Biochem final exam - 2020 PDF

Preview

Summary

Download Biochem final exam - 2020 PDF

Description

1. Which one of the following redox-systems is with highest redox potential? - Ferric cytochrome a/ ferrous cytochrome a 34)

A. E, D, C, B, A 32) All of the following are electron carriers in the electron transport chain EXCEPT: D. Hemoglobin 35) In the mitochondrial respiratory chain the electrons flow from ubiquinone to oxygen through the redox couples of cytochromes. The correct sequence of the cytochrome (...) a spontaneous electron flow is: B. b-c1-c-a-a3 38) Energy generated from metabolic fuels is used for: B. muscle contraction 36) Mark the correct answer. The transmembrane proton gradient: D. provides energy for the synthesis of ATP from ADP+Pi

3) Which of the following cofactors is required for the synthesis of gamma-amino butyric acid (GABA) , serotonin, epinephrine, dopamine and histamine from the respective aminoacid precursors? A. tetrahydrobiopterin

1)Which one of the following enzymes is a pancreatic one involved in proteins digestion? B.trypsin 6) The enzyme enteropeptidase plays an important role in the proteins digestion because it converts: B. Trypsinogen into trypsin 4) Which are the tissues involved in glucose-alanine cycle? C. Liver and muscles 2) Which one is correct? - Urea cycle occurs in cytosol and endoplasmic reticulum of hepatocytes - Urea cycle is endergonic process - Ornithine transcarbamoylase is cyto - N-acetylglutamate is an allosteric inhibitor of carbamoyl phosphate synthease I 9) Which of the following compounds is an intermediate in the conversion of ketone bodies to acetylCoA? D.Acetoacetyl-CoA 10) Which is the rate limiting step in cellular cholesterol biosynthesis? A. HMG CoA reductase 7) A physiological methylating agent is: -Choline -N5-methyl-tetrahydrofolate 8) Which of the following enzymes is responsible for degradation of plasma triglycerides in VLDL to free fatty acids and glycerol? D. Lipoprotein lipase 5) Which of the following is NOT required for amino acid absorption from the intestinal lumen into the intestinal epithelial cell? C. Glucose 33) Coenzyme Q is a component of the mitochondrial electron transport chain. It: D. Is a lipid-soluble electron carrier 30) Which of the following micronutrients ARE NOT micronutrients? A. phytonutrients

31) Which of the following aminoacids is essential and has to be supplied by the human diet? C. Methionine 24) Which of the following is NOT one of the active forms of the folic acid in human body? D. Dihydrofolate 29) Which of the following fatty acids DOES NOT become an essential , when both linoleic and alpha-linolenic acids are deficient? B.Eicosapentaenoic acid 23) Cofactor of the enzyme involved in synthesis of deoxyribonucleotides is: C.thioredoxin 43)Correct combination with characteristics of conjugated bilirubin: -direct, hydrophilic, bilirubin diglucuronide 44)conversion of a zymogen: A. Limited proteolysis 45). Choose the incorrect statement concerning the cytP450 enzymes superfamily: -involved in reactions of specific and non-specific hydroxylation 46). Which of the statement conderning iron metabolism is FALSE: Hepcidin regulates the absorption of iron in the liver 47)Choose the incorrect statement for delta-aminolevulinic acid: - Can be induced by phenobarbital and some steroids 48)Deltaaminolevulinic acid (ALA) synthase activity: -Catalyses the rate-limiting reaction in porphyrin biosynthesis 51. In the biosynthesis of 1,25 dihydroxycholecalcifer ol from 7- dehydrocholesterol: C. Is required ultraviolet light

52. Mark the correct statement. A signaling cascade induced by adrenaline: All statements are correct

53. Deoxynucleotide synthesis requires:

Tetrahydrofolate + ribonucleotide reductase

54. Which of the listed below is the rate limiting enzyme in gluconeogenesis: Fructose 1,6 biphosphotase 55. Which of the following is not a stage in the proteoglycans synthesis? Transfer of branched oligosaccharide to asparagine residue with participation of dollichol

56. How many molecules of ATP are synthetized if one molecule of glucose is degraded into pyruvate and the obtained NADH+H+ is transferred to the mitochondria via the malate-aspartate shuttle? A. B. C. D.

