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Directions: The USMLE Step 1 exam tests the Basic Sciences. Designed for US Medical Student’s in their second year of Medical School, before their Clinical Rotations, International Medical Graduates will often struggle with going back to basics, and thinking like a pre-clinical student, rather than a qualified Physician. Look at the sample USMLE questions below and explore the sorts of questions you’ll face on the exam. The USMLE Step 1 exam questions are in Clinical Vignette format, meaning that you will be asked to pull on information from a number of different disciplines and organ systems and that you will be required to make a number of conclusions based on the limited information provided. This means if you do not have enough knowledge to make numerous conclusions on a topic then you’re likely to get the question wrong. You will see below a number of USMLE questions with multiple choice answers. There is one best answer and no negative marking on the USMLE exam, so we recommend you guess if you are unsure or running out of test time. Click on the get answer button to download the answers and explanations.
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the venous system carries oxygenated blood. On examination. and poor feeding. B. Which of the following describes the function of the ductus arteriosus during fetal life? A. From the pulmonary artery.Anatomy A neonate presents with tachycardia. tachypnea.com © Copyright Kaplan Test Prep and Admissions 2008 . Highly oxygenated blood from the right ventricle is ejected into the pulmonary artery. choices B. C.com | kaptest. and D are incorrect. the right ventricle is the “workhorse” of the circulatory system. In the fetus.europe@kaplan.Question 1 . a continuous murmur is auscultated. diaphoresis. London WC2H 0HA + 44 (0) 20 7930 3130 | www. C. Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road. It It It It It differentiates into the mitral valve shunts deoxygenated blood from the aorta to the pulmonary artery shunts deoxygenated blood from the pulmonary artery to the aorta shunts oxygenated blood from the aorta to the pulmonary artery shunts oxygenated blood from the pulmonary artery to the aorta Answers and Explanations E The ductus arteriosus shunts oxygenated blood from the pulmonary artery into the aorta. A patent ductus arteriosus is diagnosed. blood moves either into the ductus arteriosus (88%) or into the pulmonary circulation (12%). E. D.kaptesteurope. In the fetus. Thus.
London WC2H 0HA + 44 (0) 20 7930 3130 | www. requires which of the following? A. Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road. but not smooth muscle contraction. E. The two muscle types differ because skeletal muscle contraction. This depolarization opens Ca2+ channels on the sarcoplasmic reticulum. and the contractile properties of each are studied. allowing myosin and actin to bind.kaptesteurope. Isolated guinea pig intestine and skeletal muscle are stimulated. action potentials in the muscle cells depolarize T tubules. Ca2+ is released from the sarcoplasmic reticulum and binds calmodulin. B. In skeletal muscle. ATP binds to the myosin. Myosin attaches to another site on actin (power stroke) to shorten the sarcomere. actin (choice A) and myosin (choice C) are incorrect because these are present in both skeletal and smooth muscle. Smooth muscle contraction is different because there is no troponin.Question 2 . then ADP is released and the cycle repeats again as long as Ca2+ is bound to troponin. D. Calmodulin (choice B) and myosin lightchain kinase (choice D) are required for smooth muscle.europe@kaplan. C. The Ca2+ binds troponin on the thin filaments.Physiology An experiment is conducted to determine the difference between skeletal and smooth muscle contraction. Actin Calmodulin Myosin Myosin light-chain kinase Troponin Answers and Explanations E Skeletal muscle contractions are initiated by Ca2+ binding to troponin. causing a conformational change in myosin.com | kaptest. causing a conformational change in troponin that moves tropomyosin out of the way. The Ca2+ -calmodulin complex binds and activates myosin light-chain kinase. which then phosphorylates myosin and allows it to bind the actin. ATP is hydrolyzed to ADP. This action results in sarcomere shortening.com © Copyright Kaplan Test Prep and Admissions 2008 . and ADP remains attached to myosin. contraction. which allows myosin to be released from actin. whereas smooth muscle contractions are initiated by myosin light-chain phosphorylation. causing the release of Ca2+ stores into the intracellular fluid. Therefore. but not skeletal muscle.
