Test Yourself

Test Yourself Test Yourself

1. The peptide bonds after positively charged amino acids are cleaved by? a. Cyanogen bromide b. Chymotrypsin c. Trypsin d. Asp-N-protease

2. Deficiency of which of the following enzymes leads to reduction in sperm production? a. Vitamin A b. Vitamin D c. Vitamin E d. Vitamin K

3. The conversion of Fructose-6-phopshate to Fructose-1,6-bisphosphate is catalyzed by which one of the following enzymes? a. Phosphofructokinase 1 b. Phosphofrucokinase 2 c. Fructose-1,6-Bisphosphatase-1 d. Fructose-1,6-Bisphosphatase-2

4. Coenzyme Q is directly involved in electron transport chain as: a. a water soluble electron donor b. a lipid soluble electron donor c. a covalently attached cytochrome cofactor d. directly to oxygen

5. The terminal electron acceptor during mitochondrial respiration: a. H2O b. NAD+ c. ATP d. O2

6. Cytochrome oxidase contains which of the following metal ions, as co-factor? a. Co b. Mg c. Fe d. Hg

7. Crystalline substances dissolve more easily in water because of? a. increase in entropy as the crystal lattice is distorted b. increased electrostatic interaction between water and charged molecules c. decreased electrostatic interaction d. both a and b

8. The macromolecule structure and function is stabilized as result of these kinds of interaction except one: a. Van-der Walls interaction b. Covalent interaction forces c. Hydrogen bonding d. Electrostatic forces of interactions

9. Which among the following is true about the properties of aqueous solution? a. A pH changes from 5.0 to 6.0 reflects an increase in the hydroxide ion concentration (OH-) of 20% b. A Ph change from 8.0 to 6.0 reflects a decrease in the proton concentration (H+) by a factor of 100 c. Charged molecules are generally insoluble in water d. Hydrogen bonds form readily in aqueous solution

10. The enzyme fumarase catalyzes the reversible hydration of fumaric acid to L-malate, but it will not catalyze the hydration of maleic acid to the cis isomer of fumaric acid. This is an example of a. Biological activity b. Racemization c. Stereoisomerization d. Stereospecificity

11. Calculate the molarity of an NaOH in a solution prepared by dissolving 2 grams in water to form 250 mL of the solution. a. 0.2 M b. 0.4 M c. M d. 0.8 M

12. Which amino acid will frequently plot in the disallowed region of Ramachandran plot? a. proline b. Glycine c. Alanine d. Glutamine

13. The proline derivative 4-hydroxyproline plays an essential role in folding of collagen and maintaining its structure. The deficiency of which of the following vitamins will lead to a distorted protein folding: a. Vitamin A b. Vitamin D c. Vitamin C d. Vitamin B

14. A protein has got disulphite linkages. The native protein with intact disulphide linkages is cleaved into small peptides. Which technique can be used for the detection of the number of cysteine residues joined by disulphide linkages? a. MALDI b. FAB-MS c. Gas-chromatography-MS d. X-ray crystallography

15. In a mixture the presence of glycoproteins can be most efficiently determined by which of the following components a. Ninhydrin b. Coomassie blue c. Lectin d. Silver nitrate

16. Myoglobin and hemoglobin have very: a. different primary and tertiary structures b. similar primary and tertiary structures c. similar primary structures but different tertiary structures d. similar tertiary structures but different primary structures

17. Isozymes are: a. enzymes that differ in amino acid sequences b. the are formed from different alleles of same gene c. that are products of different genes d. both (a) and (c)

a. Competitive inhibition b. Uncompetitive inhibition c. Mixed inhibition d. Noncompetitive inhibition

19. Which among the following has got highest bond dissociation energy? a. C=O b. C=N c. C=C d. C-C

20. The alpha-helix is stabilized by: a. Hydrogen bonds b. Vander-waal’s interactions c. Covalent bonds d. Ionic bonds

21. A solution was prepared by mixing NaOH & agar with distilled water. Which of the following species will contribute to changes in pH? a. NaOH b. Distilled water c. Agar d. Both NaOH and agar

