KAPLAN

Question 1

Two weeks after an episode o f the flu, an 8-year-old boy with IDDM is brought to the emergency room in a coma. His breathing is rapid and deep, and his breath has a fruity odor. His blood glucose is 36.5 mM (normal: 4-6 mM [70-110 mg/dL]). The physician administers IV fluids, insulin, and potassium chloride. A rapid effect of insulin in this situation is to stimulate
A. gluconeogenesis in the liver
B. fatty acid release from adipose
C. glucose transport in muscle
D. ketone utilization in the brain
E. glycogenolysis in the liver

Answer 1

C

Question 2

An alcoholic has been on a 2-week drinking binge during which time she has eaten little and has become severely hypoglycemic. Which additional condition may develop in response to chronic, severe hypoglycemia?
A. Glycogen accumulation in the liver with cirrhosis
B. Thiamine deficiency
C. Ketoacidosis
D. Folate deficiency E. Hyperuricemia

Answer 2

c

Question 3

After a routine physical exam and blood work, a woman with a normal weight for her height was advised that her lipid profile showed an eleva­ tion of blood triglycerides. The doctor advises the patient to lower fat con­ sumption which disappoints her since she avidly consumes whole milk. The woman consults a nutritionist, who states that whole milk is 3.5% fat, which corresponds to approximately 1 1 g of fat in an 8 ounce serving. If she switches to drinking skim milk (nonfat), approximately how much addi­ tional grams of carbohydrates should she consume to make up for the loss of fat in the 8 ounce serving?
A. 5 grams
B. 11grams
C. 15 grams
D. 25 grams
E. 35 grams

Answer 3

D

Question 4

A breast-fed infant begins t o vomit frequently and lose weight. Several days later she is jaundiced, her liver is enlarged, and cataracts are noticed in her lenses. These symptoms are most likely caused by a deficiency of
A. galactose 1-P uridyltransferase
B. lactase
C. glucose-6-phosphatase
D. galactokinase
E. aldolase B

Answer 4

A

Question 5

Following an early-morning run, a 29-year-old man consumes an all­ American breakfast consisting of cereal, eggs, bacon, sausage, pancakes with maple syrup, doughnuts, and coffee with cream and sugar. Which of the following proteins will most likely be activated in his liver after breakfast?
A. Cytoplasmic PEP carboxykinase
B. Plasma membrane GLUT-4 transporter
C. Cytoplasmic phosphofructokinase-2
D. Mitochondrial carnitine transporter
E. Cytoplasmic glycogen phosphorylase

Answer 5

C

Question 6

A 55-year-old alcoholic was brought to the emergency department by his friends. During their usual nightly gathering at the local bar, he had passed out and they had been unable to revive him. The physician ordered an injection of thiamine followed by overnight parenteral glucose. The next morning the patient was alert and coherent, serum thiamine was normal, and blood glucose was 73 mg/dL (4 mM). The IV line was removed, and he was taken home.
4. Which of the following enzymes is thiamine-dependent and essential for glucose oxidation in the brain?
A. Transketolase
B. Transaldolase
C. Succinyl-CoA thiokinase
D. Acetyl-CoA carboxylase
E. Pyruvate dehydrogenase
5. At the time of discharge from the hospital, which of the following proteins would have no significant physiologic activity in this patient?
A. Malate dehydrogenase
B. Glucokinase
C. a-Ketoglutarate dehydrogenase
D. GLUT 1 transporter
E. Phosphofructokinase- 1

Answer 6

E
B

Question 7

During a myocardial infarction, the oxygen supply to an area of the heart is dramatically reduced, forcing the cardiac myocytes to switch to anaero­ bic metabolism. Under these conditions, which of the following enzymes would be activated by increasing intracellular AMP?
A. Succinate dehydrogenase
B. Phosphofructokinase- 1
C. Glucokinase
D. Pyruvate dehydrogenase
E. Lactate dehydrogenase

Answer 7

B

Question 8

A 40-year-old African American man is seen in the emergency room for a severe headache. His blood pressure is 180/1 10 mm Hg, and he has evidence ofretinal hemorrhage. An infusion of nitroprusside is given.
Which of the following enzymes is affected most directly by the active metabolite of this drug?
A. Phospholipase A2
B. Cyclic AMP phosphodiesterase
C. Guanylate cyclase
D. Cyclic GMP phosphodiesterase
E. Phospholipase C
When nitroprusside is given in higher than usual doses, it may be accom­ panied by the administration of thiosulfate to reduce potential toxic side effects. Which complex associated with electron transport or oxidative phosphorylation is most sensitive to the toxic byproduct that may accu­ mulate with high doses of nitroprusside?
A. NADH dehydrogenase
B. Succinate dehydrogenase
C. Cytochrome b!c1
D. C0ytochrome a/a3
E. FF1ATPsynthase

