mean by uncoupling of oxidative phosphorylation?A. Separating high from low energy compoundsB. Synthesizing ATP without oxidizing substrateC. Oxidizing substrate completelyD. Oxidizing substrate without synthesis of ATP


14. This molecule accepts the electrons from cytochrome aa3 found in complex IV:A. CO C. O2

B. CO2 D. H2OReference: 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. MannoseB. Galactose D. Lactose


16. Roman, after doing his anaerobic exercise in the morning,.what is the end product in his exercising muscle?

A. Lactate C. CO2 and waterB. Pyruvate D. Acetyl CoA


17. Pyruvate dehydrogenase reaction is being biologically irreversible. What will be the effect?

A. It is inactivated by phosphorylationB. The reaction is highly endergonicC. It is not possible to make pyruvate from acetyl CoAD. The protein kinase is present in the inactive form


18. Which of the following enzymes provides a link between glycolysis and CAC?A. Acetyl CoA carbooxylase C. Pyruvate decarboxylaseB. Pyruvate carboxylase D. Pyruvate dehydrogenase


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


20. How is free glucose formed during glycogenolysis? From:A. Glucose 1-phosphate hydrolysisB. Glucose residues in 1,6 linkage to the main chainC. Glucose residues in 1,4. linkage to the main chainD. Breakdown of uridine diphosphate glucose


21. Alex is under cortisol therapy, later he develops hyperglycemia, this is due to increase:

A. Oxidation of free fatty acids in the liverB. GlycogenesisC. Peripheral utilization of glucoseD. Hepatic production of glucose by gluconeogenesis


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. LactateB. Glycerol D. Pyruvate


23. Which of the following reactions is unique to gluconeogenesis?A. Glucose 6-phosphate fructose 6-phosphateB. Oxaloacetate phosphoenolpyruvateC. Lactate pyruvateD. Phosphoenolpyruvate pyruvate


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. GlycolysisB. Pentose phosphate pathway D. Gluconeogenesis


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 transferaseB. Galactokinase D. Galactose 1-phosphate uridyl transferase


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 fecesB. Hexokinase can phosphorylate fructoseC. Liver fructose 1-phosphate aldolase is still activeD. Most tissues utilizes fructose


27. Respiratory distress syndrome seen in premature infants is due to the absence of which of the following lipids?

A. Phosphatidylglycerol C. Phosphatidyl ethanolamineB. 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. EpinephrineB. Insulin D. Protein kinase


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 CoAsB. Acetyl CoAs D. Propionyl CoAs


30. Liver cannot use ketone bodies as a source of energy primarily because they lack which of the following enzymes?

A. Acetoacetate succinyl-CoA transferaseB. β -hydroxybutyrate dehydrogenaseC. Hydroxy-methyglutaryl-CoA lyaseD. Hydroxy-methyglutaryl-CoA synthase


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 acidsB. Consists purely of unsaturated fatty acidsC. Which has a high ratio of polyunsaturated fatty acids to saturated fatty acidsD. Which has a high ratio of saturated fatty acids to polyunsaturated fatty acids


32. Which of the following statements best described essential fatty acids?A. Cannot be degraded by the bodyB. Are the only fatty acids important in the bodyC. Cannot be synthesized by the bodyD. 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 requiredB. Fatty acids are obtained from chylomicrons and VLDLC. Glycerol 3-phosphate is derived from glucoseD. A 2-monoglyceride is an intermediate


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 sphingolipidsB. Cephalin and sphingolipidsC. Neuraminic acid and lysolecithinD. Sialic acid and ceramide


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. VLDLsB. LDLs D. Chylomicrons


36. Which of the following apoprotein is found exclusively associated with chylomicrons?

A. Apo E C. Apo B-48B. Apo B-100 D. ApoA-I


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 pigmentsB. Bilirubin D. Bile acids


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. GlycineB. Alanine D. Succinyl CoA


39. Andy is resting after an overnight fast, which of the following events is true?A. Fatty acids are stored in the adipose triacylglycerolB. Liver gluconeogenesis is an important process for maintaining blood glucoseC. Liver glycogen stores are completely depletedD. Muscle glycogen stores are used to maintain blood glucose


40. Which of the following substances is being exported by the skeletal muscle in the post prandial state?

A. Alanine C. Ketone bodiesB. Glycerol D. Glucose


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 bodiesB. Glycerol D. Lactate


