a. Compound A deficient, compound E from CO₂ and NH₄⁺

b. Compound B deficient, compound E from CO₂ and NH₄⁺

c. Compound C deficient, compound A from CO₂ and NH4₄⁺

d. Compound C deficient, compound B from CO₂ and NH4₄⁺

e. Compound E deficient, compound A from CO₂ and NH4₄⁺

100. A newborn Caucasian girl is the product of a normal gestation and delivery, feeding avidly until age 36 hours. Her mother reports less interest in breastfeeding, and she becomes lethargic over a period of 4 to 6 hours, prompting transfer to intensive care, initiation of antibiotics for possible sepsis, and laboratory testing. An elevated serum ammonia is documented at 500 μmol/L (normal of 30-50). She is placed on glucose infusion plus a compound from the figure below Question 99 that “primes” the urea cycle. Which of the compounds in the figure would accomplish some removal of ammonia and increase substrate availability at the beginning of the cycle (“prime” the cycle)?

a. Compound A

b. Compound B

c. Compound C

d. Compound D

e. Compound E

101. Certain organic acidemias or fatty acid oxidation disorders will also involve elevated ammonia. This relates to the location of reactions of the urea cycle, occurring in which of the following?

a. In the cytosol

b. In lysosomes

c. In the mitochondrial matrix

d. In the mitochondrial matrix and the cytosol

e. In peroxisomes

102. A 23-year-old Caucasian female is found to have elevated blood pressure on her routine obstetric checkup at 8 months gestation, and testing by her obstetrician demonstrates anemia with hemolysis, elevated liver enzymes, and low platelets that are characteristic of disease represented by the acronym HELLP syndrome. The female is hospitalized and fetal maturity tests are performed that allow elective premature delivery. The female quickly recovers but the premature newborn has a dilated heart and elevated liver enzymes that are characteristic of a defect in long-chain fatty acid oxidation. The potential enzyme deficiencies are those responsible for sequential oxidation of fatty acids, which include which of the following?

a. Dehydrogenase, hydratase, dehydrogenase, and thiolase

b. Transacylase, synthase, and reductase

c. Hydratase, reductase, and thioesterase

d. Thioesterase, dehydrogenase, and thiolase

e. Dehydrogenase, thiolase, and thioesterase

103. A 30-year-old African American female is admitted with a diagnosis of diabetic ketoacidosis. She had onset of juvenile (type I) diabetes at age 16 and has done well until attendance at a destination wedding altered her diet and insulin habits. Which of the following would best apply to her liver metabolism upon admission?

a. Increased glucose uptake, increased fatty acid oxidation, and decreased acetone synthesis

b. Increased glucose uptake, decreased fatty acid oxidation, and increased β-hydroxybutyrate synthesis

c. Decreased glucose uptake, increased fatty acid oxidation, and increased acetone synthesis

d. Increased glucose uptake, increased fatty acid oxidation, and increased acetoacetate synthesis

e. Increased glucose uptake, increased fatty acid oxidation, and decreased acetoacetate synthesis

104. Which of the following enzymes is most important in regulating lipogenesis?

a. Acetyl-CoA carboxylase

b. Medium-chain acetyl-CoA dehydrogenase

c. Short-chain enoyl reductase

d. Long-chain enoyl hydratase

e. 3-Ketoacyl reductase

105. Which of the following is the important reactive group of glutathione in its role as an antioxidant?

a. Serine

b. Sulfhydryl

c. Tyrosine

d. Acetyl-CoA

e. Carboxyl

106. Which of the following processes generates the most ATP?

a. Citric acid cycle

b. Fatty acid oxidation

c. Glycolysis

d. Pentose phosphate pathway

e. Glycogenolysis

107. A 3-year-old Caucasian girl is brought into the emergency room while you are on duty. She is cold and clammy and is breathing rapidly. She is obviously confused and lethargic. Her mother indicates she has accidentally ingested automobile antifreeze while playing in the garage. Following gastrointestinal lavage and activated charcoal administration, which of the following treatments should you immediately initiate?

a. Intravenous infusion of oxalic acid

b. Nasogastric tube for ethanol administration

c. Flushing out the bladder via a catheter

d. Intramuscular injection of epinephrine

e. Simply waiting and measuring vital signs

108. After finding that infants, particularly those with prematurity, are vulnerable to fatty acid deficiencies, major manufacturers began supplementing their infant formulas with these compounds. Which of the following is a nutritionally essential fatty acid along with its usual dietary source?

a. Eicosapentaenoic acid—plants

b. Linoleic acid—plants

c. Oleic acid—animals

d. Palmitoleic acid—animals

e. Linolenic acid—animals

109. A 62-year-old Caucasian male develops episodes of incoordination and slurred speech. His wife notes that he seems depressed and argumentative. His physician diagnoses multiple sclerosis, which is best described as which of the following?

