Block 2

Exam Section 2: Item 1 of 50 National Board of Medical Examiners Time Remaining:■ Mark Comprehensive Basic Science Self-Assessment 3 hr 59 min 21 sec

1. A 54-year-old woman has chronic symmetric swelling and tenderness in her proximal interphalangeal and metacarpophalangeal joints. She has muscle aches and stiffness, especially on awakening. Analysis of serum shows antibodies able to bind human IgG. These antibodies are most likely to recognize which of the following pairs of labeled domains in the schematic diagram of an IgG molecule?

© A) 1 and 2© B) 1 and 5© C) 2 and 3© D) 2 and 6© E) 3 and 4© F) 5 and 6

Exam Section 2: Item 2 of 50■ Mark

National Board of Medical ExaminersComprehensive Basic Science Self-Assessment

Time Remaining:3 hr 58 min 56 sec

2 A 17-month-old boy has a history of recurrent bacterial infections. Neutrophils stimulated with opsonized bacteria show decreased production of 0 2_, H20 2, HOCI, and *OH. Which of the following enzymes is most likely deficient in this patient?

© A) Catalase © B) Glutathione peroxidase © C) Myeloperoxidase © D) NADPH oxidase © E) Superoxide dismutase

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3. Tay-Sachs disease is an autosomal recessive disorder for which the carrier frequency in individuals of Ashkenazi Jewish descent is about 1 in 30. On the basis of this carrier frequency, which of the following is the best estimate of the probability that a child born to two parents, both of whom are of Ashkenazi Jewish descent, will be affected by Tay-Sachs disease?

© A) 1 in 15© B) 1 in 60© C) 1 in 450© D) 1 in 900© E) 1 in 1800© F) 1 in 3600

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4. During bacteriophage T7 infection of a single Escherichia coli cell, 1000 bacteriophage particles are released. One of these particles contains a fragment of the E. coli chromosome rather than the T7 chromosome. Will this phage be able to inject its DNA into an E. coli cell, and, if so, how many T7 particles will be produced by this cell?

Able to Inject DNA? # of T7 Particles ProducedA) Yes 1000B) Yes 100C) Yes 1D) Yes 0E) No 0





5. An 11 -year-old boy has been passing large volumes of urine and has been extremely thirsty over the past 10 days. He has lost a considerable amount of weight despite having a good appetite. During the past 2 days, he has become increasingly drowsy, lethargic, and difficult to arouse. Respirations are deep and rapid. His blood pressure is 100/60 mm Hg while supine and 40 mm Hg/undetectable while sitting. In addition to glucose, which of the following is the principal fuel oxidized in his brain?

© A) Alanine© B) Glutamate© C) Glycogen© D) P-Hydroxybutyric acid© E) Palmitate© F) Triacylglycerol

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6. A biosynthetic error in reading the genetic code gives rise to an enzyme that folds in an abnormal manner. Which of the following is most likely to happen to this enzyme?

® A) Denaturation and refolding © B) Faster degradation © C) Inactivation by phosphorylation © D) Transportation out of the cell via the Golgi complex





7. A 61-year-old woman has had progressively severe pain in the right ear over the past 24 hours. She has had type 1 diabetes mellitus for many years and has mild renal failure, retinopathy, and neuropathy. She has no history of drainage from the ear, upper respiratory tract infection, fever, or chills. She is afebrile. Hearing is normal bilaterally. The external appearance of the ear is normal, but touching or moving the pinna produces severe pain. The external auditory canal is inflamed. The tympanic membrane is clear, and no fluid is seen. Which of the following is the most likely diagnosis?

© A ) Acoustic schwannoma © B) Acute otitis media © C) Labyrinthitis © D) Malignant otitis externa © E) Polychondritis

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8. A geneticist has artificially produced a microorganism that contains a new combination of genes. He wants to know if recombination or transposition has occurred. The major difference between these two processes is that recombination involves which of the following?

