Biochem Final Examination 2007

Biochemistry Final Examination 2007 1.

The nucleus is a prominent spherical or oval structure, located usually near the center of the cell. It is the “control centre” of all cell activities. Which of the following does “NOT” form a part of the nucleus of a eukaryotic animal cell? a. Nucleolus b. chromatin material c. nucleoplasm d. mitochondria

2.

The plasma membrane is the outer covering of every cell, which separates its contents from everything around it. It provides a mechanical barrier for the protection of the inner cell contents. It is said to be “selectively permeable.” What does this mean? a. The plasma membrane regulates the movement of molecules in and out of the cell. b. There are pores in the plasma membrane, which allows the exchange of genetic material between two adjacent cells, leading to variation. c. The plasma membrane ensures that the cell forms part of tissue only which it is meant for. d. The plasma membrane can dissipate at the time of mitosis.

3.

Name the disaccharide and the glycosidic link found in the structure shown:

a.

Β(1,3) b. fructose, α(1-4)

c. lactose, Β(1-4)

d. maltose, α(1-6)

4.

On the linear projection of an aldose structure, the D configuration depends on the orientation of the hydroxyl group of what carbon? a. 6th carbon b. 5th carbon c. 1st carbon d. 2nd carbon

5.

Which level of protein structure refers to the amino acid sequence in a protein and stabilized mainly by peptide bonds? a. Primary b. secondary c. tertiary d. quaternary

6.

Which a. b. c. d.

7.

Which amino acid is classified as essential and has an R group that is polar and charged at physiologic pH? a. Phenylalanine b. glutamic acid c. lysine d. valine

8.

Which of the following statements regarding fatty acids is NOT CORRECT? a. They are considered as aliphatic carboxylic acids, occurring mainly as exters in natural fats and oils. b. Most are usually long-chain containing an even number of carbon atoms

c. d.

9.

Which a. b. c. d.

10. Which a. b. c.

d.

of the following is true of the zwitterion form of an amino acid? Has equal number of amino and carboxylic groups Moves towards both the cathode and anode during electrophoresis Predominant amino acid species at the isoelectric pH Will bear a net negative charge at low pH

Most naturally occurring unsaturated fatty acids has cis double bonds. Their melting points decrease with chain length and increase according to unsaturation. of the following is TRUE regarding complex lipids? Cholesterol is considered a minor phospholipids Phosphatidylcholine is considred to be the most abundant phospholipids of the cell membrane Glycolipids contain a fatty acid, glycerol, carbohydrate and no sphingosine Sphingomyelins contain ceramide, phosphoric acid and lecithin statement is true regarding the chemical nature of biological membranes? The integral proteins in the inner layer rotate by flip-flop movement to the outer layer. Membrane fluidity is primarily maintained by the hydrophilic domains in the component lipids. The component lipids are asymmetrically assembled in the outer and inner leaflets of the membrane. The hydrophobic character of the phospholipids increases the membrane permeability to ions such as Na+ and Cl-.

11. As a principal component of biological membranes, peripheral proteins: 1

a. b. c. d.

Span the entire lipid bilayer Loop back and forth within the aqueous core of the membrane Are composed of hydrophobic amino acids which interact with the oily core of the bilyer Are situated on the surface of the membrane and constitute its cytoskeleton

12. When the energy of activation of an enzyme catalyzed reaction is lowered, which of the following is expected? a. Enzyme is denatured c. reaction will do into equilibrium b. Velocity of the reaction increases d. reaction rate decreases 13. Different forms of enzymes that catalyze same reactions which could help in diagnosis of specific tissue pathology when these enzymes are elevated: a. Coenzymes b. apoenzymes c. isoenzymes d. holoenzymes 14. Kinetic parameters that characterize enzymes: a. Kcat and Vi c. Km and Vmax b. Q10 and [E] d. [S] and turnover number

