Biochem Reviewer 5

Biochem Exam 5 1. The leader sequence of preproinsulin a. Complexes with zinc b. Provides the conformation for the proper location of the disulfide bonds c. Directs the movement of the molecules through the cisternae of the ER d. An important portion of the C peptide 2. Mature insulin can be best escribed as a. Consisting of A and B chains separated by a C peptide b. 3 interchain disulfide bridges stabilize the molecule c. Disulfide bridges are contributed by methionine residues d. Composed of 51 amino acids, 21 in the alpha chain and 30 in the beta chain 3. Which is true about the insulin receptor a. It is a member of the G coupled receptor family b. Its alpha subunits contain the insulin binding sites c. The entire receptor is located in the cytoplasm of target cells d. The beta subunits phosphorylate critical tyrosine residues in the alpha subunits 4. Which is the proper sequence of events leading to insulin secretion? a. Glucose entry – phosphorylation – increase ATP/ADP – depolarization – calcium influx – insulin excretion b. Glucose entry increase ATP/ADP – phosphorylation – calcium influx – depolarization – insulin excretion c. Glucose entry – depolarization - phosphorylation – increase ATP/ADP – calcium – insulin excretion d. Glucose entry – phosphorylation – calcium influx – depolarization – increase ATP/ADP – insulin excretion 5. The effects of insulin on membrane transport of glucose include a. Enhanced glucose transport via GLUT in all tissues b. Translocation of GLUT from intracellular pool to the plasma membrane c. Inhibition of phosphorylation of glucose inside cells d. Stimulation of synthesis of GLUT in tissues 6. The effects of insulin deficiency on glucose utilization are a. Glycolysis is less than 50% b. 30-40% of glucose is converted to fats c. Glycogenesis is not affected initially d. All of the above 7. Gluconeogenesis is inhibited by insulin via inhibition of the transcription of a. Phosphoenol carboxykinase b. Pyruvate carboxylase c. Pyruvate dehydrogenase d. Pyruvate kinase 8. Insulin inhibits lipolysis by which mechanisms a. Decreased ATP b. Decreased cAMP c. Increased ATP d. Increased cGMP 9. Which best describes the glucagon receptor a. Its 2nd messenger is cAMP b. It is a g-protein coupled receptor c. Its binding to glucagon activates PKA

d. All of the above 10.Which of these GI hormones stimulates release of growth hormone a. Amylin b. Galanin c. Glucagon d. Ghrelin 11.Which of these gi hormones stimulates release of both insulin and catecholamines a. VIP b. PACAP c. Somatostatin d. Neurotensin 12.A dietary a. b. c. d.

deficiency of iodine would Directly affect the synthesis of the thyroglobulin on ribosomes Result in increased secretion of TSH Result in decreased production of TSH Result in increased heat production

13.One o the following statements about thyroglobulin is true a. It is the precursor of calcitonin b. It is iodinated, glycosylated carbohydrate c. It contains 115 tyrosine residues d. It is initially synthesized in the apical portion of the cell 14.The major stimulus for the thyroid to increase microvilli on the apical membrane is a. Iodine b. TSH c. NADPH d. Calcitonin 15.One of the following statements about iodine is true a. The average secretion of thyroid hormone iodide is 100 ug per day b. The average uptake of iodide is composed of 25-30% of the iodide ingested c. The daily iodide requirement Is 250-300 ug d. Most of the iodide in the thyroglobulin is in the form of iodothyronine 16.One of the following events is true of the concentration of iodide a. It is an energy dependent process and is linked to the atpase dependent Na K pump b. Thyroperoxidase is essential for the concentration of iodide c. It involves the iodination of the 3rd position of the aromatic ring d. Phagocytes and pinocytosis are essential in this process 17.One of the following statements about thyroid binding globulin is true a. Both t3 and t4 are equally bound to TBG b. Thyroxine binding prealbumin is quantitatively more important c. TBG bonds covalently nearly all the t3 and t4 d. Estrogens increase the synthesis of TBG 18.A 1 month old infant was noted to have prolonged jaundice at two weeks old. He usually has feeding difficulty and constipation. The temperature is usually subnormal and has mottled skin. No newborn screening test was done. The probable hormone level of this newborn is

a. b. c. d.