a. Demyelinating disease with loss of phospholipids and ceramide from brain and spinal cord

b. Lipid storage disease with loss of sphingolipids and ceramide from brain and spinal cord

c. Lipid storage disease with loss of sphingolipids and gangliosides from brain and spinal cord.

d. Demyelinating disease with loss of phospholipids and sphingolipids from brain and spinal cord

e. Lipid storage disease with accumulation of sphingolipids in brain

110. Children with very long or long chain fatty acid oxidation disorders are severely affected from birth, while those with short- or medium-chain oxidation defects may be asymptomatic until they have an intercurrent illness that causes prolonged fasting. The severe symptoms of longer-chain diseases are best explained by which of the following statements?

a. Longer-chain fatty acids inhibit gluconeogenesis and deplete serum glucose needed for brain metabolism.

b. Glycogen is the main fuel reserve of the body but is quickly depleted with fasting.

c. Starch is an important source of glucose and is inhibited by high fatty acid concentrations.

d. Triacylglycerols are the main fuel reserve of the body and are needed for energy production in actively metabolizing tissues.

e. Longer-chain fatty acids form micelles and block synapses.

111. A 56-year-old Caucasian male with chronic alcoholism is admitted with hematochezia (bright red blood in stools) and hematemesis (bloody vomitus). Transfusions and esophageal tube pressure fail to maintain his blood pressure, and he dies from shock and cardiac failure. Autopsy would expect to show which of the following?

a. Normal liver with excess chylomicrons

b. Cirrhotic liver with excess HDL

c. Fatty liver with excess LDL

d. Fatty liver with VLDL

e. Cirrhotic and fatty liver with excess triacylglycerol

112. Niemann-Pick disease (MIM*257220), like other neurolipidoses, presents in infancy or childhood with plateauing of development and neurologic regression. The accumulating substance is a phospholipid made in which of the following steps in the figure below?

a. Step A

b. Step B

c. Step C

d. Step D

e. Step E

113. A 10-year-old Caucasian girl presents with chest pain and unusual skin patches over her elbows and knees. Her father died of a heart attack at age 35 and her mother is known to have high cholesterol. Her physician suspects familial hypercholesterolemia (MIM*144010) in the parents with homozygous severe disease in the daughter. This disease results from mutations in the receptor for low-density lipoprotein (LDL) or the ligand portion of its apoprotein coat, which is which of the following?

a. A-I

b. B-48

c. C-II

d. B-100

e. E

114. A 45-year-old Caucasian male is found to have a serum cholesterol of 300 mg/dL (normal <200 depending on criteria) after a 12-hour fast. Which of the following lipoproteins would contribute to plasma cholesterol following a 12-hour fast?

a. Very low density lipoproteins (VLDLs) and low-density lipoproteins (LDLs)

b. High-density lipoproteins (HDLs) and low-density lipoproteins (LDLs)

c. Chylomicrons and very low density lipoproteins (VLDLs)

d. Chylomicron remnants and very low density lipoproteins (VLDLs)

e. Low-density lipoproteins (LDLs) and adipocyte lipid droplets

115. A 2-day-old Caucasian male neonate with meconium ileus (plugging of the small intestine with meconium or fetal stool) is found to have air in the bowel wall (pneumatosis intestinalis) and free air in the abdomen. Antibiotics are begun for suspected peritonitis, and emergency surgery is performed to remove the diseased intestinal segment and heal the intestinal perforation that led to air in the abdomen. Because the gut must be kept at rest for healing, meconium peritonitis was usually fatal until parenteral alimentation solutions were developed. Hyperalimentation consists of essential amino acids and other metabolites that provide a positive calorie balance while keeping the bowel at rest. The alimentation solution must be kept to a minimum of metabolites because of its high osmotic load that necessitates frequent changing of intravenous sites or catherization of a large vein. Which of the following amino acids could be excluded from the alimentation solution?

a. Cysteine

b. Phenylalanine

c. Histidine

d. Methionine

e. Tryptophan

116. Leukocyte samples isolated from the blood of a newborn Caucasian boy are homogenized and incubated with ganglioside GM₂. Approximately 47% of the expected normal amount of N-acetylgalactosamine is liberated during the incubation period. These results indicate which of the following regarding this infant?

a. He is a heterozygote (carrier) for Tay-Sachs disease.

b. He is homozygous for Tay-Sachs disease.

c. He has Tay-Sachs syndrome.

d. He will most likely have mental deficiency.