22. What is the effect of adding CaOH)2 is added to distilled water at pH-7? a. pH will change to 8 b. pH will change to 6 c. pH will not change d. pH range of 6 to 7 will be maintained

23. A buffer was prepared by mixing HCl & NaOH. Both the species will help in the formation of conjugate acid base pair. Which of the following will act as conjugate acid- base pair to maintain the buffering range? a. H+ + OH- , H2O b. NaCl, H+ + Clc. Both a & b d. The buffer cannot be made using HCl & NaOH

24. The temperature of the system .decreases in an a. adiabatic compression b. isothermal expansion c. isothermal compression d. adiabatic expansion

25. In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can be best described as: a. Hyperbolic b. Linear with a negative slope c. Linear with positive slope d. Sigmoidal

26. The hydrolysis of ATP has a large negative ∆G'°; nevertheless it is stable in solution due to: a. entropy of stabilization b. ionization of phosphate c. resonance stabilization d. the hydrolysis reaction has a large activation energy

27. Why Uracil is present only in RNA and not in DNA? a. It is bulky then Thymine, affecting DNA stability b. Uracil can easily convert to Cytosine, causing frame shift in DNA c. Uracil forms 3 hydrogen bonds, hence cannot bind to Adenine in DNA d. Uracil can easily convert to Cytosine, causing base transition.

28. The DNA duplex absorbs 40% less UV rays than individual bases. Which of the following statement can be a reasonable explanation for the above statement? a. The duplex formation diminishes the capacity of bass to absorb due to base stacking. b. The duplex has major and minor grooves c. The individual bases show different chemical property than that of Duplex form d. The duplex is present inside the nucleus, where as individual bases in nucleotide pool of cytoplasm

29. Topoisomerases can cut and re knot the DNA strands. They break the phosphodiester bond between 2 adjacent bases. Surprisingly they do not use ATP hydrolysis energy to cleave the high energy Phosphate bond. What may be a possible explanation for this peculiar behavior? a. The total ATP used to cleave the bond, is regenerated at the end of the reaction, hence net ATP is used is Zero. b. The phospho diester bonds are not high energy bonds c. They pull the adjacent bases apart, thus breaking the bond d. Topoisomerases form phospho-tyrisine bond, which conserves the energy , that is used to form the ester bond to rejoin the DNA

30. Ethidium Ions cause DNA to unwind. They are florescent under UV radiation and used extensively in DNA mobility studies. They intercalate the DNA chaging the normal rotation of base pairs from 36° to 10°. If you happen to add one ethidium ion between every 2 bases of DNA, how many bases you will find in per turn of the helix? a. 36 b. 72 c. 10 d. 5.5

31. DNA and RNA are the nucleic acids differing in only one OH- group. The DNA forms major genetic material and RNA , the messenger role and catalytic roles. The trans-esterification reaction involves formation of esters in the ribose sugar. What may be the reason, that this reaction is specific for only RNA , but not DNA. a. The esterase enzymes are present in the nucleus, where as DNA is present in the nucleus. b. The DNA has 3’–Phosphate groups which will not allow trans esterification c. The DNA has no 3’ OH group which is necessary for transesterification d. The DNA has no 2’OH- group which is necessary for transesterification

32. A non supercoiled B-DNA molecule is composed of 4800bps. How many helical turns are present? a. 10 b. 380 c. 480 d. Impossible to determine

33. If RNA in TMV contain 28% cytosine then what percentage of the bases in TMV are adenine?? a. 30% b. 20% c. 60% d. Cannot be determined

34. Where would you expect a polypeptide region that is rich in the amino acids valine, leucine and isoleucine to be located in the folded polypeptide? a. Interior of polypeptide b. Exterior of polypeptide c. In the active site of globular proteins d. In the DNA degrading ezzyme complex

Unit 1 35. Enzymes that break down the DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes? a. the two strandes of the double helix would separate b. the phosphodiester linkages of the polynucleotide backbone would be broken. c. The purines would be separated from the deoxyribose sugars d. All bases would be separated from the deoxyribose sugar