42. Liza has just taken her lunch, which of the following events is NOT true?A. The brain oxidizes glucose to carbon dioxide and waterB. Red blood cells oxidize glucose to carbon dioxide and waterC. Liver glycogen stores increaseD. Adipose triacylglycerol stores increase


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 bodiesB. Higher levels of blood glucoseC. More adipose tissueD. More muscle protein


44. At neutral pH, a mixture of amino acids in solution would be predominantly:A. Dipolar ions C. Negative and monovalentB. Hydrophobic molecules D. Positive and monovalent


45. In scurvy, posttranslational modification of proteins fails to result in the formation:A. Glycoproteins C. HistidineB. 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 cysteineB. 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 tetrahydrofolateB. Deficient or missing dihydrobiopterinC. Excess dietary phenylalanineD. Excess dietary tyrosine


48. Depletion of α -ketoglutarate during hyperammonemia leads to the formation of:A. Arginine C. HistidineB. Glutamine D. Proline


49. Genetic deficiency of any of the urea cycle enzymes usually results in the elevated levels of:

A. Arginine C. NH4+

B. Citrulline D. OrnithineReference: pp. 247 MPL 1.0

50. Glutamate γ -semialdehyde is a branch point metabolite in the catabolism of:A. ProlineB. Proline and ornithineC. Proline, ornithine, and arginineD. Proline, ornithine, arginuine, and hydroxyproline


51. A test dose of this amino acid provides a diagnostic test for folic acid deficiency:A. Histidine C. SerineB. Glycine D. Glutamate


52. The rate-limiting step in catecholamine biosynthesis is:A. Formation of dopamine C. Hydroxylation of phenylalanineB. Hydroxylation of tyrosine D. Reduction of dihydrobiopterin


53. The following specialized products are derived from glycine, EXCEPT:A. Creatine C. HistamineB. Heme D. Purine


54. The normal brown-red color of feces results from the presence of A. Bilirubin C. UrobilinogenB. Biliverdin D. Urobilins


55. Catabolism of heme produces bilirubin which is metabolized primarily in the:A. Blood C. KidneyB. Intestine D. Liver


56. Sunshine is fond of drinking coffee, what methylated purine is found in coffee?A. Hydroxyurea C. CaffeineB. Fluorouracil D. Thiouracils


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)


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 synthetaseC. Hypoxanthine guanine phosphoribosyltransferase D. Adenine phosphoriboxyltransferase


59. Which of the following statements is NOT true about what xanthine can be?A. A direct precursor of guanineB. A product of the enzyme xanthine oxidaseC. A substrate of the enzyme xanthine oxidaseD. Oxidized to form uric acid


60. Which of the following mutations is most likely to be lethal?A. Deletion of three nucleotidesB. Insertion of one nucleotideC. Substitution of adenine for cytosineD. Substitution of cytosine for guanine


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%


62. Ultraviolet light causes DNA damage by:A. Activation of DNA photolyase C. Formation of pyrimidine dimersB. Activation of photoreacting enzymes D. Methylation of purines


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. NondisjunctionB. Inserion D. Point mutation


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 sequencesB. Loss of the transcriptional termination sequencesC. Loss of the ribosome recognition sequencesD. Loss of the splicing consensus sequences within one introns


65. The mushroom poison amanitin is an inhibitor of the synthesis of:A. DNA C. Messenger RNAB. Glycoprotein D. Protein


66. Tetracycline prevents synthesis of polypeptides by:A. Blocking mRNA formation from DNAB. Competing with mRNA for ribosomal binding sitesC. Inhibiting tRNA binding to mRNAD. Releasing peptides from mRNA-tRNA complexes


67. Diphtheria toxin is often lethal in unimmunized persons because it:A. Blocks elongation of proteins by inactivating elongation factor 2B. Causes deletions of amino acids by speeding up the movement of

peptidyl- tRNA from the A site to the P siteC. Inhibits initiation of protein synthesis by preventing the binding of GTP

to the 40S ribosomal subunitD. Shuts off signal peptidase


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. GenomeB. Codon D. Operon


69. Which of the following is most responsible for regulating the level of eukaryotic mRNA gene products?

A. Chromatin structure C. Transcriptional initiationB. Transcript transport D. Translational initiation


70. The key structure in biologic membranes is the:A. Lipid bilayer C. RibosomesB. Membrane proteins D. Oligosaccharides


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 - gatedB. Internal ligand – gated D. Mechanically gated