T3 high; TSH normal T4 low, TSH low T3 high, TSH High T4 low, TSH high

19.The mechanism of action of pertechnetate is a. It acts as an iodine transporter inhibitor b. It inhibits the TBG to attach to thyroid hormones c. It prevents coupling of MIT to DIT d. It inhibits hydrolysis of T3 20.One of the following enhances the transcription of the GH gene 1. T4 2. T3 3. TRH 4. TSH 21.The hormone responsible for the transport of calcium across the membrane that enclose sthe periosteal space is 1. TSH 2. PTH 3. 1, 23 dihydrocholecalciferol 4. Calcitonin 22.One of the following statements about calcium is true 1. There is approximately 5 kg of calcium in the human body 2. Hydroxyapatite crystals provide the inorganic component of the skeleton 3. Ionized calcium is the most common form of calcium 4. Calcium has a wide range of normality in all ages and sexes 23.The effect of alkalosis on serum calcium is 1. An increase 2. A decrease 3. No effect 24.A 1 ½ year old kid was noted to have an expanded wrist. On x-ray there us cupping and fraying if the hypertrophied metaphyseal plate. Review of history and physical examination revealed a stunted male patient with bow legged appearance of the leg. Laboratory examinations were requested and the typical findings of the patient will reveal 1. High 1-25, dihydrocheloecalciferol , high PTH 2. Low 1-25, dihydrocholecalciferol, low PTH 3. High 1-25, dihydrocholecalciferol, low PTH 4. Low 1-25, dihydrocholecalciferol,, high PTH 25.One of the following statements are true of 25 (OH) – D3 1. It is a weak agonist and modification by hydroxylation at position C3 results to full biologic activity 2. It is synthesized in the mitochondria of the renal proximal convoluted tubule 3. At least 2 enzymes are required for its conversion to its active metabolite 4. It is mediated by NADPH, Ca2+ and hydrogen peroxide 26.Low serum calcium will 1. Stimulate the release of PTH 2. Decrease the absorption of calcium in the intestine 3. Enhance the excretion of calcium in the urine 4. Increase the influx of calcium in the bone 27.One of the following statements about glucocorticoids is true except 1. Its synthesis requires 3 sequential hydroxylases 2. The most abundant and potent glucocorticoid in humans is corticosterone

3. Its main function is for the stimulation of gluconeogenesis 4. All glucocorticoids have mineralocorticoid activity 28.Aldosterone is exclusively synthesized in the glomerulosa because this particular enzyme is found on that region 1. 17 hydroxylase 2. 21 hydroxylase 3. 11 hydroxylase 4. 18 hydroxylase 29.All steroid hormones of the adrenal cortex come from this cholesterol product 1. Pregnenolone 2. Progesterone 3. 17-hydroxypregnenolone 4. 17-hydroxyprogesterone 30.This enzyme in glucocorticoid synthesis is located in the mitochondria 1. 17 hydroxylase 2. Β-OH steroid dehydrogenase 3. 21-hydroxylase 4. 11-hydroxylase 31.One of the following enzymes is not involved in the synthesis of androgens 1. 17 hydroxylase 2. 21 hydroxylase 3. 17-20 lyase 4. Β-OH steroid dehydrogenase 32.Which of the following statements is true about mineralocorticoids 1. There is no storage of the steroid hormone in the adrenal cortex 2. They are bound to a corticosteroid binding globulin in the plasma 3. They are excreted in the urine as glucoronide 4. During its synthesis hydroxylation starts at the 17th carbon atom 33.The potent stimulus for the synthesis of aldosterone is angiotensin II which is a 1. Decapeptide 2. Nonapeptide 3. Octapeptide 4. Heptapeptide 34.A deficiency of these enzymes except one will cause adrenal hyperplasia leading to overproduction of adrenal androgens 1. 21 hydroxylase 2. 17 hydroxylase 3. 18 hydroxylase 4. β-OH steroid dehydrogenase 35.an intermediate in catecholamine synthesis that crosses the blood brain barrier and is used in the treatment of parkinsons disease 1. dihydroxyphenylalanine 2. norepinephrine 3. dihydroxyphenylethanolamine 4. epinephrine 36.one of the following is a cofactor needed to convert tyrosine to L-DOPA 1. pyridoxal phosphate 2. tetrahydropteridin 3. vitamin c 4. tetrahydrobiopterin 37.release of catecholamines from the chromaffin granules to the ECF is stimulated by the following except 1. calcium 2. cholinergics 3. α-adrenergic agenst