© A ) DNArepair© B) Endonuclease sites© C) Gene rearrangement© D) Homologous sites© E) Sites on the same chromosome

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9. A 40-year-old woman has a 3-month history of shortness of breath, chest pain, fever, and night sweats. An x-ray of the chest shows lymph node enlargement. Tissue obtained on a lymph node biopsy is shown. These findings are most consistent with which of the following types of inflammation?

© A ) Fibrinous © B) Granulomatous © C) Necrotizing © D) Serous © E) Suppurative

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10. A 74-year-old woman is brought to the physician by family members who are concerned because she has been losing weight. She has a history of chronic anxiety and dysthymic disorder. An x-ray of the chest shows a large central mass. Unresectable lung cancer is diagnosed. The woman is capable of informed decision-making, but her family asks that she not be told the diagnosis because they feel the news will hasten her death. Which of the following is the most appropriate response?

© A) Tell the family it is uncomfortable continuing as her physician under these circumstances and suggest alternative physicians they might consult © B) Tell the patient about the x-ray findings, refer her to an oncologist, and consult with a risk management attorney © C) Tell the patient that her test results are available for discussion if she wishes© D) Tell the patient that she should be referred to an oncologist for a second opinion and inform the oncologist about the dilemma © E) Tell the patient that the x-ray is abnormal and that she should see a specialist

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11. Which of the following laboratory tests is most useful in differentiating Streptococcus pneumoniae from other a-hemolytic streptococci?

© A) Bacitracin (A disk) susceptibility © B) Catalasetest © C) Coagulase test © D) Lactose fermentation © E) Optochin (P disk) susceptibility © F) Oxidase production © G) Urease production





12. When adipocyte triglycerides are mobilized, the nonfatty acid domain of this molecule can be used by the liver for gluconeogenesis. Which of the following enzymes initiates this process?

© A) 1,3-Diglycerate kinase© B) Fructose 1,6-bisphosphatase© C) Glucokinase© D) Glyceraldehyde-3-phosphate dehydrogenase© E) Glycerol kinase© F) Hexokinase

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13. Dry heat at 100°C for 60 minutes is used to sterilize instruments at a small community outpatient facility. Using this technique, which of the following is most likely to survive as a viable contaminant of the sterilized instruments?

© A) Bacillus subtilis © B) Escherichia coli © C) Pseudomonas aeruginosa © D) Staphylococcus aureus © E) Streptococcus pyogenes (group A)





14. Which of the following structures are most likely found with the structures labeled T in the photomicrograph?

© A) Adhesion plaques © B) Gap junctions © C) Hemidesmosomes © D) Myosin filaments © E) Tight junctions (zonulae occludentes)

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15. A 55-year-old Native American woman who lives alone is brought to the emergency department after a minor fall in her home, which her mother witnessed. She tells her physician that her husband, who died 6 weeks ago, comes to visit her every night and gives her guidance. She also states that he complains of being lonely and is waiting for her to join him. She states that her appetite and energy are normal and denies suicidal ideation. Physical examination shows a bruised arm and leg. Neurologic examination and CT scan of the head show no abnormalities. Which of the following is the most appropriate next step for the physician?

© A) Ask her relatives if speaking to deceased loved ones is common to their culture © B) Ask her relatives if there is a family history of major depressive disorder with psychotic symptoms © C) Ask her relatives if there is a family history of schizophrenia © D) Order an EEG to determine if the patient is sleep-deprived © E) Order an MRI of the head





16. A 48-year-old man has a painless enlarged axillary lymph node. Excisional biopsy shows replacement of nodal architecture by neoplastic follicles composed of small cleaved lymphocytes. Cytogenetic studies show a t(14;18). Alteration of which of the following processes most consistently underlies the pathogenesis of this lesion?

