MD2 Nutrition Final Exam

A nutritionist explains to a patient that one unit of energy equals the amount needed to raise the temperature of 1 kilogram of water by 1°C. This unit of energy is known as:

Kilocalorie

A 40-year-old man with obesity is advised to reduce dietary fat intake. He eats a snack that contains 47% of its total calories from fat. The snack has 9 g of fat. How many kcal are provided by fat in this snack?

81 kcal

A 34-year-old woman wants to understand why her daily caloric needs are higher than expected. Her total energy expenditure (TEE) is found to be mostly determined by the energy needed to maintain essential body functions at rest. This component typically accounts for which percentage of TEE?

50-70%

A nutrition researcher is determining the average daily intake of Vitamin C that meets the needs of 50% of the population. Which dietary reference intake is she calculating?

EAR

A 6-year-old boy from a rural area presents with difficulty seeing at night. His mother says he bumps into objects when the lights are dim. Examination shows dry, scaly skin and Bitot spots on the conjunctiva. Which of the following biochemical processes is most impaired?

Regeneration of rhodopsin in retinal rods

A 40 year old man presents with headache, blurry vision, and nausea. Fundoscopy reveals papilledema. He has been taking large amounts of a nutritional supplement containing retinol for “immune support”. Which of the following additional findings is most likely?

Dry, itchy skin, and alopecia

A 22 year old woman presents after an abnormal fetal ultrasound. She routinely takes an online purchased isotretinoin supplement for acne. She is now 9 weeks pregnant. Ultrasound reveals micrognathia, low-set malformed ears, conotruncal cardiac defect, and a lumbosacral neural tube defect.

Disruption of HOX gene expression affecting neural crest & neural tube patterning

A 7 year old malnourished child from a refugee camp presents with progressive vision problems. The image below shows the appearance of his conjunctiva: Which stage of vitamin A deficiency is demonstrated

Bitot spots formation

A 14-month-old boy is brought to the clinic because of delayed motor milestones. His mother reports that he has difficulty standing without support and often seems irritable. She states that he is still exclusively breast-fed and spends very little time outdoors. Physical examination reveals

a. Frontal bossing

b. Widened wrists and ankles

c. Bowed legs (genu varum)

d. Rachitic rosary along the costochondral junctions

e. Delayed closure

Laboratory findings:

a. decreased calcium

b. decreased phosphate

c. increased alkaline phosphatase

d. increased parathyroid hormone

Which of the following is the most likely diagnosis?

Vitamin D Deficiency (Nutritional Rickets)

A 71-year-old woman with a long-standing history of type 2 diabetes and poorly controlled hypertension comes to the clinic due to worsening bone pain, difficulty rising from a chair, and fatigue. She also reports muscle cramps, increased susceptibility to fractures, and pruritus. She has end-stage renal disease and receives regular hemodialysis. Examination reveals diffuse bony tenderness over the ribs and pelvis.

Laboratory results:

Serum calcium: 7.4 mg/dL (low)

Phosphate: 6.2 mg/dL (high)

Alkaline phosphatase: elevated

25-hydroxyvitamin D: normal

1, 25-dihydroxyvitamin D: low

Which of the following mechanisms best explains these findings?

Decreased renal 1-alpha-hydroxylase activity

A 6-day-old male infant is brought to the emergency department due to bleeding from the umbilical stump and bloody stool. He was delivered at home without medical assistance, and his parents refused all newborn interventions, including vitamin K prophylaxis injection. The infant is exclusively breast-fed. On examination, he appears pale, with multiple bruises across the trunk and a small cephalohematoma.

Laboratory results show:

Prolonged PT

Prolonged aPTT

Normal platelet count

Normal Fibrinogen

Which of the following best explains this infant’s bleeding disorder?

Impaired gamma-carboxylation of glutamate residues

Vitamin E

A 35-year-old man enrolls in a metabolic nutrition study involving a diet severely deficient in several micronutrients for 6 weeks. He develops progressive fatigue, irritability, and tingling/burning sensations in his feet. He also reports muscle cramps, mild weakness climbing stairs, and occasional palpitations. On physical exam, he is mildly hypotensive with decreased ankle reflexes and distal neuropathy. Routine labs show normal electrolytes and no anemia.

A leukocyte enzyme assay shows reduced activity of the pyruvate dehydrogenase complex and α-ketoglutarate dehydrogenase complex. Which vitamin deficiency best explains these findings?

Vitamin B1 (Thiamine)

A 42-year-old man living in a rural area presents with chronic diarrhea, worsening skin rash, and difficulty concentrating. Physical examination shows a hyperpigmented, scaly rash on the backs of his hands and forearms in a distribution that worsens with sun exposure as shown in the picture. Neurologic exam reveals irritability and mild memory impairment.

Which vitamin deficiency is most likely responsible for his condition?