4 6 8 12

57. Which statement for pentose phosphate pathway is INCORRECT: A. The main source of NADPH in the body B. Provides cells with ATP C. Takes place in the cytosol D. Shares common metabolites with glycolysis 59. The transport of glucose across the cell membrane is stimulated by insulin in : A. Liver B. Red blood cells C. Skeletal muscle D. Brain 60. Transporter Glut- 4 A. Is activated by insulin B. Facilitates glucose transport in the brain C. Is the prymery glucose transporter in the brain D. Transports glucose out of the cell 61. Patients with glucose-6- phosphate deficiency : A. Can use only muscle glycogen to maintain blood glucose levels B. Can convert both alanine and glycerol to glucose to maintain blood glucose levels C. Can use only liver glycogen to maintain blood glucose levels

D. Cannot maintain blood glucose levels either by glycogenolysis or by gluconeogenesis 62. All of the following are responses to increased NADH / NAD+ ratio, EXCEPT: A. Decreased rate of glycolysis B. Activated conversion of pyruvate to acetyl CoA C. Increased rate of electron transport D. Decreased rate of the TCA cycle

63. Which of the following compounds is NOT a component of the polyol pathway for glucose metabolism? A. Manitol B. Aldose reductase C. Sorbitol D. Fructose 64. Delta - aminolevulinic acid(ALA) dehydratase: C. Present in cytosol + D. inhibited by lead 65. Decrease production of prostaglandins in observed under nutritional deficiency of: A. Linolenic acid 66. A person with obesity and non - insulin dependent diabetes usually shows: C. Improved glucose tolerance after decreasing the body weight 67. Which of the listed amino acids is essential for healthy humans? B. Valine 68. Glucagon action results in activation of which of the following enzymes? A. Glycogen debranching enzyme (4:4 transferase) 69. Metabolic consequence of diet enriched of protein is: B. Increased production of urea 70. Which of the following enzymes contain pyridoxalphosphate as a prosthetic group? B.aspartat aminotransferase 71.What is the correct statement about hemoglobin in adults (HbA1)? C. Consist of two alpha and two beta polypeptide chains

72.Under which of the following conditions the affinity of hemoglobin to oxygen will be increased: D.one or more hemes saturated with oxygen 73.Which one of the following statements is INCORRECT: B.Amino acids have maximal buffer capacity at their isoelectric points (pI) 74.Which one of the following is NOT a characteristic of a tRNA molecule? A.Beta arm 75.Codons that code for the same amino acid are called: B.Synonyms 76. Which of the following statements is incorrect? A. allopurinol is a competitive inhibitor of the enzyme xanthine oxidase B. forming of sodium urate crystals is a result of chronic hyperuricemia C. hypoxanthine has lower solubility than uric acid D. hypoxanthine guanine phosphoribosyltransferase deficiency is the cause for nyhan syndrome

lesch-

77. Which of the following cofactors is directly necessary for ribonucleotide reductase activity? A. ATP B. NADH C. thioredoxin D. Vitamin b12 78. Which of the following statements about de novo biosynthesis of punne nucleotides is FALSE? A. N3 is supplied from aspartate B. Glycine is embedded at 4, 5 and 7 position in the purine ring C. C2 and C8 are supplied from formyl-tetrahydrofolate D. CO2 is a source for C6 79. Salvage reactions make nucleotides dependent on the availability of: A. Glutamine B. CO2 C. Allopurinolen D. phosphoribosyl pyrophosphate 80. A short-term effect of insulin is to depress triglyceride mobilization by: A. inhibiting hormone sensitive lipase

B. restricting blood flow to adipose tissue C. inhibiting glucose uptake by the cells D. stimulating protein synthesis 81. In which of the following are the enzymes are in correct metabolic sequence? A. Beta-hydroxyacyl dehydrogenase, enoyl hydratase, acyl dehydrogenase, thiolase B. Acyl dehydrogenase, beta-hydroxyacyl dehydrogenase, enoyl hydratase, thiolase C. Acyl dehydrogenase, enoyl hydratase, beta-hydroxyacyl dehydrogenase, thiolase D. Enoyl hydratase, thiolase, beta-hydroxyacyl dehydrogenase, acyl dehydrogenase

82. Which of the statements below describes nonfunctional plasma enzymes: A. Their substrate are always present in the blood B. They are not used as diagnostic markers C. Normally they function in the cells and can be found in the blood plasma in very low concentrations D. They are not active under physiological conditions 83. Mark the CORRECT answer The signal transduction mechanism of growth factors involves: A. Trimeric G-protein B. Only dimerization of the receptor protein C. Only autophosphorylation of the receptor protein D. Monomeric G-protein 84. Mark the CORRECT answer Binding ligands to many G-protein linked receptors lead to: A. A decrease in the concentration of certain intracellular signalling molecules called secondary messengers B. An increase in the concentration of certain intracellular signalling molecules called secondary messengers C. An increase in the concentration of certain extracellular signalling molecules called first messengers D. A decrease in the concentration of certain extracellular signalling molecules called first messengers 85. Which of the following is NOT correct? (the picture was hard to read)