4. β-adrenergic agents 38.one of the following statements is true about epinephrine 1. it is synthesized from norepinephrine by side chain hydroxylation 2. the enzyme responsible for the conversion is norepinephrine hydroxylase 3. it activates both alpha and beta adrenergic receptors 4. it iscatabolized by MAO and COMT to homovanilic acid 39.tyrosine is converted to L-DOPA by which reaction 1. ring hydroxylaytion 2. hydroxylation of the side chain 3. decarboxylation 4. methylation 40.the concentration of this metabolite is elevated in the urine on patients with tumor of the adrenal medulla 1. DOPA 2. Vanillylmandelic acid 3. Dopamine 4. Homovanillic acid 41.The following adrenergic receptor subgroups are coupled to the adenylyl system except 1. β-1 2. α-1 3. β-2 4. α-2 42.the following P450 group of enzymes is located in the endoplasmic reticulum except 1. P450 scc 2. P450 c17 3. P450 c21 4. P450 arom 43.Which of the following enzymes catalyze conversion of 17-hydroxyprogesterone to dehydroepiandrosterone 1. 17 a-hydroxylase 2. 17, 20 lyase 3. 17 ketoreductase 4. 17 β-isomerase 44.Mutation of this enzyme can lead to male pseudohermaphroditism 1. 17 20 lyase 2. 18 hydroxylase 3. 3 B hydroxysteroid dehydrogenase 4. 17 ketoreductase 45.The region or domain that confers specificity to a steroid hormone receptor 1. Ligand binding region 2. DNA binding region 3. Variable region 4. Zinc fingers binding region 46.Which steroid hormone receptor is located on the x-chromosome 1. Thyroid hormone receptor 2. Retinoic acid receptor 3. Estrogen receptor 4. Androgen receptor 47.Membrane receptors for oxytocin in uterine smooth muscle are increased by 1. Estrogen 2. Progesterone 3. Testosterone 4. Cortisol 48.This steroid hormone is the end product of the corpus luteum in the ovary 1. Estradiol

2. Testosterone 3. Dehydroepiandosterone 4. Progesterone 49.Predominant type of estrogen in non pregnant reproductive age women is 1. Estriol 2. Estradiol 3. Estrone 4. Estrin 50.This hormone is structurally related to proactin 1. Human placental lactogen 2. Human chorionic gonadotropin 3. Follicle stimulating hormone 4. Leutenizing hormone 51.Which hormone is responsible for the milk ejection or milk let doen reflex 1. Prolactin 2. Oxytocin 3. Estrogen 4. Progesterone 52.The checkpoint complex that regulates progeression from the growth phase to DNA synthesis 1. CDK1:D 2. CDK2:E 3. CDK6:D 4. CDK1:B 53.The processivity of DNA synthesis refers to the activity of 1. Dna ligase 2. Topoisomerase I 3. DNA polymerase 4. Helicase 54.Which statement best describes the function of the gene? 1. It encodes the primary sequence of a polypeptide 2. Regulatory sequences are located within the coding sequence 3. Te entire chromosome contains coding sequences 4. Its expression involves a complement of cytosolic enzymes 55.The structure of the dna molecule is described as 1. The backbone is stabilized by hydrogen bonds 2. The nitrogenous bases account for the polarity of the molecule 3. The antiparallel stands are complementary 4. The ribose component participates in base pairing 56.The themes that govern human dna replication includes 1. The information in the parent molecule is completely conserved in one new DNA 2. The antiparallel strands undergo simultaneous unwinding 3. The initial step involves the random nicking of an adenine-thymine rich sequence 4. All of the above 57.Which protein is not involved in the formation of the replication fork 1. Dam methylase 1 2. Dna polymerase 4 3. Rna polymerase 3 4. Dna gyrase 2 58.The subunit of the e. coli dna polymerase that attaches the enzyme to the template 1. α 2. β 3. δ 4. ε 59.the catalytic effect of dna gyrase during replication is to