15. Which of the following is an important cofactor for redox (dehydrogenation) reaction? a. Tetrahydrofolic acid b. thiamine pyrophosphate c. NAD d. biotin 16. All of the following coenzyme and vitamin component are paired correctly EXCEPT: a. FAD and vitamin B2 c. Coenzyme A and Pantothenic acid b. Pyridoxal phosphate and vitamin B6 d. Lipoic acid and Vitamin C 17. All of the following are components of the total energy expenditure EXCEPT this one: a. Resting energy expenditure c. physical activity b. Basal energy expenditure d. thermal effect of food 18. Normally the distribution of the total energy expenditure for 24hrs. to carbohydrates, proteins and fats is: a. 60%, 25%, 15% respectively c. 50%, 30%, 20% respectively b. 60%, 15%, 25% respectively d. 50%, 20%, 30% respectively 19. Appetite is stimulated by: a. Leptin b. insulin

c. Agouti related peptide

d. PYY3-36

20. The amount of energy that is used to perform useful work is termed: a. Enthalpy b. entropy c. free energy d. endergonic energy 21. Oxidative phosphorylation differs from substrate level phosphorylation in that: a. Oxidative phosphorylation is the synthesis of ATP in the Respiratory Chain b. Substrate level phosphorylation produces a P/O ratio of 3/1 in the mitochondria c. Oxidative phosphorylation takes place exclusively in the cytosol d. Substrate level phosphorylation is more energetically substantial to the cell 22. Which complex of the Electron Transport Chain does NOT yield energy when electrons flow through the ETC? a. NADH- CoQ dehydrogenase c. Cytochrome bc1 oxidase b. FMN CoQ dehydrogenase d. Cytochrome aa3 oxidase 23. The most common form of covalent modification that affects the activity of enzymes: a. Attachment of an adenylyl moiety c. attachment of a phosphate group b. Attachment of an acetyl group d. attachment of a sulfur atom 24. Which of the following is NOT classified as a peptide hormone? a. Insulin b. testosterone c. calcitonin d. ACTH 25. Which a. b. c. d.

of the following is TRUE regarding the insulin hormone Composed of 3 chains: A, B and C chains Its release is mediated by decrease in plasma glucose concentration Promotes entry of glucose into skeletal muscle cells and lipogenesis in adipose cells Stimulates gluconeogenesis by increasing the amount of phosphoenolpyruvate carboxykinase (PEPCK)

26. Characteristics of Primary Adrenal Insufficiency that differentiates it from Secondary Adrenal Insufficiency:

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a.

b.

Hypoglycemia Increased skin pigmentation

c. intolerance to stress d. decreased ability to excrete water load

27. The form of androgen produced in the adrenals of both males and females: a. Androstenedione b. testosterone c. androsterone

d. dihydrotestosterone

28. The adenylate cyclase and phosphoinositide cascades are signal transduction mechanisms associated with one of the following cell surface receptors: a. Receptor tyrosine kinase b. Ligand-gated ion channel

c. G protein-coupled d. cytokine family

29. Which digestive enzyme system is largely responsible for the breakdown of maltase in the intestinal tract? a. α-amylase b. glucoamylase c. sucrase-isomaltase d. trehalase 30. The first irreversible reaction of hepatic glycolysis is catalyzed by this enzyme: a. Glucokinase b. phosphofructokinase c. hexokinase d. pyruvate kinase 31. The oxidized phosphorylated form of the coenzyme NAD is a requirement for the optimum activity of this important enzyme of HMP: a. Transketolase c. transaldolase b. Epimerase d. glucose 6-PO4 dehydrogenase

32. The liver is able to perform its important task to maintain the normal blood glucose level because of the presence of this enzyme within its cells: a. Fructose 1,6 BisPO4tasec. pyruvate carboxylase

b.