A lack of folate prevents the conversion of homocysteine to methionine with subsequent accumulation of homocysteine.europe@kaplan. Although elevated serum levels of homocysteine have been linked to atherosclerothic disease. Vitamin B6. Arginine Folate Vitamin A Vitamin B1 Vitamin B6 Answers and Explanations B Hyperhomocysteinemia can lead to an increased risk of atherosclerotic disease. the exact mechanism is not well known. E. prevent neurotoxicity associated with isoniazid. or pyridoxine (choice E). does not participate in homocysteine metabolism. is not associated with hyperhomocysteinemia. thus leading to atherosclerosis.Biochemistry A 57-year-old man has crushing substernal chest pain for several hours. B. Upon admission to the emergency department. Vitamin B1. Chronic administration of which of the following will lower his serum homocysteine levels and possibly reduce his risk of subsequent infarcts? A. It can. Subsequent testing in the coronary care unit reveals that this patient has significant hyperhomocysteinemia.com | kaptest. One of the primary causes of hyperhomocysteinemia. London WC2H 0HA + 44 (0) 20 7930 3130 | www. which may have contributed to his infarction. physicians diagnose him with acute myocardial infarction. One current hypothesis suggests that homocysteine may have a cytotoxic and desquamative effect on endothelial cells. D.kaptesteurope. has been linked to both conditions. Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road. Allthough some scant evidence has shown that increasing intake of arginine (choice A) leads to reduction in the atherosclerosis. or thiamine (choice D). a lipid-soluble vitamin important for vision and skin integrity. folate deficiency.com © Copyright Kaplan Test Prep and Admissions 2008 . however. Thiamine deficiency results in psychosis. ophthalmoplegia. is not known to participate in homocysteine metabolism. and ataxia. Vitamin A (choice C). increasing serum arginine would not reduce levels of homocysteine. C.Question 3 .
who is HIV-positive. It is effective in killing the erythrocytic forms of this parasite. the man has been having increasing episodes of disorientation. C. which are visible by radiology or head CT. B. Amodiaquine (choice A) is a drug used in the treatment of malaria. it causes a subclinical lymphadenopathy resembling mononucleosis.europe@kaplan. Over the past month.com © Copyright Kaplan Test Prep and Admissions 2008 . iodoquinol is necessary. Amodiquine Iodoquinol Metronidazole Pyrimethamine plus sulfadiazine Trimethoprim sulfamethoxazole Answers and Explanations D This patient is suffering from Toxoplasma encephalitis. His partner tells the attending physician that the man has been unable to afford the prescribed antiretroviral drugs since he was terminated from his job a year ago. Toxoplasma gondii is the most common parasitic infection in the United States. is brought into emergency department by his partner. and as they multiply they cause increasing areas of necrosis (ringenhancing lesions). but if there is evidence of extraintestinal invasion. which cause the symptoms in humans. What is the treatment of choice? A.Question 4 . Routine blood testing reveals a CD4 count of 190/mm3. The parasites are intracellular in humans. Metronidazole is used against the luminal parasites. Iodoquinol (choice B) is the drug of choice for treatment of tissue-invasive Entamoeba histolytica. which is a common infection in full-blown AIDS. and a CT scan of the brain demonstrates ring-enhancing lesions.com | kaptest. In normal individuals.Microbiology A bank teller in New York City. with up to 70% of the population seropositive. Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road. E. The treatment of choice for Toxoplasma encephalitis is pyrimethamine plus sulfadiazine. and this evening he became aggressive and incoherent. but in immunodepressed individuals. most frequently causing damage to brain and retina. these inapparent infections can reactivate. and many HIV-positive patients are put on prophylaxis against this agent when their CD4 count falls below 200.kaptesteurope. London WC2H 0HA + 44 (0) 20 7930 3130 | www. D.