Answer 8

C
D

Question 9

A patient has been exposed to a toxic compound that increases the perme­ ability of mitochondrial membranes for protons. Which of the following events in liver cells would you expect to occur?
A. Increased ATP levels
B. Increased F i F0 ATP synthase activity
C. Increased oxygen utilization
D. Decreased malate-aspartate shuttle activity
E. Decreased pyruvate dehydrogenase activity

Answer 9

C

Question 10

A. Citrate shuttle
B. Glycerolphosphate shuttle
C. Malate-aspartate shuttle
D. Carnitine shuttle
E. Adenine nucleotide shuttle

5. Required for cholesterol and fatty acid synthesis in hepatocytes.
6. Required for the hepatic conversion of pyruvate to glucose.

Answer 10

A
C

Question 11

A liver biopsy is done o n a child with hepatomegaly and mild fasting hypo­ glycemia. Hepatocytes show accumulation of glycogen granules with single glucose residues remaining at the branch points near the periphery of the granule. The most likely genetic defect is in the gene encoding a(n):
A. a-1,4 phosphorylase
B. a-l,4:a-l,4 transferase
C. phosphoglucomutase
D. a-1,6 glucosidase
E. lysosomal a-1,4 glucosidase

Answer 11

D

Question 12

When fatty acid beta-oxidation predominates i n the liver, mitochondrial pyruvate is most likely to be
A. carboxylated to phosphoenolpyruvate for entry into gluconeogenesis
B. oxidatively decarboxylated to acetyl CoA for entry into ketogenesis
C. reduced to lactate for entry into gluconeogenesis
D. oxidatively decarboxylated to acetyl CoA for oxidation in Krebs cycle
E. carboxylated to oxaloacetate for entry into gluconeogenesis

Answer 12

E

Question 13

When adipose tissue stores triglyceride arriving from the liver or intestine, glycolysis must also occur in the adipocyte. Which of the following products or intermediates of glycolysis is required for fat storage?
A. Glycerol
B. Glucose 6-phosphate
C. Pyruvate
D. Acetyl-CoA
E. Dihydroxyacetone phosphate

Answer 13

E

Question 14

Abetalipoproteinemiaisageneticdisordercharacterizedbymalabsorptionofdietary lipid, steatorrhea (fatty stools), accumulation of intestinal triglyceride, and hypoli-poproteinemia. 3. A deficiency in the production of which apoprotein would most likely account for this clinical presentation?
A. ApoB-100
B. ApoB-48 c. ApoC-II
D. ApoA-I
E. ApoE
4. Patients with abetalipoproteinemia exhibit membrane abnormalities in their erythrocytes with production of acanthocytes (thorny-appearing cells). This unusual red cell morphology would most likely result from malabsorption of
A. palmitic acid
B. ascorbic acid
c. arachidonic acid
D. folic acid
E. linoleic acid

Answer 14

B
E

Question 15

A patient with a history of recurring attacks of pancreatitis, eruptive xan­ thomas, and increased plasma triglyceride levels (2,000 mg/dL) associated with chylomicrons, most likely has a deficiency in
A. lipoprotein lipase
B. LDL receptors
c. HMG-CoA reductase D. apoB-48
E. apoB-100 receptor

Answer 15

A

Question 16

Uncontrolled phagocytosis of oxidized LDL particles is a major stimulus for the development of foam cells and fatty streaks in the vascular suben­ dothelium. This process may be inhibited by increased dietary intake of
A. vitamin E
B. vitamin B6
C. vitamin D
D. vitamin B 1 2
E. vitamin K

Answer 16

A

Question 17

A 42-year-old man presents with a chief complaint of intermittent claudication during exercise. His family history is significant for the presence of cardiovascular disease on his father’s side, but not on his mother’s side. Physical exam reveals xan­ thelasmas and bilateral tendon xanthomas. A plasma lipid profile reveals a choles­ terol level of 340 mg/dL, with a high LDL/HDL ratio. He is given instructions for dietary modifications and a prescription for simvastatin.
7. The clinical findings noted in this patient are most likely caused by deficient production of
A. lethicin cholesterol acyltransferase
B. apoB-100 receptors
C. fatty acyl-CoA synthetase
D. VLDL from LDL
E. cholesterol ester transfer protein
8. The anticholesterolemic action of simvastatin is based on its effectiveness as a competitive inhibitor of the rate-limiting enzyme in cholesterol biosyn­ thesis. The reaction product normally produced by this enzyme is
A. squalene
B. methylmalonate
C. lanosterol
D. mevalonate
E. acetoacetate