© A ) DNArepair © B) Growth factor production © C) Growth factor receptor regulation © D) Nuclear transcription factor expression © E) Regulation of apoptosis

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17. A 69-year-old woman is brought to the emergency department 1 hour after the sudden onset of crushing, substernal chest pain and nausea. Physical examination shows pallor and diaphoresis. An ECG and an evaluation of serum cardiac enzyme activity confirm a diagnosis of a myocardial infarction of the anterior wall. Activation of platelets and segmented neutrophils during thrombogenesis in this patient caused the release of cytokines, including platelet-derived growth factor. The mitogenic signal provided by this cytokine to smooth muscle cells at sites of vascular injury in this patient is most likely to be inhibited by which of the following intracellular enzymes?

© A) Aminotransferase© B) Glycosylhydrolase© C) Kinase© D) Lipase© E) Peroxidase© F) Phosphatase

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18. A 23-year-old woman (individual 11-1 in the pedigree) seeks genetic counseling because her brother has Duchenne muscular dystrophy (DMD). Her brother (II-2) has a deletion in the DMD gene. Although her mother (I-2) does not have the deletion, individual 11-1 is told that her risk for carrying the DMD gene is greater than that of the general population. Which of the following best explains this increased risk?

© A) De novo gene mutation © B) Locus heterogeneity for DMD © C) Maternal germline mosaicism © D) Promoter mutation © E) Suspected parental consanguinity © F) X inactivation





19. A 55-year-old woman is treated with 500 mg of drug X three times daily for cancer pain. She is pain-free, but she develops nausea, vomiting, and diarrhea, requiring cessation of drug X. Drug Y is started at 20 mg twice daily. She is pain-free, her appetite improves, and she gains weight. Which of the following best describes the maximal efficacy of these drugs?

© A) Drug X is more efficacious than drug Y © B) Drug Y is more efficacious than drug X © C) Drugs X and Y are equally efficacious





20. Treatment of human lymphoid tissue with an experimental drug that causes overexpression of the bcl2 protein is most likely to result in a decrease in which of the following in B lymphocytes?

© A) Apoptosis© B) FAS protein© C) Intracellular adhesion molecule-1© D) NADPH oxidase© E) Uric acid



National Board of MedicComprehensive Basic Scienc

21. Sequence-specific cleavage of proteins plays a role in which of the following processes?

® A) Activation of G proteins by hormone receptors © B) Assembly of microtubules © C) Cellular uptake of iron © D) Initiation of coagulation © E) Transport of proteins into the nucleus

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22. A 1-month-old boy with hydrocephalus has suspected Toxoplasma gondii infection. Which of the following routes of infection is most likely in this patient?

© A) Arthropod bite © B) Exposure during vaginal delivery © C) Ingestion of cow's milk © D) Ingestion of mother's milk© E) Postnatal transmission from an infected family member © F) Postnatal transmission from a family pet © G) Transplacental transmission

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23. Which of the following molecules must interact to induce immune cell activation by the superantigen toxic shock syndrome toxin-1?

Molecule 1 Molecule 2® A) Class I MHC complement receptor 1© B) Class I MHC IgM, IgD© C) Class I MHC T-cell receptor© D) Class II MHC complement receptor 1© E) Class II MHC IgM, IgD© F) Class II MHC T-cell receptor

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24. The splicing of primary gene transcripts in eukaryotic cells is most likely to have which of the following effects?

© A) Decreased stability of mRNAs © B) Generation of hybrid (chimeric) mRNAs © C) Increased repertoire of gene products © D) Increased size of mRNAs © E) Rearrangement of cellular genome





25. Alteration of which of the following influenza virus proteins is most likely to result in altered reactivity to neutralizing antibodies?

© A) Hemagglutinin© B) Matrix protein© C) Nonstructural protein© D) Nucleoprotein© E) Polymerase





26. A 54-year-old man with alcoholism is brought to the emergency department because of a 10-day history of weakness, confusion, and shortness of breath. He drinks approximately three fourths of a liter of liquor daily. He appears wasted, and there is an odor of alcohol on his breath. His respirations are 32/min. Physical examination shows jaundice, abdominal distention, spider angiomata, and Tanner stage 2 gynecomastia. Laboratory studies show hypoalbuminemia and an increased serum estrogen- to-androgen ratio. The development of gynecomastia in this patient is mediated primarily by which of the following signal transduction pathways?