e. He has relatively normal β-N-acetylhexosaminidase activity

117. A 4-year-old boy of Middle-Eastern ancestry is known to have inherited favism, a sensitivity to fava beans due to glucose-6-phosphate dehydrogenase deficiency (MIM*305900). Which of the following indicates the primary pathway affected by this deficiency and the pathway secondarily affected because one of its energy substrates will be deficient?

a. Pentose phosphate pathway, fatty acid synthesis

b. Pentose phosphate pathway, fatty acid oxidation

c. Citric acid cycle, fatty acid oxidation

d. Citric acid cycle, glycolysis

e. Glycolysis, citric acid cycle

118. Which enzyme catalyzes the only step of fatty acid oxidation that requires energy?

a. Acyl-CoA dehydrogenase

b. Acyl-CoA synthetase

c. Δ2-Enoyl-CoA hydratase

d. L(+)-3-Hydroxyacyl-CoA dehydrogenase

e. Thiolase

119. Adults with liver disease or milder urea cycle defects often exhibit neurologic symptoms (confusion, memory loss, and motor incoordination) when interval high-protein meals or anorexia with protein catabolism elevates their serum ammonia. Ammonia intoxication is most obvious in neonates with severe urea cycle defects, manifest by lethargy and coma. Given that the cerebral cortex is a very active tissue with high-energy requirements, which of the following consequences of hyperammonemia are most likely responsible for cerebral symptoms?

a. Decreased glutamine, increased carboymal phosphate synthase activity

b. Increased α-ketoglutarate, increased arginase activity

c. Decreased glutamine, increased arginase activity

d. Increased glutamine, increased carbamoyl phosphate synthase activity

e. Decreased α-ketoglutarate, increased arginase activity

120. Which of the following transamination reactions produces an intermediate that will directly facilitate oxidative phosphorylation as well as gluconeogenesis?

a. Asparagine to aspartate to oxaloacetate

b. Cystine to cysteine

c. Lysine to glutaryl-CoA

d. Serine to glycine

e. Methionine to cystine

121. Which of the following is not used in the synthesis of fatty acids?

a. ATP

b. Cobalamin (vitamin B₁₂)

c. FADH₂

d. HCO₃^–

e. NADPH

122. Which of the diagrammatic structures below models the configuration of lipids emulsified prior to hydrolysis during digestion?

a. Structure A

b. Structure B

c. Structure C

d. Structure D

e. Structure E

123. A 36-hour-old African American boy is evaluated because of inability to breast-feed and found to have severe hypotonia (low muscle tone). The child lays in a frog leg posture with minimal spontaneous movements, and the head and legs dangle to the bed when suspended by his stomach. A large anterior fontanel is noted, and initial laboratory tests indicate elevated liver enzymes. The physician suspects Zellweger syndrome (MIM*214100), an end phenotype reflecting peroxisome dysfunction that may be caused by mutations in several different peroxisomal membrane protein genes. The diagnosis is confirmed by demonstrating elevated plasma levels of very long chain fatty acids and of erythrocyte plasmalogens. Which of the following compounds is the starting point of ether lipid and plasmalogen synthesis?

a. Acetyl-CoA

b. Pyruvate

c. Dihydroxyacetone phosphate

d. Malonyl-CoA

e. Palmitoyl-CoA

124. A 5-year-old Caucasian girl presents to the emergency room for evaluation of respiratory distress. She has seemed tired for the past week in that she does not play after school and goes to bed without prompting. The presiding physician obtains a basic metabolic panel that shows glucose of 250 mg/dL (normal 70-100) and a pH of 7.1. Urinalysis using a standard reagent strip is negative for nitrites and white blood cells that indicate infection but is strongly positive for the presence of ketones. The physician concludes that the child has likely diabetic ketoacidosis and that the respiratory distress is due to Kussmaul breathing—reflexive deep respirations that attempt to compensate for the acidosis by lowering carbon dioxide. Which of the following are “ketone bodies” that registered positive on the urine reagent strip for ketones in this child?

a. Acetone and ethanol

b. β-Hydroxybutyrate and acetoacetate

c. Pyruvate and lactate

d. Fumarate and succinate

e. Oxaloacetate and pyruvate

125. Gangliosides and receptors for hormones such as glucagon can be found in which of the following structures?

a. Plasma membrane

b. Mitochondria

c. Lysosomes

d. Endoplasmic reticulum

e. Ribosomes

126. Which of the following is the major source of extracellular cholesterol for human tissues?

a. Very low density lipoproteins (VLDLs)

b. Low-density lipoproteins (LDLs)

c. High-density lipoproteins (HDLs)

d. Albumin

e. γ-Globulin

127. Which amino acid can be converted to an intermediate of the citric acid cycle and can be directly converted to urea?