36. Which one of the following is the correct order of electron transfer in ETC a. Cytochrome-b; Cytochrome-c; Cytochrome c1; cytochrome (a+a3); Coenzyme Q; Cytochrome b b. CoenzymeQ; Cytochrome b; Cytochrome C1; Cyrochrome c; Cytochrome (a+ a3) c. Cytochrome (a + a3); Cytochrome b; Cytochrome c; Cytochrome C1; Coenzyme Q d. None of the above

37. A person is suffering with cancer. The anticancer drug that has been designed has got to ability to inhibit the uncontrolled glycolytic pathway. Iodoacettae has been used in the treatment. IAA is known as an irreversible inhibitor of all cysteine proteases. Which particular step in glycolysis will be affected upon treatment with IAA? a. The conversion of 3-phosphoglycerate to 2-phosphoglycerate b. The conversion of Glyceraldehyde -3-phosphate to 3-phosphoglycerate c. The conversion of 1,3 Bisphosphoglycerate to 3-phosphoglycerate d. Phosphoenolpyruvate to Pyruvate

38. In the first step of glycolysis, the enzyme hexokinase uses ATP to transfer a phosphate to glucose to form glucose-6-phosphate. The product continues to be oxidized forming pyruvate in glycolysis and is a precursor to acetyl-CoA for the citric acid cycle. Suppose that a cell has only glucose available for energy and that the activity of hexokinase is suddenly stopped in this cell. Which of the following conditions will occur? a. The cell will continues to produce energy from mitochondrial electron transport chain b. The cell will continue producing ATP using citric acid cycle c. The cell will ultimately be unable to produce ATP d. The cell will be forced to switch to fermentation to produce ATP

39. During a heart attack, blood flowing to the heart muscle is interrupted by blockage of a coronary artery. Which among the following statement is incorrect with respect to change in metabolism in the heart? a. oxidative phosphorylation would slow down in the mitochondria b. the production of water by mitochondria will be increased c. the rate of production of lactic acid would be stimulated d. the use of glucose by the muscle tissue would increase

40. If you isolate mitochondria and place them in buffer with a low pH they begin to manufacture ATP. Which of the following can be a satisfactory explanation for this behavior? a. Low pH increases the concentration of base causing mitochondria to pump outH+ to the inter membrane space leading to ATP production. b. The high external acid concentration causes an increase in H+ in the inter membrane space leading to increased ATP production by ATP synthetase. c. Low pH increases the acid concentration in the mitochondrial matrix, a condition that normally causes ATP production. d. Low pH increases the OH- concentration in the matrix resulting in ATP production by ATP synthetase

41. Collagen has evolved to provide strength. It is found in connective tissue such as tendons, cartilage, the organic matrix of bone and cornea. The collagen helix is a unique secondary structure quite distinct from the alpha-helix. Which of the following statements is incorrect with respect to collagen structure a. they contain about 35% glycine, 11% alanine and 21% praline and 4-hydroxyproline b. three separate polypeptide chains called as alpha chains are supertwisted around each other c. It is rich in hydrophobic residues like Alanine, valine, leucine, methionine d. It is left handed and has three amino acid residues per turn

42. Which among the following graph will best represent the ramachandran plot for alanine?

c d

43. The tabulated data given here indicates the results of an enzymatic assay carried out under two different experimental conditions. The value of Vmax and Km for both sets of conditions are: a. Conditon A: Vmax = 0.28 and Km = 0.42; Condition B: Vmax = 0.36 and Km = 0.52 b. Condition A: Vmax = 0.42 and Km = 0.28; Condition B: Vmax = 0.52 and Km = 0.36 c. Condition A: Vmax = 0.42 and Km = 1.1; Condition B: Vmax = 0.52 and Km = 1.1 d. Condition A: Vmax = 0.40 and Km = 2.0; Condition B: Vmax = 0.51 and Km = 2.0

44. Consider an enzymatic conversion as shown below,

The rate of formation of [ES] complex is 1.5 * 10-5 M-1 s-1, the rate of dissociation of [ES] complex to [E] and [S] is 4.6 * 10-6 s-1, and formation of product is the rate limiting step. The Km for this reaction is a. 1 M b. 5 mM c. 2.5 mM d. 0.2 M