It is also used prophylactically in AIDS patients but would not be the drug of choice against Toxoplasma encephalitis. and leukotrienes.europe@kaplan. sensitized mast cells and basophils release histamines. IgA IgE IgG IgM T cells Answers and Explanations B Many reactions to plant stings.com | kaptest.Immunology A 3-year-old girl is stung by a bee while playing in the yard. an initial exposure to the antigen occurs. The consequences can be profound. and her mother finds her unconscious and cyanotic. animal stings. London WC2H 0HA + 44 (0) 20 7930 3130 | www. B.Metronidazole (choice C) is the drug of choice for the luminal phases of Entamoeba histolytica. and angioedema. C. initiating B-cell proliferation and formation of IgE antibodies. or immediate hypersensitivity reactions). Question 5 . urticaria. Which of the following mediated this girl’s reaction to the sting? A. E. kinins. In such reactions. D. Treatment for anaphylaxis is immediate administration of epinephrine. Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road. such as the vascular collapse seen in anaphylaxis.com © Copyright Kaplan Test Prep and Admissions 2008 . prostaglandins. When subsequent exposure occurs. Trimethoprim sulfamethoxazole (choice E) is the drug of choice for treatment of Pneumocystis carinii pneumonia in full-blown AIDS.kaptesteurope. or drugs are IgE-mediated responses (type 1. Such reactions include anaphylaxis. She is taken to the emergency department where epinephrine is administered and the girl recovers. as well as Giardia lamblia and Trichomonas vaginalis.
blood pressure is 110/70 mm Hg and there is pitting edema in the lower extremities. IgG (choice C) and IgM (choice D) participate in circulating humoral immunity with IgM participating in the acute phase of infection and IgG participating in the senescent phase of infection. B. and in secretions. as well as chronic humoral “maintenance”.kaptesteurope. They do not participate in acute hypersensitivity reactions. Light microscopic evaluation of a kidney biopsy is negative for any glomerular pathology. They do not participate in type 1 hypersensitivity reactions. T cells (choice E) are not involved in immediate hypersensitivity reactions. E.IgA (choice A) antibodies are secreted at mucosal surfaces. Which of the following lowing is the most likely diagnosis? A. The only significant past medical history is a streptococcal throat infection 3 weeks ago. Blood tests demonstrate elevated levels of cholesterol but decreased levels of albumin. as well as a small amount of periorbital swelling. London WC2H 0HA + 44 (0) 20 7930 3130 | www. The patient is treated and makes a full recovery. such as the gut lumen. Question 6 .com © Copyright Kaplan Test Prep and Admissions 2008 .Pathology A 6-year-old boy is evaluated for kidney disease. C.europe@kaplan. Acute nephritic syndrome Acute pyelonephritis Minimal change disease Postinfectious glomerulonephritis Rapidly progressive glomerular nephritis Answers and Explanations C Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road. D. On physical examination. The body denies any diarrhea or pain on urination.com | kaptest. such as tears and breast milk. Urine tests are positive for protein.
After quickly administering the antidote. Which of the following biochemical events does this nerve gas affect? A. On electron microscopy. urine may be positive for protein but not to the level seen in nephritic syndrome. he begins to experience severe spastic muscular paralysis. there is leukocyte infiltration involving all areas of the glomeruli. Light microscopic evaluation of minimal change disease. F. Acute pyelonephritis (choice B) represents an infection of the collection system. London WC2H 0HA + 44 (0) 20 7930 3130 | www. choice E) is associated with severe insults to the glomeruli. D. E. although he continues to exhibit muscular spasms for a longer time. is unremarkable. Within minutes. edema. giving the classic nephritic syndrome pattern (choice A).Minimal change disease (lipoid nephrosis) is the most common cause of nephrotic syndrome in children. Breakdown of a neurotransmitter Packaging of a neurotransmitter Receptor binding of a neurotransmitter Reuptake of a neurotransmitter Synaptic release of a neurotransmitter Synthesis of a neurotransmitter Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road.europe@kaplan. he soon recovers from his symptoms. On light microscopic evaluation. Rapidly progressive glomerulonephritis (RPGN.com © Copyright Kaplan Test Prep and Admissions 2008 . and hyperlipidemia. C. vomiting.kaptesteurope. bradycardia. with fever and costovertebral angle tenderness. B. Individuals with nephrotic syndrome waste large amounts of protein in the urine (>3 g/day). as the name suggests. There would be pain on urination. an atropine injection. effacement of the podocyte foot process can be noted. RPGN II can be postinfectious and is associated with the development of immune complexes. and excessive secretion of tears from his eyes and saliva from his mouth. Postinfectious glomerulonephritis (choice D) is associated with tea-colored urine.com | kaptest. hypotension.Pharmacology A chemist is accidentally exposed to an experimental nerve gas. They also have low serum albumin. It is also associated with hypertension. Question 7 .