PEP carboxykinase

d. glucose 6-PO4tase

33. Vitamin C is an essential nutrient for humans because of the absence of this enzyme of the uronic acid pathway: a. L-gulanolactone oxidase c. phosphoglucomutase b. UDPGlc pyrophosphorylase d. UDPGlc dehydrogenase 34. Increased secretion of glucagons causes increased blood glucose level because of the following, EXCEPT: a. Active hepatic glycogen phosphorylase is formed b. Phosphofructokinase-1 is down-regulated c. Inactive liver glycogen phosphorylase is formed d. Glycogen synthase is converted to the inactive form 35. True of glycogen synthesis: a. Requires glucose 6-PO4 b. Involves addition of activated glucose residues to glycogenin c. Stimulated by cAMP d. Glucosyl residues are added to the reducing ends of glucose polymers 36. This protein digestive enzyme of the pancreatic phase is activated by trypsin by releasing two dipeptides: a. Pepsinogen b. chymotrypsinogen c. proelastase d. procarboxypeptidase 37. The most common reaction involved in the removal of amino acid nitrogen from the body is by: a. Transamination reaction b. Hydrolytic deamination by asparaginase c. Oxidative deamination by glutamate dehydrogenase d. Dehydrative deamination of serine 38. TRUE of Urea Cycle EXCEPT for this one: a. Initiated in the mitochondria of the liver b. Stimulated with N-acetyl glutamate acting as the allosteric activator of CPS I c. Used to dispose ammonia through the formation of urea d. Inhibited during starvation by repression of the urea cycle enzymes

39. All of the following amino acids can react as substrates for gluconeogenesis EXCEPT: a. Arginine b. cysteine c. leucine d. methionine 40. This amino acid is important for inter tissue nitrogen transport: a. Glutamic acid b. alanine c. aspartic acid d. tyrosine

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41. Ammonia is toxic to the brain for this reason: a. Depletion of glutamine in the brain b. Shifts glutamate dehydrogenase equilibrium towards alpha ketoglutarate c. It favors increase synthesis of the inhibitory neurotransmitter – GABA d. Shifts glutamate dehydrogenase equilibrium towards glutamate and depletes the brain of alpha ketoglutarate. 42. TRUE of hormone control over amino acid metabolism: a. Thyroid hormone increases the sensitivity of target cells to insulin effects b. Cortisol and epinephrine stimulate amino acid synthesis through induction of enzymes c. Insulin promotes uptake of amino acids & protein synthesis in the muscle d. Glucagons favors gluconeogenesis, ureagenesis & protein synthesis 43. Digestive products of the action of pancreatic lipase on dietary lipids: a. 1 free fatty acid and diacylglycerol c. cholesterol and 1 free fatty acid b. 2 free fatty acids and monoacylglycerol d. phosphatidic acid and 1 free fatty acid 44. Degradation of even numbered fatty acids by B-oxidation: a. Provides propionyl CoA as an end product b. Generates more ATPs than the Krebs cycle c. Takes place in the cytosol simultaneously with fatty acid synthesis d. Yields palmitic acid only during fasting 45. Which process characterizes lipid metabolism in the fed state? a. Rapid utilization of ketone bodies by the extra-hepatic tissues b. Accelerated rate of fatty acid degradation c. Increased fatty acid and triacylglycerol synthesis in the adipose. d. Inhibition of acetyl CoA carboxylase required for ATP production. 46. In the biosynthesis of cholesterol, the rate limiting reaction catalyzed by which enzyme is best inhibited to decrease cholesterol synthesis: a. B-hydroxy B-methyl glutarylCoA reductase c. mevalonic acid kinase

b.