45. The graph shown below indicates reaction rates versus substrate concentration for three different enzymes. Identify which curve corresponds to which of the three different enzymes. a. A= Michaelis Menton; B = Allosteric dimer; C = Allosteric octamer b. A= Allosteric dimer; B = Michaelis Menton; C = Allosteic octamer c. A = Allostertic octamer; B = Allosteric dimer; C = Michaelis Menton d. A = Allosteric dimer; B = Allosteric octamer; C = Michaelis Menton

46. The conversion of phosphoenol-pyruvate to pyruvate is highly favourable and is an example of substrate level phosphorylation. The free energy of hydrolysis of phosphoeneol pyruvate is -61.9 kJ/mol. Which among the following statements best explains this observation? a. The product of hydrolysis is keto pyruvate, which quickly tautomerizes to pyruvate. This keto- enol tautomerization stabilizes the products of hydrolysis relative to phosphoenolpyruvate, which cannot tautomerize. b. The product of hydrolysis is enol pyruvate, which quickly tautomerizes to pyruvate. This keto- enol tautomerization stabilizes the products of hydrolysis relative to phosphoenolpyruvate, which cannot tautomerize.

Unit 1 c. The product of hydrolysis is enol pyruvate, which does not quickly tautomerizes to pyruvate. This keto- enol tautomerization stabilizes the products of hydrolysis relative to phosphoenolpyruvate, which cannot tautomerize. d. The product of hydrolysis is enol pyruvate, which quickly tautomerizes to pyruvate. This keto- enol tautomerization does not stabilizes the products of hydrolysis relative to phosphoenolpyruvate, which cannot tautomerize.

47. Insulin is a peptide hormone produced in the pancreas by beta cells. It aims to lower the glucose level in blood and is normally secreted after every meal. Their action is to activate transporters of glucose found on the surface of the cells, so that the cells can take up glucose from blood and into cells. What glucose transporter is regulated by the action of insulin? a. Sodium-Glucose transporter (SGLT) b. Glucose transporter2 (GLUT 2) c. Glucose transporter 5 (GLUT 5) d. Glucose transporter 4 (GLUT 4)

48. Which among the following statements in incorrect about myoglobin the oxygen carrying molecule in muscles? a. It is a single polypeptide chain made up of 153 amino acids b. The interior consists of myoglobin consists of nonpolar residues such as leucine, valine, methionine, phenylalanine c. Histidine residue plays a crutial role in binding iron and oxygen d. They consist of many charged residues like aspartate, glutamate, lysine, arginine

49. The first step in two-dimensional gel electrophoresis generates a series of protein bands by isoelectric focusing. In a second step, a strip of this gel is turned 90 degrees, placed on gel containing SDS, and electric current is applied. In this second step: a. proteins with similar isoelectric points become further separated according to their molecular weights b. the visual bands become stained so that the isoelectric focus pattern can be visualized c. the individual bands become visualized by interacting with protein-specific antibody in the second gel d. the protein in the bands separate more completely because the second electric current in the opposite polarity to the first current

50. In the diagram below, the plane drawn behind the peptide bond indicates:

a. plane of raotation around Cα-N bond b. region of steric hindrance determined by the large C=O group c. absence of rotation around the C-N bond because of its partial double-bond character d. theoretical space between -180 and +180 degrees that can be occupied by the φ and ψ angles in the peptide bonds

51. Experiments on denaturation and renaturation after the reduction and reoxidation of the –S-S- bonds in the enzyme ribonuclease (RNase) have shown that: a. the completely unfolded enzyme, with all –S-S- bonds broken, is still enzymatically active b. the enzyme, dissolved in water, is thermodynamically stable relative to the mixture of amino acids whose residues are contained in RNase c. the primary sequence of RNase is sufficient to determine its specific secondary and tertiary structure d. native ribonuclease does not have a unique secondary and tertiary structure