a. Ornithine

b. Lysine

c. Arginine

d. Glutamate

e. Tyrosine

128. When the liver is actively synthesizing fatty acids, a concomitant decrease in β-oxidation of fatty acids is due to which of the following?

a. Inhibition of a translocation between cellular compartments

b. Inhibition by an end product

c. Activation of an enzyme

d. Detergent effects

e. Decreases in adipocyte lipolysis

129. A 4-year-old African American girl presents in the clinic with megaloblastic anemia (fewer red blood cells that are larger than normal) and failure to thrive. Blood chemistries reveal orotic aciduria (MIM*258900). Enzyme measurements of white blood cells reveal a deficiency of the pyrimidine biosynthesis enzyme orotate phosphoribosyltransferase and abnormally high activity of the enzyme aspartate transcarbamoylase. Which of the following treatments will reverse all symptoms if carried out chronically?

a. Blood transfusion

b. White blood cell transfusion

c. Dietary supplements of phosphoribosylpyrophosphate (PRPP)

d. Oral thymidine

e. Oral uridine

130. A 1-year-old Hispanic boy has a normal birth and infantile history except for delay in sitting up, crawling, and standing (delayed motor milestones). He begins the unusual habit of chewing on his fingers and lips and, in one instance, bites through the lip and leaves a large wound. His physician documents an elevated serum uric acid and suspects Lesch-Nyhan syndrome (MIM*300322). In considering potential therapy, the physician reads that purines are overproduced in gout and Lesch-Nyhan syndrome, causing hyperuricemia, yet the hypoxanthine analog allopurinol is only effective in gout. Allopurinol does not treat the neurologic symptoms of Lesch-Nyhan syndrome because it does not do which of the following?

a. Decrease de novo purine synthesis

b. Decrease de novo pyrimidine synthesis

c. Diminish urate synthesis

d. Increase phosphoribosylpyrophosphate (PRPP) levels

e. Inhibit xanthine oxidase

131. Which of the following would make hyperuricemia very unlikely in a patient?

a. Lesch-Nyhan syndrome

b. Gout

c. Xanthine oxidase hyperactivity

d. Carbamoyl phosphate synthase deficiency

e. Purine overproduction secondary to von Gierke disease

132. A 35-year-old Caucasian male presents to the emergency room with an acute abdomen (severe abdominal pain with tightness of muscles, decreased bowel sounds, and vomiting and/or diarrhea). He has been drinking, and a urine sample is unusual because it has a port-wine color. Past history indicates several prior evaluations for abdominal pain, including an appendectomy. The physician notes unusual neurologic symptoms with partial paralysis of his arms and legs. At first concerned about food poisons such as botulism, the physician recalls that acute intermittent porphyria may cause these symptoms (MIM*176000) and consults a gastroenterologist. Elevation of which of the following urinary metabolites would support a diagnosis of porphyria?

a. Urobilinogen and bilirubin

b. Delta-aminolevulinic acid and porphobilinogen

c. Biliverdin and stercobilin

d. Urobilin and urobilinogen

e. Delta-aminolevulinic acid and urobilinogen

133. Hyperuricemia in Lesch-Nyhan syndrome is due to a defect in which of the following pathways?

a. Purine biosynthesis

b. Pyrimidine biosynthesis

c. Purine salvage

d. Pyrimidine salvage

e. Urea cycle

134. Which of the following is the rate-controlling step of pyrimidine synthesis that exhibits allosteric inhibition by cytidine triphosphate (CTP)?

a. Aspartate transcarbamoylase

b. Hypoxanthine-guanine phosphoribosyl transferase (HGPRT)

c. Thymidylate synthase

d. Ribose-phosphate pyrophosphokinase

e. Xanthine oxidase

135. Which of the following compounds is a required substrate for purine biosynthesis?

a. 5-Methyl thymidine

b. Ara C

c. Ribose phosphate

d. 5-Phosphoribosylpyrophosphate (PRPP)

e. 5-FU

136. Which of the following compounds is joined with nicotinamide to form NAD and NADP, components that are deficient in niacin deficiency?

a. Cytosine monophosphate

b. Inosine diphosphate

c. Thymidine monophosphate

d. Hypoxanthine monophosphate

e. Adenosine diphosphate

137. A hitherto unknown disease is suggested by a 28-year-old male who has reducing substances in his urine, mild liver disease, and decreased liver glycogen upon liver biopsy. Which of the following metabolites would be the best candidate for measurement as a clue to the cause of disease?

a. Glucose 1-phosphate

b. Fructose 6-phosphate

c. Fructose 1,6-bisphosphate

d. Cytosine diphosphate

e. Uridine diphosphate

Stay updated, free articles. Join our Telegram channel

Join