Because nicotinic receptors are not affected by atropine. London WC2H 0HA + 44 (0) 20 7930 3130 | www. thereby potentiating the effects of this neurotransmitter. which is produced by Clostridium botulinum and is associated with home-canned food. The synthesis of ACh can be blocked by bromoacetylcholine (choice F). These drugs inhibit the breakdown of acetylcholine (ACh).Answers and Explanations A The nerve gas described is an acetylcholinesterase inhebitor. as well as such potent nerve gases as sarin or VX gas. including the reduction in heart rate and increased gastrointestinal motility. Vesamicol prevents the packaging of ACh into synaptic vesicles (choice B). causing spastic paralysis of skeletal muscles (versus flaccid paralysis. the nerve gas would be expected to stimulate the neuromuscular junction. as well as salivation and lacrimation. as well as the activation of parasympathetic effector sites via muscarinic ACh receptors.com | kaptest.kaptesteurope. Therefore.com © Copyright Kaplan Test Prep and Admissions 2008 . Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road. which would occur if neuromuscular activity is blocked) and overstimulation of parasympathetic responses. Among the actions of this neurotransmitter are stimulation of neuromuscular junctions via nicotinic ACh receptors.europe@kaplan. Acetylcholine is usually returned to the synapse in its metabolized form as choline. is botulinum toxin. The parasympathetic effects can be reversed by the use of atropine. the chemist will continue to manifest skeletal muscle effects until the drug is eliminated. Receptor antagonists would prevent the binding of a neurotransmitter to a receptor (choice C). which is an antagonist at muscarinic ACh receptors. An agent that prevents the synaptic release of acetylcholine (choice E). Drugs such as hemicholinium affect choline reuptake (choice D). causing flaccid paralysis. which shares a biochemical mechanism with many insecticides.
Definitive conclusions about the standard deviations and the variances cannot be made without additional data B. London WC2H 0HA + 44 (0) 20 7930 3130 | www. variance (s2). but the variances are different E.com © Copyright Kaplan Test Prep and Admissions 2008 . but the variances are equal Answers and Explanations C This questions tests the student’s understanding of the concepts of standard deviation (s). The standard deviations and the variances of both samples are equal D. the researchers examine the general properties of the resulting data. The standard deviations of both samples are different.Question 8 – Behavioral Science and Biostatistics A total of 1000 individuals with a body mass index (BMI) greater than 30 are recruited for a multicenter study focused on testing methods for controlling obesity. This examination reveals the following results: 95% of Sample in This Range Low High Control group 154 lb 213 lb Treatment group 133 lb 192 lb Using this information. An examination of the interval containing 95% of each group suggests which of the following? A.com | kaptest. and the constant percentage of cases within 2 standard Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road. Both groups have the same average weight at the start of the study. The weight of all study participants is assessed at the end of a 6-month trial.europe@kaplan. which is shown an educational video and given instructions on wight loss methods. The standard deviation of both samples is equal. Before formal statistical analyses are conducted. The standard deviations and the variances of both samples are different C.kaptesteurope. Study participants are randomly assigned to one of two groups: a treatment group. however. or a control group. the researchers decide to make some determinations about the standard deviation and the variance for the two groups. which is enrolled in a mentored weight loss program. and the average weights of treatment and control groups are compared.
recall that approximately 95% of cases in a normal curve will fall within 2 standard deviations of the mean. Because these presented ranges are the same. mean ±2s = 59 (or 4 standard deviations total). therefore. then their variances must be the same as well (if s1 = s2.com © Copyright Kaplan Test Prep and Admissions 2008 .com | kaptest.75 (or 59/4).kaptesteurope.deviations of the mean in the normal distribution.56. Kaplan Test Prep and Admissions – European Head Office 3-5 Charing Cross Road. First. Next. and the variance is =217.europe@kaplan. but notice that the standard deviation in both groups is 14. for both groups. the standard deviations (and the variances) for both groups must be the same. This means that if 2 standard deviations are the same. then s12 = s22). recall that the variance = (standard deviation)2. In both groups. The question does not ask for it. this range is 59. This suggests that the ranges presented in the above table constitute mean ±2s. London WC2H 0HA + 44 (0) 20 7930 3130 | www.
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