52. Which of the following statements about the glycerol-phosphate/malate-aspartate shuttles is true? a. The glycerol-phosphate shuttle transports NADH across the outer mitochondrial membrane, while the malate-aspartate shuttle transports NADH across the inner mitochondrial membrane b. The malate-aspartate shuttle is a less energy-efficient means of transporting metabolites across the mitochondrial membrane c. FAD serves as the oxidizing agent in the mitochondrial matrix with the glycerol-phospate shuttle. d. None of these are true

53. Dinitrophenol is an inhibitor that decreases the production of ATP by a. incorporating into the inner mitochondrial membrane thereby making the membrane permeable to protons b. binding a proton on the acidic side of the membrane, diffusing through the membrane, and releasing the proton on the alkaline side of the membrane. c. binding to the T state of F1 of ATP synthase thereby inhibiting the conformational change necessary to form ATP d. stimulating proton flux through the uncoupling protein, thermogenin.

Unit 1 54. Both water and glucose share an -OH that can serve as a substrate for a reaction with the terminal phosphate of ATP catalyzed by hexokinase. Glucose, however, is about a million times more reactive as a substrate than water. The best explanation is that: a. the larger glucose binds better to the enzyme; it induces a conformational change in hexokinase that brings active-site amino acids into position for catalysis. b. water normally will not reach the active site because it is hydrophobic c. water and the second substrate, ATP, compete for the active site, resulting in a competitive inhibition of the enzyme d. the -OH group of water is attached to an inhibitory H atom while the glucose -OH group is attached to C

55. Lysozyme has a pH centered around pH 5.0. The active site of lysozyme contains a glutamic acid residue (pKa = 5.5) and an as partic acid residue (pKa = 4.0). Which of the following statements is correct about the mechanism of lysozyme? a. The glutamic acid residue is in a more polar environment than the aspartic acid. b. During the entire catalytic mechanism, the aspartic acid residue remains unprotonated. c. During the mechanism, an oxyanion transition state forms. d. The glutamic acid residue acts as a general base catalyst.

56. A nonapeptide was determined to have the following amino acid composition: (Lys)2,(Gly)2,(Phe)2,His,Leu,Met. The native peptide was incubated with 1-fluoro-2,4-dinitrobenzene (FDNB) and then hydrolyzed; 2,4-dinitrophenylhistidine was identified by HPLC. When the native peptide was exposed to cyanogen bromide (CNBr), an octapeptide and free glycine were recovered. Incubation of the native peptide with trypsin gave a pentapeptide, a tripeptide, and free Lys. 2,4-Dinitrophenylhistidine was recovered from the pentapeptide and 2,4-Dinitrophenylphenylalanine was recovered from the tripeptide. Digestion with the enzyme pepsin produced a dipeptide, a tripeptide and a tetrapeptide. The tertrapeptide was composed of (Lys)2, Phe and Gly. The native sequence was determined to be: a. Gly-Phe-Lys-Lys-Gly-Leu-Met-Phe-His b. His-Phe-Leu-Gly-Lys-Lys-Phe-Met-Gly c. His-Leu-Phe-Gly-Lys-Lys-Phe-Met-Gly d. His-Leu-Gly-Lys-Lys-Phe-Phe-Gly-Met

57. Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid. Based on this information, which of the following is correct? a. Succinate dehydrogenase is the enzyme, and fumarate is the substrate. b. Succinate dehydrogenase is the enzyme, and malonic acid is the substrate. c. Succinate is the substrate, and fumarate is the product. d. Fumarate is the product, and malonic acid is a noncompetitive inhibitor.

58. Protein kinases are enzymes that catalyze phosphorylation of target proteins at specific sites, whereas protein phosphatases catalyze removal of phosphate(s) from phosphorylated proteins. Phosphorylation and dephosphorylation can function as an on-off switch for a protein's activity, most likely through a. the change in a protein's charge leading to a conformational change. b. the change in a protein's charge leading to cleavage. c. a change in the optimal pH at which a reaction will occur. d. a change in the optimal temperature at which a reaction will occur.

59. Which amino acid residue is most likely to be found in the interior of a water soluble globular protein? a. Ser b. Val c. Arg d. Asp

60. Which of the following statements about protein secondary structure is correct? a. An alpha-helix is primarily stabilized by ionic interactions between the side chains of the amino acids b. Beta-sheets exist only in antiparellel form c. Beta-turns often contain proline d. An alpha-helix can be composed of more than one polypeptide chain.