® A) Activation of phospholipase A2 and generation of arachidonic acid© B) Activation of phospholipase C and generation of inositol 1,4,5-trisphosphate© C) G protein-coupled activation of adenylyl cyclase0 D) Receptor dimerization and autophosphorylation of tyrosine residues© E) Transmembrane diffusion and binding of signaling molecule to transcription factor





27. A 6-month-old boy is brought to the emergency department because of pallor. He has been breast-fed exclusively since birth by his mother, who is a vegan and follows a strict vegetarian diet that excludes all meat, fish, and dairy products. Physical examination shows tachycardia and pallor; he appears malnourished. Laboratory studies show anemia. Plasma studies show an increased concentration of homocystine and a low-normal methionine concentration. Urine organic acid screening shows an increased concentration of methylmalonic acid. Treatment with which of the following is most likely to eliminate the methylmalonic aciduria in this patient?

© A) Cystine © B) Folic acid © C) Methionine© D) Vitamin B12 (cyanocobalamin)© E) Vitamin C (ascorbic acid)





28. A 17-year-old girl is evaluated because of a "boil" on her left shoulder. Examination shows an erythematous, painful, fluctuant lesion; a yellow-green liquid material isdrained surgically. The pain and erythema gradually subside. Which of the following cells contributes most to the tissue changes present in the lesion 5 days after drainage?

® A) Eosinophils © B) Lymphocytes © C) Macrophages © D) Neutrophils © E) Plasma cells





29. A 72-year-old man comes to the physician because of a 10-week history of weakness and shortness of breath with exertion. Physical examination shows marked pallor and a lack of erythema of the nail beds. Laboratory studies show:

Hemoglobin 5.2 g/dLLeukocyte count 5400/mm3 with a normal differentialReticulocyte count 0%Erythrocyte sedimentation rate 10 mm/h

Urinalysis shows no abnormalities. A peripheral blood smear is shown. Which of the following laboratory studies is most likely to show the earliest response to treatment in this patient?

A) Erythrocyte sedimentation rateB) Hemoglobin concentrationC) Leukocyte countD) Reticulocyte countE) Urinalysis

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30. The 45S rRNA precursor is cleaved into 18S, 5.8S, and 28S RNAs in which of the following?

© A) Endoplasmic reticulum © B) Endosome © C) Golgi complex © D) Lysosome © E) Nucleolus

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31. A 30-year-old man has a 3-day history of diarrhea with 6-8 watery stools per day. Tests of arterial blood are most likely to show which of the following sets of values?

Pco2 HC03"

pH (mm Hg) (mEq/L)A) 7.30 28 15B) 7.30 55 27C) 7.40 40 24D) 7.50 30 22E) 7.50 47 33

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32. During DNA replication in eukaryotic cells, which of the following occurs when topoisomerase I cleaves a phosphodiester bond in one DNA strand?

© A) Free rotation of the two sections of the DNA helix on either side of the nick © B) A recombination event between adjacent double helices© C) Removal and subsequent transfer of a small piece of DNA to another position on the chromosome © D) Removal of mismatched nucleotides that could result in deleterious mutations





33. A 32-year-old woman comes for a routine health maintenance examination. She has had intermittent constipation and flatulence. She says that there has been increasing tension with her husband, and she is uncertain about the viability of her marriage. Examination shows an ecchymosis on the right upper arm. Pelvic examination shows vaginal abrasions and is difficult to perform because of the patient's discomfort. She describes her mood as occasionally sad with no persistent depressed mood. She is moderately anxious and has a dysphoric affect. She has no suicidal or homicidal ideation or plan. Which of the following is the most appropriate next step in management?