Vitamin B3 (Niacin)

A 47-year-old homeless man comes to the emergency department due to a "pins-and-needles" sensation in his legs. He also has painful lesions on his lips and come mouth. He has had no loss of consciousness, nausea, vomiting, or diplopia. The patient drinks alcohol heavily on a daily basis and has a history of intravenous heroin use. On physical examination, he appears unkempt and ill appearing. Temperature is 36.8 C (98.2 F), blood pressure is 146/90mm Hg, and pulse is 106/min. He has glossitis and angular stomatitis. Abdominal examination reveals hepatomegaly. Laboratory evaluation shows very low urinary riboflavin excretion. Activity of which of the following enzymes is most likely directly impaired in this patient?

Succinate dehydrogenase

A 2-month-old boy is brought to the emergency department due to irritability and vomiting. The patient is exclusively breastfed but has not been tolerating feeds since yesterday. Urine output has decreased. The mother has a history of obesity and had gastric bypass surgery several years prior to pregnancy. Temperature is 37°C (98.6°F), pulse is 190/min, and respirations are 60/min. The patient is in moderate respiratory distress and has an enlarged liver. Physical examination is otherwise normal. Chest radiography reveals cardiomegaly. Further workup shows impaired carbohydrate metabolism with increased serum levels of lactate and decreased erythrocyte transketolase activity. Which of the following additional enzymes is most likely to have impaired activity in this patient?

Pyruvate dehydrogenase

A 20-year-old woman comes to the clinic for evaluation of fatigue that has progressively worsened over the past month. The patient was recently diagnosed with celiac disease, but she has not strictly adhered to a gluten-free diet. Laboratory evaluation reveals macrocytic anemia with a low folate level but normal vitamin B12 level. Oral folic acid is prescribed. Which of the following biochemical changes is most likely to occur in this patient after starting treatment?

Decreased homocysteine, increased methionine, no change methylmalonic acid

A 20-year-old white male presented with anorexia, glossitis, and scanty hair on the scalp as shown in the picture below. The physician discovered that he was on a diet containing sixteen raw eggs daily for 18 months (as advised by a well meaning therapist to aid liver regeneration following a diagnosis of cirrhosis). All symptoms cleared after 2-5 days of parental vitamin therapy. Which protein found in raw eggs caused the vitamin deficiency and which is the vitamin deficient?

Avidin, biotin

A 45-year-old man with a diet limited to tea, crackers, and canned meat presents with fatigue, gum bleeding, and small purple spots on his legs. Physical exam reveals perifollicular hemorrhages, gingival swelling, and poor wound healing.

Which of the following biochemical reactions is impaired in this patient?

Hydroxylation of proline and lysine residues

Which of the following is classified as a trace element (micromineral) rather than a macro-mineral?

Zinc

Which of the following dietary components enhances the intestinal absorption of non-heme iron?

Vitamin C

A 22-year-old college student complains of fatigue and craving for ice. She follows a vegan diet and has heavy menstrual periods. Physical exam shows pale conjunctiva and spoon-shaped nails.

Laboratory findings:

Hemoglobin = 9 g/dL

MCV = 70 fL

Serum iron decreased

Ferritin decreased

TIBC decreased

Which of the following best describes the pathogenesis of this patient’s anemia?

Decreased heme synthesis due to iron deficiency

A 67-year-old man with long-standing rheumatoid arthritis presents with mild fatigue. Labs show: Hemoglobin = 10 g/dL; Serum Fe decreased; Ferritin increased; TIBC decreased. Which of the following mechanisms best explains these findings?

Cytokine-induced increase in hepcidin synthesis

Which nutrient deficiency is most strongly associated with periorificial dermatitis (around the mouth and anus as shown in given picture), alopecia, and poor wound healing?

Zinc

A 7-month-old boy is brought to the clinic for poor feeding, hypotonia, and delayed developmental milestones. On exam, he has sparse, brittle, “kinky” hair and pale skin. His parents state that he has frequent fractures and does not gain weight despite adequate feeding.

Laboratory studies:

Serum copper: low

Ceruloplasmin: low

Serum zinc: normal

Which of the following mechanisms best explains this infant’s condition?

Impaired copper transport due to ATP7A mutation

A 42-year-old woman who recently immigrated presents with fatigue, muscle pain, and episodes of shortness of breath. She lives in a region with selenium-deficient soil.

Exam reveals mild cardiomegaly.

Deficiency of which of the following enzymes is most likely responsible?

Glutathione peroxidase

A hospitalized patient has been receiving total parenteral nutrition (TPN) for 3 weeks after abdominal surgery.

He develops polyuria, polydipsia, and rising blood glucose levels despite no history of diabetes.

Which of the following trace elements is most likely deficient?