1. increase the processivity of base pairing 2. stabilize the separation between the parent strands 3. relieve the topological stress in dna 4. attach a methyl group to break a phosphodiester bond 60.which activity initiates polymerization of a dna molecule during replication 1. attachment of an incoming dNTP to the RNA primer 2. cleavage of a phosphate from dNTP to provide energy of the reaction 3. phosphodiester bond formation between nitrogenous bases 4. separation of the template strands 61.in the mammalian cell, the synthesis of both the leasding and the lagging strand involves 1. reading of the template strand from the 3’ to the 5’ direction 2. attachment of the dNTP to the parent strand by a phosphodiester link 3. extension of the daughter strand by dna polymerase a 4. synthesis of a primer by dna polymerase a 62.the gap formed after primer removal is filled in by 1. rna polymerase 2. dna ligase 3. dna polymerase 4. rna hybridase 63.the activity og telomerases is best decribed as 1. the addition of nucleotide repeats involving adenine 2. requiring DNA as the template strand 3. are enzymes that produce dna molecules 4. incorporate nucleotides at the 3’-OH of the template 64.which mechanism will result in transversion 1. replacement of a cytidine with hymine 2. substitution of guanine with uracil 3. formation of dimmers 4. insertion of inosine 65.which reaction is required exclusively during base excision repair 1. gap filling 2. nucleotide sealing 3. nick sealing 4. sugar cleavage 66.homologous recombination involves the exchange of genetic information resulting in 1. movement of a sequence within the same dna molecule\ 2. exchange of segments between two dna molecules 3. jumping of genes within a chromosome 4. crossing over of sister chromatids (at holiday jxn) 67.the role of dna in rna synthesis can be characterized as 1. the nucleotide sequence for attachment of he promoter 2. forming a complementary base pair with the growing rna molecule 3. as the template read from the 5’ to 3’ direction 4. the attachment site for the TFIIB 68.which protein function pair is required during prokaryotic rna synthesis 1. TFIIB: ATPase activity 2. TFIIH: TBP binding 3. TFIIE: helicase activity 4. TFIIA: promoter recognition 69.Which sequence fo binding correctly indicates the formation of a preinitiation complex TFIID TFIIB TFIIA TFIIF TFIIE TFIIH 1. TFIID-TFIIE-TFIIF-TFIIB 2. TFIID-TFIIF-TFIIB-TFIIE 3. TFIID-TFIIB-TFIIF-TFIIE 4. TFIID-TFIIB-TFIIE-TFIIF

70.The function of the coding strand is to provide the 1. Nitrogenous base sequences to rna elongation 2. Signal for initiation called the promoter site 3. Attachment site for TFIIE and RNAPI 4. Indicator of the the termination of transcription 71.The core enzyme in RNA synthesis is fromed during 1. Template binding 2. Chain elongation 3. Chain initiation 4. Promoter clearance 72.The enzyme that attaches the acceptor arm of tRNA is 1. RNAse:P 2. tRNA:nucleotidyltransferase 3. exonuclease 4. rna polymerase 73.which statement describes the regulation of gene expression in mammalian cells 1. dna binding transactivator enhancer complexes inhibit transcription 2. coactivators act as intermediates between transactivators and RNAPII 3. specificity factors alter specificity of RNAP to the promoter site 4. repressors impede access of promoter site to RNAP modified multiple choice: write A if choice 1, 2, and 3 are correct