© A) Scheduling a return visit in 2 weeks© B) Informing the patient about domestic violence shelters© C) Psychological testing© D) Individual psychotherapy© E) Marital therapy© F) Tricyclic anti depressant therapy





34. A 66-year-old man who is undergoing chemotherapy for leukemia has a 3-day history of progressive fever, headache, nausea, and deterioration of mental acuity. Analysis of cerebrospinal fluid shows lymphocytic pleocytosis, a normal glucose concentration, and a slightly increased protein concentration. The causal agent is presumptively identified by a positive India ink test and later confirmed with culture. Which of the following is the major virulence factor of the infecting organism producing this disease?

© A) Antigenic variation © B) Exotoxin© C) Immunoglobulin protease © D) Leukocidin © E) Polysaccharide capsule

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35. A 70-year-old man is brought to the emergency department because of fever, cough productive of blood-tinged sputum, and shortness of breath for 12 hours. Histemperature is 39.5°C (103.1 °F), and respirations are 36/min. Crackles are heard at the right lung base. Culture of sputum grows a-hemolytic, gram-positive diplococci. Which of the following characteristics of the causal organism best explains the development of pneumonia in this patient?

® A) Expression of a polysaccharide capsule © B) Intracellular sun/ival in macrophages © C) Production of endotoxin © D) Production of a potent ADP-ribosylating exotoxin © E) Production of a superantigen





36. The erythrocyte is prone to injury by reduced oxygen metabolites that are produced after spontaneous oxidation of oxyhemoglobin. Which of the following reactions or processes is most critical in protecting the erythrocyte from injury by these oxidation products?

© A) Dissociation of methemoglobin into metheme and globin chains © B) Glucose 6-phosphate dehydrogenase-catalyzed generation of NADPH © C) Inactivation of hydroxyl free radicals by (3-carotene © D) Synthesis of ubiquinone© E) Vitamin C-dependent reduction of methemoglobin to hemoglobin





37. Which of the following cellular junctions block the backflow of glucose from the basal side of the intestinal epithelium into the lumen of the gut?

© A) Adhering junctions © B) Desmosomes (maculae adherentes)© C) Gap junctions© D) Hemidesmosomes© E) Tight junctions (zonulae occludentes)

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38. A 19-year-old woman comes to the emergency department because she is afraid that she will kill herself. She has had recurrent episodes of self-mutilation, moodinstability, and poor impulse control over the past 5 years. Transient relief from these symptoms has been associated with multiple treatments, including antidepressants, anxiolytics, neuroleptics, and group therapy. She reports brief, intense romantic relationships with men and women. These findings are most consistent with which of the following?

© A) Acute drug reaction© B) Adjustment disorder with mixed disturbance of emotions and conduct © C) Alcohol withdrawal © D) Bipolar disorder © E) Borderline personality disorder © F) Dysthymic disorder© G) Major depressive disorder with psychotic features © H) Post-traumatic stress disorder © I) Schizophrenia © J) Separation anxiety disorder





39. A 5-day-old female newborn who is breast-fed is brought to the emergency department because of a 1 -day history of poor feeding, vomiting, and lethargy. Physical examination shows decreased responsiveness, hypotonia, and dehydration. There is a caramel-like odor in the diaper. Serum studies show a decreased glucose concentration, ketones, and metabolic acidosis. Metabolic studies of leukocytes show no conversion of [14C] leucine to 14C 02. An increased plasma concentration of which of the following substances is most likely in this patient?

© A) Alanine© B) Isovaleric acid© C) Methylmalonic acid© D) Phenylalanine© E) Propionic acid© F) Valine





40. A 30-year-old woman has cervical Pap smears showing cytopathic changes indicative of human papillomavirus type 16 infection. Which of the following is the most likely long-term consequence?

© A) Endometrial carcinoma © B) Papillary adenocarcinoma © C) Serous carcinoma © D) Small cell carcinoma © E) Squamous cell carcinoma





41. A 54-year-old man with squamous cell carcinoma of the lung comes to his physician's office because of constipation and gastrointestinal discomfort. He appears confused. Which of the following serum values is most likely to be increased?