61. Given below are four enzymatic reactions involved in glycolysis. In which of the following steps is ATP generated? a. 2-phosphoglycerate to phosphoenol pyruvate

Unit 1 b. Glucose-6-phosphate to fructose-6-phosphate c. Phosphoenol pyruvate to pyruvate d. Glyceraldehyde-3-phosphate to 1,3-bisphosglycerate.

62. Which of the following compounds is a positive allosteric regulator of the enzyme pyruvate carboxylase? a. ATP b. acetyl CoA c. Biotin d. PEP

63. Which one of the following sequences in proteins corresponds to N-glycosylation site? a. Asn-Ser/Thr b. Asn-X-Ser/Thr c. Asn-X-X-Ser/Thr d. Ser/Thr-Asn

64. Competitive inhibitors inhibit biochemical reactions in such a way as to seemingly: a. Increase the concentration of substrate. b. Reduce the concentration of enzyme. c. Increase the concentration of enzyme. d. Reduce the concentration of substrate. e. Denature the enzyme

65. Penicillin is a drug that acts by: a. Irreversibly inhibiting transpeptidase. b. Reversibly inhibiting transpeptidase. c. Competitively inhibiting transpeptidase. d. Noncompetitively inhibiting transpeptidase. e. None of these.

66. In proteins under normal physiological condition (pH =7) which of the following amino acids will be partially ionized? a. Arginie b. Lysine c. Histidine d. Serine

67. Active site of Topoisomerase I contains a. Tyrosine b. Tryptophan c. Glycine d. Fe+3 ions

68. R-groups in an α-helix: a. Extend outward from the central axis to avoid interfering stearically with each other b. Extend inward from the central axis c. Have to be close together to stabilize the helix d. Form the anti-parallel β-sheets e. Are hydrogen bonded to peptide bonds four amino acids away in the chain

69. Nonregular, nonrepetitive secondary structures a. Include α-helices and β-sheets b. Are bends, loops, and turns that do not have a repeating element c. Are beta-strands d. Are Beta-sheets e. Include beta-sheets

Unit 1 70. What is the axial ratio (length: diameter) of a viral DNA molecule 20μm long? a. 1 x 105 b. 1 x 104 c. 2 x 104 d. 2 x 105

71. Why RNA is hydrolyzed by alkali, whereas DNA is not? a. RNA has Uracil, unlike DNA b. The 2’deoxy sugar of RNA is more susceptible than 2’ oxy ribose of DNA c. The 2’deoxy sugar of DNA is less susceptible than 2’ oxy ribose of RNA d. The 2’ Deoxy ribose of DNA is not affected by alkali as DNA is present inside the Nucleus and wrapped by nucleosomes, so that no DNA is free for alkali action.

72. Which of the following statement is true? A. Chromosomes are membrane bound and are stable in entire life span of a cell. B. If barr body is formed in female, no genes form father will be expressed in the child. a. Only A b. Only B c. Both A and B d. None of these.

73. Calculate the specificity constant for an enzyme if its kcat = 1.4 x 104 s-1 Km = 90 µM. Is this enzyme very efficient? a. 16X 107, enzyme is not efficient. b. 16X107, enzyme is very efficient. c. 16X1010, enzyme is very efficient. d. 1.6X 1010, enzyme is not efficient.

74. Which of the following statements about the mechanism of the catalytic triad of chymotrypsin is correct? a. A proton moves from the serine to the histidine to the aspartate side chain in the catalytic triad of chymotrypsin. b. A proton moves from the aspartate to the serine to the histidine side chain in the catalytic triad of chymotrypsin. c. A proton moves from the serine to the histidine side chain in the catalytic triad of chymotrypsin. d. A proton moves from the aspartate to the histidine side chain in the catalytic triad of chymotrypsin.