B if 1 and 3 are correct



C if 2 and 4 are correct



D if only 4 is correct



E of all are correct 74.steroid hormones formed from pregnenolone involve which of the following reactions 1. removal of the side chains at carbon 17 2. addition of double bonds at the A ring 3. hydroxylation series 4. oxidation with FMN and FADH2 75.which of the following steroid molecule:carbon number pairing are correct? 1. Progesterone: carbon 21 2. Testosterone: carbon 19 3. Androstenedione:carbon 19 4. Estradiol: carbon 18 76.The 3 β hydroxysteroid dehydrogenase/isomerase enymes participate in the following conversion reactions 1. Pregnenolone to progesterone 2. DHEA to androstenedione 3. Androstendiol to testosterone 4. Androstenedione to testosterone 77.Which of the following are true of the STAR protein 1. Acts as a cholesterol transport protein 2. Facilitates delivery of cholesterol to the inner mitochondrial membrane 3. Mutations in the STAR gene causes adrenal lipoid hyperplasia 4. Participates in the rate limiting step in steroidogenesis 78.Steroid not bound by sex hormone binding globulin include which of the following 1. Dihydrotestosterone 2. 17 a-testosterone 3. Estrone 4. Dehydroisoandrosterone 79.Conversion of pregnenolone to testosterone requires which of the following enzymes 1. 17 a-hydroxylase

2. 3 B-hydroxysteroid dehydrogenase 3. 17 B-hydroxysteroid dehydrogenase 4. Aromatase 80.Sex hormone binding globulin is decreased by which of the following 1. Estrogen 2. Androgen 3. Liver disease 4. Hypothyroidism 81.The following conversion reactions require P450arom (aromatase) enzyme 1. Androstendione to estrone 2. DHEA to androstenedione 3. Testosterone to estradiol 4. Estrone to estradiol 82.Ketosteroid metabolites of testosterone include which of the following 1. Pregnanediol 2. Androsterone 3. Dihydrotestosterone 4. Etiocholanolone 83.Dihydrotestosterone specific actions include 1. Spermatogenesis 2. Prostate development 3. Sexual differentiation into wolffian ducts 4. Sexual maturation at puberty 84.In the A cells of the pancreas, the products of preproglucagon include 1. Glucagon 2. GLP1 3. MPGF 4. Glicenin 85.Which of the following GI hormones inhibit secretion of insulin 1. GIP 2. CGRP 3. GLP-1 4. Galanin 86.Which of the following affect the amount of hormone within target cells 1. Dilution effect 2. Conversion to active form 3. Dissociation constant 4. Clearance rate 87.The following are features of group 1 hormones 1. Lipophilic 2. Receptors as proteins 3. Have long half life in circulation 4. Require intermediary molecules for activity 88.The proportion of bound and free hormones depends on the transport proteins 1. Rate of synthesis and secretion 2. Binding affinity 3. Solubility and polarity 4. Binding capacity 89.Hormone-receptor complex formation involves 1. Specificity\sensitivity to antagonist 2. Sensitivity to antagonist 3. Saturation 4. Bioavailabiliy 90.Which enzyme;reaction pair is observed during post translational modification of mRNA 1. Methyltransferase; 3’-5’ attachment of guanine

2. Poly-A polymerase; attachment of 5’ end of mRNA to adenine 3. Ribinuclease; cleavage of oligonucleotide at the 5’ end of mRNA 4. snRNP; attachment of 5’-3’ end of exons 91.the precursors of dna-dapendent rna polymerase include 1. uriidine triphosphate 2. adenosine triphosphate 3. cytidine triphosphate 4. guanosine monophosphate 92.which reactions are observed in both DNA and RNA synthesis 1. elongation through nucleophilic attack of the 5’ end of the incoming nucleotide 2. base pairing between the template strand and the daughter strand 3. unwinding of the dna helix to form a bubble 4. synthesis of an rna molecule for initiation to start 93.posttranscriptional modification of rRNA produces 1. 5.8S 2. 18S 3. 28S 4. 41S 94.Conditions that allow for the synthesis of DNA from RNA includes 1. Dna dependent rna polymerase 2. 5’ to 3’ polarity 3. cDNA as a template 4. tRNA as a primer 95.Molecular signals decreases the expression of the following genes 1. Housekeeping 2. Inducible 3. Constitutive 4. Repressible 96.Polymerization of DNA and RNA requires 1. Nucleophilic attack on the 5’ OH of the incoming nucleotide 2. Hydrolysis of ATP to Pi 3. Hydrogen bond formation between template and growing chain 4. Synthesis of RNA primer for elongation 97.The genes in the lac operon code for the following enzymes 1. B-galactosidase 2. Galactoside permease 3. Thiogalactoside transacetylase 4. B-allolactase For numbers 98-102, the statements pertain to cAMP as a second messenger Write A if the statement is true, B if it is false 98.Involves serpentine signaling mechanism 99.It uses ionic channels (Ca2+) as part of the intracellular signaling mechanism 100.It influences the manner the intracellular ligand interacts with the cytoskeleton 101.Its synthesis requires association with a-subunit of G protein 102.It binds to the regulatory subunit of PKC Matching type: match the hormone in column A to its 2nd messenger in column B. you may use the options more than once Column A 103.Prolactin 104.Erythropoietin 105.Lipotropin