© A) Calcium© B) Glucose© C) Magnesium© D) Nitric oxide© E) Potassium© F) Sodium© G) Uric acid





42. A 25-year-old primigravid woman at 3 months' gestation comes to the physician for her first prenatal visit. She requests an amniocentesis "to make me feel better that everything is all right with the baby." There is no family history of genetic disorders. Physical examination and laboratory studies show no abnormalities. The likelihood of finding an abnormality is low. The physician needs to balance which of the following ethical principles when deciding whether to grant this patient's request?

© A ) Autonomy versus maleficence © B) Autonomy versus utilitarianism © C) Beneficence versus deontology © D) Beneficence versus maleficence © E) Deontology versus utilitarianism





43. In a population, the frequency of the HLA-A locus allele (A*01) is 0.20 and the frequency of the HLA-B locus allele (B*08) is 0.20. In the same population, the frequency of the haplotype A*01, B*08 is 0.16. Which of the following terms best explains the population characteristics of the observed frequency of the A*01, B*08 haplotype?

® A) Linkage disequilibrium © B) Random assortment © C) Somatic mutation © D) Variable expressivity




44. Prostacyclin (PGI2) synthesized by the endothelial cells promotes which of the following?

© A ) Adhesion of platelets © B) Expression of selectins © C) Priming of leukocytes © D) Production of nitric oxide © E) Vasodilation

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45. A 2-year-old boy developed the vesicular lesions shown 2 days ago. Which of the following best describes the virus causing the lesions?

Nucleic AcidNuclear Capsid

SymmetryEnvelopePresent

® A) Double-stranded RNA icosahedral yes© B) Double-stranded RNA helical yes© C) Double-stranded RNA icosahedral no© D) Single-stranded RNA icosahedral no© E) Single-stranded RNA icosahedral yes

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46. A 7-year-old child with mental retardation is seen because of severe behavior problems in school and self-directed aggressive behavior. The patient is diagnosed with a complete deficiency of hypoxanthine-guanine phosphoribosyltransferase. This defect most likely results in the accumulation of which of the following metabolites in serum?

© A) Adenine© B) Cytosine© C) Guanine© D) Urea© E) Uric acid

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47. A 1 -year-old boy is brought to the physician by his mother for a well-child examination. She says he has no interest in toilet training. He is at the 30th percentile for height and weight. He has a vocabulary of about 10 words and recently began walking on his own. His mother consumed alcohol "several times" during her first trimester of pregnancy. Which of the following best describes the development of this boy?

Motor LanguageA) Delayed delayedB) Delayed normalC) Normal delayedD) Normal normal





48. A 40-year-old man has had progressive shortness of breath for 3 years. He has smoked 2 packs of cigarettes daily for 20 years. Examination of the bronchial mucosa obtained on biopsy shows ciliated, pseudostratified glandular epithelium with interspersed foci of normally maturing, stratified squamous epithelium overlying an intact basement membrane. Which of the following processes is the most likely explanation for these findings?

® A) Glandular dysplasia © B) Glandular hyperplasia © C) Glandular metaplasia © D) Squamous dysplasia © E) Squamous hyperplasia © F) Squamous metaplasia

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49. A 4-year-old boy is brought to the physician by his parents because of delayed speech and odd behaviors such as hand flapping. His mother has a learning disability, and his maternal uncle has mental retardation. Physical examination shows macrocephaly, large ears, and a prominent chin. He has a 3-word vocabulary. Which of the following studies is most likely to confirm the diagnosis?

® A) Detection of expanded trinucleotide repeat © B) Extended prometaphase banding © C) Fluorescence in situ hybridization © D) Polymorphism analysis © E) Subtelomeric deletion analysis





50. Which of the following is required from the diet and functions to protect tissues from the deleterious effects of free radicals?

© A) Arachidonicacid © B) Dehydroascorbic acid © C) Reduced glutathione © D) Vitamin B1 (thiamine)© E) Vitamin E


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