75. Electromotive force (e.m.f) is a measure of charge of solution. When we dip a electrodes in solutions, they pick up some elec tric charges from the solution. The charge development depends on its pH content. In a saturated calomel electrode pH = [e.m.f - 0.246]/ 0.059. When the electrodes are dipped in a solution the voltmeter reads 0.652. What is the pH if the solution? a. 6.9 b. 6.0 c. 9.6 d. 0.69

76. A protein contains 2 Trp and 4 Tyr residues. The molecular mass of the protein is 17000D and that of Trp and Tyr are 204 and 18 0 D respectively. Values of E1%cm, the absorption coefficient of 1% (g/v) solutions of Trp and Tyr in 1-cm cell at 280 nm, are 269.60 and 83.33, respectively. The absorption of 1mg/ml protein solution in 1cm-cell at 280nm will be: a. 0.1 b. 1.0 c. 0.7 d. 1.7

77. -5, the entropy of the reaction has not changed, and the reaction is just a isomerization step. What is the enthalpy/ bond energy of the isomerization step? ( R = 8.314 J/mol.K ; T = 25C ) a. 24 KJ/mol b. 50Kj/mol c. 24 J /mol d. 0.24 kj/mol.

Unit 1 78. If a 0.1 M solution of glucose 1-phosphate is incubated with a catalytic amount of phospho- glucomutase, the glucose 1-phosphate is transformed to glucose 6-phosphate until equilibrium is reached. At equilibrium, the concentration of glucose 1-phosphate is 4.5 x 10–3 M and that of glucose 6phosphate is 8.6 x 10–2 M. What is the value of ∆G'° for this reaction?(in the direction of glucose 6-phosphate formation). (R = 8.315 J/mol•K; T = 298 K) a. –8.3 kJ/mol b. +7.3 kJ/mol c. –7.3 kJ/mol d. +8.3 kJ/mol

79. Which of the following graphs shows the results of reaction rate vs substrate concentration for an non-allosteric enzyme in the absence and presence of a non-competitive inhibitor (non-competitive inhibitors bind to an enzyme at a site different than the active site)?

a. 1 b. 2 c. 3 d. 4 e. none of the graphs.

80. When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. Which one of the following statements is most nearly correct, when applied to the reaction below (R = 8.315 J/mol•K and T = 298 K)? Glucose 6-phosphate ↔ fructose 6-phosphate a. ∆G'° is +1.7 kJ/mol. b. ∆G'° is –1.7 kJ/mol. c. ∆G'° is incalculably large and negative. d. ∆G'° is incalculably large and positive. e. ∆G'° is zero.

81. Given that the standard free energy change (∆G°) for the hydrolysis of ATP is –7.3 K cal/mol and that for the hydrolysis of Glucose 6-phosphate is –3.3 Kcal/mol, the ∆G° for the phosphorylation of glucose is Glucose + ATP → Glucose 6–Phosphate + ADP. a. –10.6 Kcal/mol b. –7.3 Kcal/mol c. –4.0 Kcal/mol d. +4.0 Kcal/mol.

82. For the following reaction, ∆G'° = +29.7 kJ/mol. L-Malate + NAD+  oxaloacetate + NADH + H+. The reaction as written: a. can never occur in a cell. b. can occur in a cell only if it is coupled to another reaction for which ∆G'° is positive. c. can occur only in a cell in which NADH is converted to NAD+ by electron transport. d. cannot occur because of its large activation energy. e. may occur in cells at some concentrations of substrate and product.

83. A drug which prevents uric acid synthesis by inhibiting the enzyme xanthine oxidase is a. Aspirin

Unit 1 b. Allopurinol c. Colchicine d. Probenecid

84. Lactate formed in muscles can be utilized through a. Rapoport-Luebeling cycle b. Glucose-alanine cycle c. Cori’s cycle d. Citric acid cycle

85. Which one of the following statements concerning glucose metabolism is correct? a. The conversion of Glucose to lactate occurs only in the R.B.C b. Glucose enters most cells by a mechanism in which Na+ and glucose are co-transported c. Pyruvate kinase catalyses an irreversible reaction d. An elevated level of insulin leads to a decreased level of fructose 2, 6-bisphosphate in hepatocyte

86. A ketogenic aminoacid is a. Valine b. Cysteine c. Leucine d. Threonine

87. In abetalipoproteinemia, the biochemical defect is in a. Apo-B synthesis b. Lipoprotein lipase activity c. Cholesterol ester hydrolase d. LCAT activity.