Chromium

A 2-month-old infant is brought for a routine checkup. He is exclusively breast-fed and is growing well. His birth weight has doubled.

Which of the following statements best explains the high energy requirement during early infancy?

The brain utilizes about 60% of total energy intake.

A 2-year-old child drinks 6 cups of cow’s milk daily and eats few solids. She develops pallor and irritability. She is most likely deficient in:

Iron

A 13-year-old boy has experienced a rapid increase in height and appetite over the past year. Which hormonal change primarily drives the increased protein synthesis during puberty?

IGF-1 stimulated by GH

A 72-year-old woman presents with progressive fatigue and tingling sensations in her feet. She has a long-standing history of reduced gastric acid secretion due to chronic gastric atrophy. Which nutrient is she MOST at risk of deficiency?

Vitamin B12

After carbohydrate digestion is complete, which of the following transporters helps in uptake of glucose across the mucosal cell?

SGLT-1 (Sodium dependent glucose transporter)

During lactose intolerance, bloating and flatulence occur due to the accumulation of gases in the colon. Which of the following best explains the origin of these gases?

Fermentation of unabsorbed lactose by colonic bacteria

A 6-year-old boy presents with intermittent ataxia, photosensitive rash, and emotional liability. Urinalysis reveals increased neutral amino acids. Dietary history shows adequate protein intake. Which step in protein utilization is defective?

Na+ dependent amino acid transport in the proximal tubule & intestine

A 44-year-old woman undergoes cholecystectomy for gallstones. After surgery, she experiences mild steatorrhea after large fatty meals. Which mechanism best explains this?

Reduced micelle formation due to lack of concentrated bile release

A 23-year-old male is brought to the emergency department with complaints of vomiting, abdominal pain and delirium. White lines are seen on his fingernails and high levels of arsenate are seen in his blood. Which of the following enzymes of glycolysis is inhibited in this male?

Glyceraldehyde 3-phosphate dehydrogenase

A 23-year-old sprinter performs repeated high-intensity sprints. During anaerobic exercise, his skeletal muscles rely heavily on glycolysis, resulting in increased production of lactate. Which organ is primarily responsible for converting this lactate back into glucose to maintain blood glucose during excercise recovery?

Liver

A 62-year-old man with severe COPD is hospitalized with acute hypoxia. Labs show elevated serum lactate levels. Which of the following best explains the biochemical basis of his lactic acidosis?

Increased NADH/NAD+ ratio in cells

A cancer cell line continues high glycolytic activity even in the presence of oxygen. This is known as:

Warburg effect

A 3-day-old newborn is brought to the pediatrician due to worsening lethargy, vomiting, and poor feeding. She is exclusively breast-fed. Examination shows dehydration, hypotonia, and somnolence. Laboratory testing reveals high-anion gap metabolic acidosis, hypoglycemia, and markedly elevated propionate, consistent with an inability to convert propionyl-CoA to methylmalonyl-Co. This defect prevents the infant from using which of the following amino acids for energy production?

Valine

A researcher studies fasting physiology in hepatocytes. She notices that when mitochondrial acetyl-CoA levels rise, the flux of pyruvate into oxaloacetate markedly increases.

Which enzyme is being activated to allow gluconeogenesis to proceed?

Pyruvate carboxylase

Which of the following enzymes is unique to gluconeogenesis and not used in glycolysis?

Fructose 1,6-biphosphate

A 21-year-old man is brought to the emergency department due to confusion. His roommate says that he has been binge drinking for the last 5 days and probably has had very little to eat. The patient's medical history is significant for alcohol-related seizures 1 year ago. He had been sober until 2 weeks ago, when he started drinking again. The patient's past medical history is otherwise unremarkable. On examination, he responds to voice but does not follow commands. Fingerstick glucose is 35 mg/dl and urine is strongly positive for ketones. Suppression of which of the following is the primary cause of this patient’s hypoglycemia?

• A marathon runner becomes hypoglycemic after prolonged fasting. His liver is actively converting alanine from muscle into glucose. Which pathway is being used?

Gluconeogenesis

A 9-month-old infant is brought to the clinic due to poor weight gain, recurrent respiratory infections, and progressive muscle weakness. The mother reports that the child tires easily during feeding and has had episodes of vomiting after meals. Physical examination shows hypotonia, hepatosplenomegaly, and diminished deep-tendon reflexes. Liver biopsy demonstrates long, unbranched glycogen chains with markedly reduced a-1,6 branching points.

Which of the following is the most likely diagnosis?

Andersen disease

A 7-month-old girl is brought in for evaluation of poor growth. Her mother reports frequent feeding but minimal weight gain. The infant has hepatomegaly, truncal hypotonia, and episodes of vomiting, especially, in the morning. Labs show hypoglycemia, ketoacidosis, and liver biopsy reveals fibrosis with cytosolic accumulation of abnormally structured glycogen lacking proper branching. Which enzyme is most likely deficient in this patient?