The activation of different G-proteins results in A. Activation of phospholipase C, when G-alpha is active B. Increased production of phospha... ….when G-alpha is active C. InactivecGMP phos….. When G-aT is active D. Increased production of cAMP, when G-alpha is active 86. Which of the following statements about enzymes is INCORRECT: A. All enzymes work with maximal velocity at neutral pH (pH optimum = 7.4) B. One enzyme can interact with one or few substrates C. Each enzyme can catalize only one type of chemical reaction D. The velocity of an enzyme reaction can be defined as the number of the substrate molecules converted to product per unit time

87. Mark the CORRECT answer The receptors are characterized with: A. High affinity to the signal molecule and low binding specificity B. Low affinity to the signal molecule and high binding specificity C. Low affinity to the signal molecule and low binding specificity D. High affinity to the signal molecule and high binding specificity 88. Which of the following is NOT a feature of enzymes that distinguishes them from inorganic catalyst? A. High substrate and reaction specificity B. protein nature C. Enzyme activity can be regulated, so that rate of product formation responds to the needs of the cell D. Stability at high temperature 89. Michaelis constant, Km: A. Is numerically equal to the substrate concentration at which the velocity of the reaction is half the maximal B. Depends on enzyme concentration C. Is numerically equal to Vmax/2 D. Does not depends on pH 90. Which of the following statements is NOT correct for isoenzymes: A. Most commonly they are proteins with quaternary structure

B. May differ in their Km values C. They can have different regulation (they can have different activators/inhibitors) D. They have the same primary structure 91. At what pH amino acid exhibit minimal buffering properties? A. pH values equal to pK of COOH and NH2 groups B. pH values equal only to pK of COOH group C. pH values equal only to pK of NH2 group D. At the isoelectric point 92. What group amino acids (according to the properties of their side chains) contain R groups that can form hydrogen bonds with water? A. Basic amino acids B. Acidic amino acids C. Polar, uncharged amino acids D. Nonpolar amino acids

93. Which combination includes only basic amino acids? A. Lysine, arginine, histidine B. Lysine, cysteine, histidine C. Glycine, alanine, proline D. Tyrosine, arginine, histidine 94. Which of the following amino acids does not contain aromatic ring? A. Phenylalanine B. Tryptophan C. Serine D. Tyrosine 95. Which of the following amino acids is polar? A. Valine B. Aspartate C. Leucine D. Isoleucine 96. Choose the correct statement for the fetal hemoglobin (Hb F) A. HbF is obtained as a result of conservative substitution of amino acids B. HbF is composed of two a and two b chains\ C. Hbf has higher affinity for 2,3-BPG

D. Hbf has a higher affinity for oxygen than does HbA 97. Which of the following statements is NOT correct for allosteric enzymes? A. The graph, that describes the dependence of the reaction rate on the concentration of the substrate….. B. There is a cooperative effect of interaction between subunits C. Most often these are proteins with quaternary structure D. Most often regulatory enzymes are allosteric enzymes 98. Which of the following statements describe the Noncompetitive inhibition: A. The inhibitor is a structural analog of the substrate B. The rate of inhibition depends on the substrate and inhibitors concentration C. The rate of inhibition depends on the inhibitor concentration only D. The inhibitor binds to the active site 99. Mark the correct statements about elastin: A. The denaturation of elastin is reversible B. Desmosine linkage is formed in elastin C. Elastin has regularly spaced alanine residues D. Elastin is degraded by dipeptidylpeptidase 100. What is the name of the disease caused by a point mutation in the beta-globin chain characterized with replacement of glutamate with valine? A. HbC disease B. Methemoglobinemia C. Sickle cell anemia D. Beta-thalesemia 101. What enzyme profile is characteristic for heart disease? AST, CPK, LDH-1 102. Essential amino acids? Phenylalanine Valine Threonine Tryptophan Isoleucine Methionine Histidine Arginine Leucine

Lysine 103. non polar amino acids? glycine alanine valine leucine methionine isoleucine Proline 104. polar uncharged amino acids? serine, threonine, cysteine, asparagine, glutamine 105. polar charged amino acids (basic) lysine, arginine, histidine 106. polar charged AA (acidic)? aspartic acid, glutamic acid 107. AA with aromatic rings: Phenylalanine, Tyrosine, Tryptophan 108. Which statement concerning hemoglobin and myoglobin is true? a. They are localized in different parts of the body 109. Which of the following molecules is composed of 2 alpha chains and 2 gamma chians? a. Fetal hemoglobin 110. What is the shape of myoglobin dissociation curve? a. Hyperbolic (hemoglobin is sigmoidal) 111. What is the shape of hemoglobin dissociation curve? a. Sigmoidal 112. Which statements about HbF is correct? a. Due to an amino acid change in the binding site for 2,3 bisphosphoglycerate, HbF has lower affinity to 2,3-bisphosphoglycerate 113. Under what circumstances is formed the Barts hemoglobin? a. alpha -thalassemia