Answer 17

B
D

Question 18

A 20-year-old man is taken to the university clinic to determine the cause of recurring hyperlipidemia, proteinuria, and anemia. Fasting blood tests reveal slightly elevated concentrations of unesterified cholesterol and phos­ phatidylcholine. The patient is given a 100 gram chocolate bar and blood lipid levels are monitored hourly. Results reveal significantly increased levels of unesterified cholesterol and phosphatidylcholine for extended periods. A deficiency of which of the following proteins is most likely to be associated with the observations in this patient?
A. Acyl-CoA:cholesterol acyltransferase (ACAT)
B. Apoprotein A- 1
C. Apoprotein B48
D. Apoprotein BlOO
E. Lipoprotein lipase

Answer 18

B

Question 19

A child is diagnosed with a congenital deficiency of medium-chain acyl­ CoA dehydrogenase activity. Which of the following signs or symptoms would most likely occur upon fasting in this child?
A. Hypolacticacidemia
B. Ketoacidosis
C. Hyperglycemia
D. Dicarboxylic acidosis
E. Hyperchylomicronemia

Answer 19

D

Question 20

A 3-year-old child complains o f muscle pain and weakness while in the playground and is admitted to the hospital for examination. Tests reveal slight hepatomegaly and cardiomegaly. A liver biopsy shows extreme but nonspecific fatty changes, and a muscle biopsy contains large amounts of cytoplasmic vacuoles containing neutral lipid. A one-day fast is per­ formed and shows a drop in blood glucose levels without a corresponding production of ketone bodies. The pH of the blood is normal. Which of
the following diagnoses might account for this child’s problems?
A. Bilirubin diglucuronide transporter deficiency
B. Glucose 6-phosphatase deficiency
C. Mitochondrial 3-hydroxy 3-methylglutaryl-CoA synthase deficiency
D. Systemic carnitine deficiency
E. Vitamin D deficiency

Answer 20

D

Question 21

Which enzymes are responsible for producing the direct donors ofnitrogen into the pathway producing urea?
A. Arginase and argininosuccinate lyase
B. Xanthine oxidase and guanine deaminase
C. Glutamate dehydrogenase and glutaminase
D. Argininosuccinate synthetase and ornithine transcarbamoylase
E.Aspartate aminotransferase and carbamoyl phosphate synthetase

Question 22

Two days after a full-term normal delivery, a neonate begins to hyperven­ tilate, develops hypothermia and cerebral edema, and becomes comatose. Urinalysis reveals high levels of glutamine and orotic acid. The BUN is below normal. Which enzyme is most likely to be deficient in this child?
A. Cytoplasmic glutaminase
B. Cytoplasmic carbamoyl phosphate synthetase
C. Cytoplasmic orotidylate decarboxylase
D. Mitochondrial carbamoyl phosphate synthetase
E. Mitochondrial ornithine transcarbamoylase

Question 23

A 49-year-old man with a rare recessive condition is at high risk for deep vein thrombosis and stroke and has had replacement of ectopic lenses. He has a nor­ mal hematocrit and no evidence of megaloblastic anemia.
280 �MEDICAL
7.
A mutation in the gene encoding which ofthe following is most likely to cause this disease?
A. Cystathionine synthase
B. Homocysteine methyltransferase
C. Fibrillin
D. Lysyl oxidase
E. Branched chain a-ketoacid dehydrogenase
Amino acid analysis of this patient’s plasma would most likely reveal an abnormally elevated level of
A. lysine
B. leucine
c. methionine D. omithine E. cysteine
A 56-year-old man with a history of genetic disease undergoes hip replace­ ment surgery for arthritis. During the operation the surgeon notes a dark pigmentation (ochronosis) in the man’s cartilage. His ochronotic arthritis is most likely caused by oxidation and polymerization of excess tissue
A.
homogentisic acid
B.
orotic acid
c.
methylmalonic acid
D.
uric acid
E.
ascorbic acid

Question 24

13. A woman 7 months pregnant with her first child develops anemia. Laboratory evaluation indicates an increased mean cell volume (MVC), hypersegmented neutrophils, and altered morphology of several other cell types. The most likely underlying cause of this woman’s anemia is
    A. folate deficiency
    B. iron deficiency
    C. glucose 6-phosphate dehydrogenase deficiency
    D. cyanocobalamin (B12) deficiency
    E. lead poisoning

Question 25

In response to a B12 deficiency, which of the additional conditions may develop in this patient if she is not treated?
A. Progressive peripheral neuropathy B. Gout
C. Wernicke-Korsakoff
D. Destruction of parietal cells
E. Bleeding gums and loose teeth