Column B A. cAMP B. kinase/phosphate cascade C. Ca2+/PIP2 D. cGMP E. NO LABORATORY 106.In blood glucose determination using Horizon procedure a. d-gluconic acid is measured at 405nm b. at 405nm, the color intensity correlates well with blod glucose levels c. quinonenimine formation is stabilized by addition of of hydrogen peroxide d. p-hydroxybenzene sulfate enhances the formation of a stable red dye 107.this is the best indicator of basal metabolic rate a. random blood sugar b. oral glucose tolerance test c. fasting blood sugar d. glycohemoglobin test 108.measures of fuel metabolism in the body includes a. lipid profile b. FBS c. BMI d. All of the above 109.The variable stability of specimen for blood glucose determination is due to a. Rbc lysis in the stiored specimens b. Bacteria contamination of specimens c. Glycolytic activity in RBC d. All of the above 110.Eliminating the influence of physical activity and diet, this blood determination indicates fuel source status a. Serum lipid profile b. BMI c. FBS d. All of the above 111.This is true of glycohemoglobin a. It is a measure of an average blood glucose levels in 2-3 months duration b. Glucose attaches to the NH3 terminus of the 4 globin chains c. Its levels correlate well with life expectancy in DM type 2 patients d. All of te above 112.Impaired glucose tolerance correlates with a. FBS = 70-110mg/dL b. 2o OGTT = 140-< 200 mg/dL c. RBS = 110-125 mg/dL d. B and C only 113.To document an increase of blood glucose after a meal by a physiologic means, this/ these tests are requested a. RBS b. Pos prandial BS c. OGTT d. B and C only 114.The following is true of gestational DM a. The most reliable screening test is OGTT b. GDM is established if blood glucose levels are elevated at 2 hours post glucose intake

c. Only pregnant women with family history of DM should be screened for the condition at 24-28 weeks d. A and B only 115.GDM occurs because of a defect in a. Insulin action b. Insulin receptor substrate -1 (IRS-1) expression c. Tyrosine kinase activity d. A and B only

Answers 1. C 2. D 3. B 4. A 5. B 6. A 7. A 8. B 9. D 10.B 11.B 12.B 13.C 14.D

15.B 16.A 17.D 18.D 19.A 20.B 21.B 22.B 23.B 24.D 25.B 26.A 27.B 28.D 29.A

30.D 31.B 32.B 33.C 34.C 35.A 36.B 37.C 38.C 39.A 40.B 41.D 42.A 43.B 44.D

45.C 46.D 47.A 48.B 49.D 50.A 51.B 52.C 53.C 54.A 55.C 56.B 57.B 58.C 59.C 60.A 61.A 62.C 63.C 64.B 65.D 66.D 67.B 68.D 69.C 70.B 71.C 72.B 73.B 74.B 75.E 76.A 77.E 78.B 79.A 80.C 81.B 82.C 83.C 84.B 85.C 86.E 87.A 88.C 89.A 90.D 91.A 92.E 93.A 94.C 95.D 96.B 97.A 98.A 99.B

100.D 101.A 102.B 103.B 104.B 105.A 106.D 107.C 108.D 109.B 110.D 111.D 112.B 113.D 114.B 115.B