Squalene synthase

47. A principal end product of cholesterol catabolism: a. Acetoacetic acid b. coprostanol

d. Geranyl pyrophosphate synthase

c. cholic acid

d. cholestanol

48. Which of the following lipoproteins transports cholesterol from peripheral tissues to the liver (reverse cholesterol transport)? a. Chylomicron c. high density lipoprotein b. Low density lipoprotein d. very low density lipoprotein 49. In the degradation of glycerophospholipids, which enzyme will result in the release of unsaturated fatty acids like arachidonic acid? a. Phospholipase A1 b. Phospholipase A2 c. phospholipase C d. phospholipase D 50. Which of the following statements is TRUE as far as pharmacologic agents affecting eicosanoids are concerned? a. Because of its anti-inflammatory effects, acetaminophen is considered to be a true NSAID b. Aspirin is effective in inflammatory conditions brought about by excessive production of prostaglandins and leukotrienes c. Corticosteroids re effective in mitigating the effects of eicosanoids synthesized via the cyclooxygenase and lipooxygenase pathways d. Acetaminophen has few side effects because it is a selective COX-2 inhibitor 51. Nitric oxide diffuses through the cell membranes and travels from the endothelium to the smooth muscle to penetrate into the cell and bind: a. Guanylate cyclase b. arginine c. acetylcholine d. calmodulin 52. During an overnight fast, acceptable blood glucose levels are maintained by: a. Glycogenesis b. glycogenolysis c. lipogenesis d. proteolysis 53. In uncontrolled adult-onset diabetes mellitus, weight loss is caused by: a. Deposition of triacylglycerols in adipose tissues b. Failure to synthesize glucose in the liver

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c. d.

Loss of appetite from lack of insulin activity Mobilization of tissue protein for energy generation

54. In cancer cells, glycolysis is the prominent metabolic pathway, making them highly dependent on this fuel: a. Amino acids b. ethanol c. glucose d. fatty acids 55. Formation of this complex signals the activation of the final common pathway of the coagulation system: a. Tenase complex c. prothrombinase complex b. Contact phase complex d. fibrin polymerization 56. α1 antitrypsin is a plasma protein that protects the lungs from inflammatory damage by: a. binding to extracorpuscular hemoglobin b. binding to cytokines and targeting them to specific tissues c. inhibiting leucocyte proteases d. facilitating iron and copper transport 57. The portion of an immunoglobulin molecule that binds complement is the: a. Disulfide bridge b. Fab fragment c. Fc fragment

d. hinge region

58. Which class of immunoglobulin crosses the placenta and provides immunity to the fetus and the newborn? a. IgA b. IgD c. IgG d. IgM 59. The complement pathway is concluded by the destruction of the target cell by the: a. Activated mannan-binding lectin c. membrane attack complex b. C1qrs recognition unit d. union of factors B, D, and P 60. This ancillary pathway in red blood cell metabolism uses NADPH as a cofactor in the reduction of oxidized glutathione (GSSG): a. Embden-Meyerhof Pathway c. Methemoglobin Reductase Pathway b. Pentose Phosphte Pathway d. Leubering-Rapoport Shunt

61. In Pre Hepatic Jaundice cause by hemolytic anemia, the following is markedly increased: a.

b.

Direct or conjugated bilirubin Direct or unconjugated bilirubin

c. indirect or conjugated bilirubin d. indirect or unconjugated bilirubin

62. Which component of hemoglobin is responsible for its biological function of oxygen transport? a. Globin chains b. heme c. central cavityd. carboxy termini 63. Hemoglobin is more efficient oxygen transporter than myoglobin because hemoglobin: a. Displays positive cooperativity when binding oxygen b. Can bind oxygen even when the pO2 is low c. Promotes the formation of oxyhemoglobin in the capillaries d. Releases oxygen in exchange for CO2 in the alveolar capillaries

64. Carbon dioxide produced from metabolic processes is transported in the blood predominantly in this chemical form: a. Carboxyhemoglobin

b. bicarbonate

65. A major cellular generator of ROS: a. Krebs cycle b. mitochondrial ETC pathway

c. carbaminohemoglobin

c. anaerobic glycolysis

d. carbon monoxide

d. pentose phosphate

66. Lipid peroxidation is initiated when: a. Tocopherol is recycled by ascorbate. b. Glutathioine peroxidase detoxifies the fatty acid chain c. A free radical attacks a double bond of PUFA d. Ascorbate is recycled by phospholipase 67. The products of the type of glycolysis predominant in the cortical areas of the nephron: a. 2 pyruvate, 2NADH + H. 2 ATPs c. 2 lactate, 2 NAD+, 2 ATPs

b.