88. Conversion of inosine monophosphate to xanthine monophosphate is catalysed by a. IMP dehydrogenase b. Formyl transferase c. Xanthine-guanine phosphoribosyl transferase d. Adenine phosphoribosyl transferase

89. Methionine is synthesized in human body from a. Cysteine and homoserine b. Homocysteine and serine c. Cysteine and serine d. None of these

90. Hydroxylation of phenylalanine requires all of the following except a. Phenylalanine hydroxylase b. Tetrahydrobiopterin c. NADH d. Molecular oxygen

91. The amino acid that undergoes oxidative deamination at significant rate is a. Alanine b. Aspartate c. Glutamate d. Glutamine

92. All the following statements about phenylketonuria are correct except a. Phenylalanine cannot be converted into tyrosine b. Urinary excretion of phenylpyruvate and phenyllactate is increased c. It can be controlled by giving a lowphenylalanine diet

93. Acetyl CoA carboxylase regulates fatty acid synthesis by which of the following mechanism? a. Allosteric regulation b. Covalent modification c. Induction and repression d. All of these

94. β-Oxidation of fatty acids requires all the following coenzymes except a. CoA b. FAD c. NAD d. NADP

95. Which of the following can be oxidized by β-oxidation pathway? a. Saturated fatty acids b. Monosaturated fatty acids c. Polyunsaturated fatty acids d. All of these

96. Propionyl CoA is formed on oxidation of a. Monounsaturated fatty acids b. Polyunsaturated fatty acids c. Fatty acids with odd number of carbon atoms d. None of these

97. The glycosidic bond between sugar and base is broken by phosphate in both pyrimidine and purine catabolism. Why is this reaction not a problem during pyrimidine biosynthesis; that is, why doesn't the reverse of the reaction catalyzed by orotate phosphoribosyl transferase readily occur? a. Pyrophosphate is not reactive enough to break glycosidic bonds; only phosphate is. b. The phosphorolysis reaction can only occur with a nucleoside, not a nucleoside monophosphate. c. Orotate phosphoribosyl transferase produces pyrophosphate, and pyrophosphate is quickly degraded to phosphate. d. The carboxylate on orotate inhibits phosphorolysis.

98. Which of the following enzymes or enzyme combinations might allow an organism to avoid incorporating deoxyuridine into its genome? a. A nucleoside kinase that could phosphorylate any nucleoside to a nucleoside monophosphate. b. A nucleoside monophosphate kinase and a nucleoside diphosphate kinase that were specific for deoxyuridine nucleosides and nucleotides and did not use deoxythymidine nucleosides and nucleotides. c. A ribonucleotide reductase that was not allosterically regulated, allowing all nucleoside diphosphates to be reduced equally well. d. A nucleoside diphosphate kinase that did not use deoxyuridine nucleotides, and deoxyuridine diphosphate phosphatase

99. Mutants in adenosine deaminase cause T lymphocytes and B lymphocytes to develop improperly and lead to severe immune deficiencies. A plausible explanation for this is: a. Since adenosine is not broken down, RNA and DNA contain too much adenosine. b. Since adenosine is not broken down, too much ATP is produced and the cell's energy balance is thrown off. c. Since deoxyadenosine is not broken down, ribonucleotide reductase is down-regulated and too few deoxynucleotides are produced. d. Since deoxyadenosine is not broken down, purine biosynthesis and catabolism are stimulated, leading to the deposition of uric acid (similar to gout).

100. Glutamate dehydrogenase operates at an important intersection of carbon and nitrogen metabolism. An allosteric enzyme with six identical subunits, its activity is influenced by a complicated array of allosteric modulators. Mutation that alter the allosteric binding site that cause permanent activation of enzyme that lead to a human genetic disorder called hyperinsulinism-hyperammonemia is a. A mutation in negative modulator GTP. b. A mutation in positive regulator ADP c. A mutation in negative regulator GDP d. A mutation in positive regulator ATP