114. Which of the following statements is correct? a. Hydrogen bonds in tertiary structure of proteins are formed between amino acids from different polypeptide chains b. Primary structure of proteins is formed by non-covalent bonds c. No one is correct d. Hydrogen bonds in tertiary structure of proteins are formed between amino acids located far away from each other on the same polypeptide chain 115. Mark the correct combination regarding the physiological allosteric effectors of hemoglobin: a. CO2, H+, 2,3-bisphosphoglycerate b. CO2, H+, 2,3-bisphosphoglycerate, heme-heme interaction c. CO, H+, 2,3-bisphosphoglycerate, heme-heme interaction d. CO2, CN, CO 116. Which of the following has highest affinity for oxygen? a. Myoglobin 117.Which one is the biologically active form of vitamin B3? a. Nicotinamide adenine dinucleotide (NAD)

118. Which one is the biologically active form of vitamin B2? a. Flavin adenine dinucleotide (FAD) 119. non essential vitamin which can be synthesized of cholesterol? A. Vitamin D 120. Asians lack ______ dehydrogenase which can contribute to a flushing, headaches, and nausea. A. mitochondrial acetaldehyde dehydrogenase 121. degradation of ethanol in the body to at first: acetaldehyde, then acetic acid by 2 enzymes a. alcohol dehydrogenase, acetaldehyde dehydrogenase 122. Van der Waals forces act in: A. Myoglobin

123 . Where do the triacylglycerol of chylomicrons originate? A . they are taken up the intestinal lumen B . they are newly synthesized by intestinal cells C . they are synthesized by hepatocytes D . they are synthesized by adipocytes

124. Which of the following statements concerning bile salts is TRUE? A . they are derived from the cholesterol in all tissues of the body B . they can contain alanine or serine residues C . they are secreted in the bile and reabsorbed in the intestine D . they contain lonic groups with a positive charge

125. a person with a famial hyperlipidemia caused by a deficiency of LDL receptors was treated with an 3-hydroxy-3 methylglutaryl-CoA (HMGCoA) reductase inhibitor. The drug would cause A . blood cholesterol levels to decrease B . cellular levels of HMGCoA to decrease C . cellular levels of squalene to increase D . blood triacylglycerol levels to increase

126. the concentration of plasma cholesterol can be increased by which of the following interventions? A . inhibition of the enzyme 3-hydroxy-3methyl-glutaryl-CoA (HMG CoA) reductase B . increased production of bile acids by the liver C . ingestion of bile acid – binding resins

D . reduction in the number of LDL receptors on cell membranes

127 . what compound can always be found within a ganglioside? A . phosphatidylinositol B . choline C . phosphate D . sialic acid

128 which of the following enzymes is involved in the conversion of progesterone to testosterone? A . 5a-reductase B . 17.20=lyase C . 11 ß-hydroxylase D . aromatase

PRACTICALS Explain how ribose-5gphosphate is used for the Synthesis of nucleotides if glucose 6-p is deficient? Diminished G6PD activity impairs the ability of the cell to form the NADPH that is essential for the maintenance of the G-SH pool. This results in a decrease in the detoxification of free radicals and peroxides formed within the cell SH also helps maintain the reduced states of sulfhydryl

groups in proteins, including hemoglobin. Oxidation of those sulfhydryl groups leads to the formation of denatured proteins that form insoluble masses (called Heinz bodies) that attach to RBC membranes. Although G6PD deficiency occurs in all cells of the affected individual, it is most severe in RBC, where the pentose phosphate pathway provides the only means of generating NADPH. Additionally, the RBC has no nucleus or ribosomes and cannot renew its supply of the enzyme. Thus, RBC are particularly vulnerable to enzyme variants with diminished stability.

What is scurvy ? Describe the biochemical mechanism of scurvy. (or something like that): Vitamin C deficiency is called Scurvy, u can have different symptoms like alteration of the extracellular matrix in bones, skin, tendons.. These are caused by inactivation of some ascorbic dependent enzymes. It's not a genetic disease, it happens because of deficiency in ascorbic acidnd prolys hydroxylase, which causes impaired synthesis and cross linking of collagen fiber which then causes a decreased tensile strength of the collagen fibre. Many of the deficiency symptoms can be explained by the decreased hydroxylation of collagen, resulting in defective connective tissue. A microcytic anemia caused by decreased absorption of iron may also be seen

Main steps in synthesis of calcitriol. What is the biological role of calcitriol: Main steps involve, 7dehydrocholestrol present in skin then with action of UV radiation it synthesizes to cholecalciferol(D3) then with the help of enzymes in the liver(25hydroxylase) synthesizes to 25OHcalciferol then with presence of kidney enzymes and parathyroid hormone it synthesises to inactive and active (calcitriol) While it roles is to increases the intestinal ca2+ and phosphate absorption and stimulates release of them from the bone, as well as help in transport of ca2+ from intestinal lumen to blood, and it decreases the kidney se...