2 pyruvate, 2 NAD+, 4 ATPs

d. 2 lactate, 2 NAD+, 4 ATPs

68. 45% of the total CO2 formed in the normal physiological state comes from: a. Glutamine b. lactate c. fatty acids d. glucose 5

69. The Z DNA Helix: a. Is inhibited by the methylation of the bases b. Is a permanent conformation of DNA c. Has a fewer base pairs per turn than the B DNA d. Is favored by the alternating GC Sequences

70. This nucleoside is present in DNA and not in RNA: a. Adenosine b. deoxyguanosine c. deoxycytidine

d.deoxythymidine

71. Which of the following enzymes regulates the rate-limiting and committed step in the de-novo synthesis of purines? a. Xanthine oxidase b. Glutamine PRPP amidotransferase c. Hypoxanthine-guanine phosphoribosyl transferase d. Adenine phosphoribosyl transferase 72. All of the following can lead to the accumulation of uric acid in hyperuricemia and eventually leading to gout, EXCEPT: a. Elevated activity of PRPP synthetase, which may result from insensitivity to feedback inhibition by purine nucleotides b. Deficiency of the enzyme hypoxanthine-guanine phosphoribosyl trnasferase c. Mutations in PRPP amidotransferase that render it less sensitive to feedback inhibition by purine nucleotides d. Deficiency of xanthine oxidase due to a genetic defect or to severe liver damage 73. TRUE of DNA Polymerases: a. Use dsDNA as template for synthesis of DNA b. Enzyme used in the synthesis of RNA primer in the leading strand c. Have 5’ to 3’ polymerization activity d. Recognize nucleotide sequences in the template DNA before the start of replication

74. The first base to be (copied ?) is located: a. b. c. d.

Ten bases downstream from the Pribnow Box Twenty five bases upstream from the Hogness Box At the coding strand of the dsDNA At the non-template strand of the dsDNA

75. Translation will require the following, EXCEPT: a. Triplet codon found in the mRNA c. ribosomes b. Anticodon carried by the tRNA d. template DNA

76. In the LAC operon, the repressor binds to this site to inhibit transcription of the structural genes: a. Promoter site c. operator site b.

Attenuator site

d. CAP site

77. Which base substitution exemplifies transition mutation? a. CA b. G  C c. AG d. T  A 78. To prevent permanent genetic change, the best time to repair a mutation is: a. Before the next replication c. following transcription b. During translation d. for the duration of the S phase 79. Prevents entry of damaged DNA into the cell cycle to protect the genome from excessive mutations: a. M-Cdk b. p53 c. erb d. fos 80. A way by which the organism can delete cells with DNA damage to prevent carcinogenesis and render the damage harmless: a. Apoptosis b. metastasis c. oncogenesis d. angiogenesis 81. The ideal blot transfer technique for DNA is the: a. Northern blot b. Southern blot c. Southwestern blot

d. Western blot

82. Taq polymerase is most commonly used in PCR because this enzyme: a. Halts DNA synthesis at very low temperatures

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b. c. d.

Is able to tolerate very high temperatures Hybridizes primers with extreme ease Elongates daughter strands in the absence of a primer

83. Which a. b. c. d.

of the following is NOT TRUE regarding xenobiotic metabolism: Involves the elimination of foreign and undesirable compounds from the body Is synonymous with the term ‘detoxification’ Occurs mostly in the major organ of metabolism, which is the liver Predominantly involves the Cytochrome P450 enzyme system

84. Which a. b. c. d.

of the following is TRUE regarding Cytochrome P450 system? Has a limited number of isoforms Requires NADH for its reduction and thus efficacy Exhibits polymorphism resulting to inter-individual differences in drug responses Is not inducible owing to the consistency of its activity