Glycogen debrancher enzyme

A 6-month-old boy presents with poor feeding. His mother says that he has difficulty holding his head up while breastfeeding and his suckling seems weaker than usual. Weight is at the 5th percentile. Length and head circumference are tracking along the 25th percentile. Physical examination shows hepatomegaly and hypotonia in all 4 limbs. Cardiac auscultation shows a gallop rhythm, and chest x-ray reveals severe cardiomegaly. Muscle biopsy shows enlarged lysosomes containing periodic acid-Schiff (PAS)-positive material. Which of the following enzymes is most likely deficient in this patient?

Acid-alpha glucosidase

A 21-year-old athlete needs rapid post-exercise muscle glycogen replenishment. Insulin surges activate a key enzyme to promote glycogen synthesis.

Which enzyme is directly activated?

Glycogen synthase

The uronic acid pathway (glucose→glucuronic acid) is crucial for which function?

Conjugation of bilirubin and detoxification

The oxidative phase of the pentose phosphate pathway produces:

NADPH

A 22-year-old man develops dark urine, jaundice, and fatigue two days after starting trimethoprim-sulfamethoxazole for a skin infection.

Exam shows scleral icterus. Labs reveal:

• Decreased hemoglobin

• Increased LDH

• Increased indirect bilirubin

• Decreased haptoglobin

Blood smear: bite cells and Heinz bodies. What is the most likely diagnosis?

G6PD deficiency

A patient with Gilbert syndrome is given a medication that is cleared by hepatic glucuronidation.

Which metabolite produced by the uronic acid pathway is directly used in conjugation reactions to enhance excretion?

UDP-glucuronate (UDP-glucoronic acid)

A 6-month-old boy is brought to the emergency department by his mother because of recent onset of vomiting, irritability, and jaundice. The infant was born at term and had been healthy until the onset of these symptoms. All of his vaccinations are up-to-date. He had been breast-fed exclusively until 1 week ago, when cereals and fruit juices were introduced into his diet. Further evaluation reveals hepatomegaly and abnormal liver function tests. Which of the following enzymes is most likely to be deficient in this patient?

Aldolase B

A 25-year-old male, recent immigrant to US who appears healthy, comes to the outpatient for a health check-up. History reveals that as a child he had a ‘problem with a sugar metabolism’. Currently he is not on any dietary restriction and eats plenty of fruits, meat, vegetables, with good quantity of milk. At the outpatient, urine samples repeatedly test positive to reducing sugars but negative to glucose oxidase on urine dipstick. Which of the following enzymes is most likely deficient in this patient?

Fructokinase

An infant, within few days after first intake of milk, presents with severe diarrhea and vomiting. On physical examination, hepatomegaly is seen, cataracts are noted in the eyes of the infant and urine test confirms the diagnosis of the pediatrician. Pediatrician advises immediate withdrawl of lactose from the diet of the infant. Which of the following enzymes is deficient in this infant?

Galactose 1-phosphate uridyl transferase

A 3-year old boy recently died from myocardial infarction. He had a history of intellectual disability. Autopsy reveals cardiomegaly and hepatosplenomegaly as well as diffuse haze over the corneas bilaterally. Which of the following would you expect to accumulate in the coronary arteries?

Dermatan sulfate

A 5-year-old child presents with short stature, skeletal dysplasia, kyphosis, and normal intellect. Corneal clouding is present. GAG analysis shows increased keratan sulfate. Which enzyme deficiency is most consistent?

Galactose-6-sulfatase

A 9-month-old infant presents with recurrent respiratory infections, hernias, and failure to thrive. Physical exam shows macroglossia, large head, and cloudy corneas. Urine test shows elevated dermatan sulfate.

What enzyme deficiency is expected?

Alpha-l-iduronidase

Chronic alcoholism causes fatty liver primarily because increased NADH:

Converts OAA→malate, inhibiting the TCA cycle

A deficiency of delta-6 desaturase leads to decreased synthesis of essential fatty acids. Which clinical presentation is expected?

Scaly dermatitis

A 32-year-old woman presents with 2 months of fatigue, thinning hair, and a scaly rash around her nose and mouth. She recently began a high-protein "fitness" diet that includes daily raw-egg smoothies.

Physical examination shows mild conjunctival pallor, patchy alopecia, and dermatitis over the perioral region. Laboratory studies are normal except for mild metabolic acidosis. Which of the following enzymes requires the vitamin that is deficient in this patient?

Acetyl-CoA carboxylase (Vitamin B7, biotin deficiency)

A 22-year-old woman presents with progressive difficulty walking, night blindness, and dry scaly skin. Exam shows cerebellar ataxia and peripheral neuropathy.

Alpha-oxidation