72. What is the direct effect of cAMP in the protein kinase pathway in hormone actions?A. Activate adenylate cyclaseB. Dissociate regulatory subunits from protein kinaseC. Phosphorylate protein kinaseD. Release hormones from target tissues


73. Progesterone is a precursor of which of the following hormones?A. Hydrocortisone, pregnenolone and estriolB. Cholesterol, cortisone and cholic acidC. Aldosterone, cortisol, and corticosteroneD. Aldosterone, deoxycholic acid and pregnenolone


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. CortisolB. Androgen D. Estrogen


75. Which of the following hormones is derived most completely from tyrosine?A. Endorphins C. InsulinB. Glucagons D. Thyroxine


76. Hormonal stimulation of the formation of the second messenger inositol 1,4,5- triphosphate (IP3) quickly leads to the release of which other intracellular messenger?

A. Calcium C. ProstaglandinB. cAMP D. Thromboxane


77. Niacin is not strictly a vitamin since it can be synthesized in the body from this essential amino acid:

A. Proline C. ThreonineB. Valine D. Tryptophan


78. Deficiency of this vitamin causes functional folate deficiency or the so-called “folate trap”:

A. Pyredoxine C. CobalaminB. Riboflavin D. Biotin


79. This vitamin is the major lipid-soluble anti-oxidant in cell membranes and plasma lipoproteins:

A. A C. EB. D D. K


80. This is an intermediate in the synthesis of cholesterol that accumulates in the skin:A. 7 - dehydrocholesterol C. CalcidiolB. Cholecalciferol D. Calcitriol


81. Digestion of proteins differ from that of carbohydrates and fats in that:A. Proteins are initially digested in the small intestinesB. Digestion of proteins is completed in the stomachC. Most proteolytic enzymes are secreted in their zymogen formsD. The optimum pH in all phases of digestion is in the acidic range


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. GalactoseB. Fructose D. Glucose


83. Jose after eating a piece of fried chicken, the first enzyme to digest the protein of the chicken meat is:

A. Amylase C. ChymotrypsinB. Pepsin D. Trypsin


84. Muscle is comprised of this major protein:A. Actin C. TropomyosinB. Myosin D. Troponin


85. The largest protein in the body:A. Nebulin C. TitinB. Desmin D. Calcineurin

Reference: pp. 566 MPL 0.5.

86. What is the major protein responsible for 75-80% of the osmotic pressure of human plasma?

A. α -Globulin C. FibrinogenB. β -Globulin D. Albumin


87. Which immunoglobulin is actively transported across the placenta?A. IgA C. IgGB. IgD D. IgM


88. Warfarin is useful as an anticoagulant because it inhibits activation of:A. Factor X C. Platelet activationB. 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. LeukocytesB. Erythrocytes D. Platelets


90. The flexibility of the RBC membrane is due to the presence of:A. Lipids C. Integral proteinB. Peripheral proteins D. Carbohydrates


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 transportReference: pp. 611 MPL 1.0

92. The respiratory burst that occurs during phagocytosis is due to the action of:A. Catalase C. NADPH oxidaseB. Myeloperoxidase D. Superoxide dismutase


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. MyeloperoxidaseB. Integrins D. NADPH oxidase


94. The major reaction involved in Phase I xenobiotic metabolism is:A. Conjugation C. MethylationB. Hydroxylation D. Sulfation


95. This is involved in the reaction mechanism of cytochrome P450:A. NADPH C. FADB. NADH D. FADH2


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


97. Zeny, five months pregnant, her nitrogen balance is expected to be:A. At equilibrium C. NegativeB. Positive D. Variable


98. Joel for the past years always have excess caloric intake. Which of the following diseases is NOT associated with overnutirtion?

A. Cancer C. MarasmusB. Hypertension D. Type 2 diabetes mellitus


99. Vitamin D is required for the intestinal absorption of which of the following minerals?

A. Calcium C. IronB. Magnesium D. Copper


100. Alicia always maintain a balanced diet, which substances in her diet is NOT an energy source?A. Carbohydrate C. FibersB. Lipid D. Lipid


Total MPL = 51.75

Documents

50099628 Biochemistry Samplex