85. Cross-links between tropocollagen molecules involving two allysine residues: a. Schiff base formation c. Van der Waals interactions b. Hydrogen bonding d. aldol condensation 86. One of a. b. c. d.

the characteristics of elastin that differentiates it from collagen: Quarter-staggered array of its fibers About 1/3 of its amino acid composition is glycine Does not contain modified amino acids like hydoxylysine Cross-linking between fibers involving the formation of a Schiff’s base

87. Although the brain cannot use this for ATP production; it is actively involved in its metabolism evidenced by intracellular concentrations higher than that in the liver: a. Glucose b. amino acids c. fatty acids d. glycogen 88. Which a. b. c. d.

is true of the brain’s metabolism? Consumes 20% of oxygen and 60% glucose utilization at rest Normally uses ketone bodies as energy source Fatty acids are alternative source for energy generation Amino acids can be used for gluconeogenesis

89. During the cycle of muscle contrction-relaxation, binding of ATP to the S-1 head of myosin promotes the: a. Dissociation of actin from myosin resulting in muscle relaxation b. Persistent attachment of actin to myosin leading to rigor mortis c. Increased concentration of Ca+2 in the sarcoplasm necessary for contraction to occur d. Development of the power stroke responsible for the onset of muscle ischemia 90. Which statement is true regarding bone remodeling? a. Increased density of normal bone is achieved by inhibition of bone resorption by osteoclasts. b. A balance of bone resorption by osteoclasts and bone deposition by osteoblasts is necessary to maintain bone integrity. c. Balanced bone remodeling requires an overexpression of osteoclastic activity. d. Osteoporosis is the end result of continuing cycles of remodeling, consisting of resorption followed by deposition of a new bone tissue.

91. This association of transducin and the regulatory subunits of PDE of cones exposes the two α, catalytic subunits of the latter: a. α GTP yy b. α

GTP

αα

c. α

GDP

βy

d. α GDP αβ

92. The characteristic primary odor of onion, garlic and leeks: a. Floral b. putrid c. malty d. pungent

93. A lectin expressed on the endothelium of small caliber blood vessels involved in the homing of white blood cells to sites of inflammation: a. Siglec b. collectin

c. annexin

d. selectin

94. All of the following are correct statements regarding biochemistry of aging EXCEPT: a. Free radicals contribute to oxidative stress that accelerates aging. b. The shorter the telomeres are, the shorter the life span of the species. c. Stability of DNA and efficiency of repair system correlate positively with longevity of species. d. Advanced glycation end products (AGEs) prolong the life span of cellular proteins and retard aging

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95. In order for a high fiber diet to be useful and not cause complications, it should be come with: a. A generous fluid intake c. a liberal intake of dietary fat b. An increase in physical activity d. longer hours between meals 96. Coconut oil is considered a “good fat” because its benefits that are ascribed to a significant content of: a. Monounsaturated fat b. lauric acid c. trans-fat d. cholesterol 97. Iron supplements are best taken with ascorbic acid because: a. Vitamin C forms chelate that keep iron soluble b. Vitamin C keeps iron in the ferric form for better absorption c. Ascorbic acid facilitates binding of iron to mucosal transferring d. Ascorbic acid precipitates iron in the stomach to be efficiently absorbed 98. Laboratoy findings found in Iron Deficiency Anemia: a. Macrocytic, hyperchromic RBCs in peripheral smear b. Hemoconcentration c. Increased total iron binding capacity d. Decreased serum transferring saturation 99. TRUE regarding the clinical manifestations of marasmus patients: a. Edema is the cardinal sign c. hair sign like “flag sign” are common b. Anemia commonly present d. presence of old man’s facies and winged scapulae 100.The form of Vitamin A that reaches its target tissue like the retina: a. Retinol b. retinyl esters c. retinoic acid

d. 11-cis-retinal

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