USMLE Questions Flashcards
Hospital testing reveals that the infant can increase her blood glucose after breast feeding but that it is not maintained at normal levels 3-4 hours after feeding. What’s the most likely diagnosis?
a) intestinal malabsorption of lactose
b) galactosemia with inability to convert lactose to glucose
c) fructosemia with inability to liberate sucrose from glucose
d) glycogen storage disease
e) growth hormone deficiency with inability to maintain glucose
Glycogen storage disease
Which glycoside contains fructose and therefore should be avoided when feeding or treating this infant?
a) sucrose
b) oaubain
c) lactose
d) maltose
e) streptomycin
Sucrose
Which of the following carbohydrates would be most abundant in the diet of strict vegetarians?
a) amylase
b) lactose
c) cellulose
d) maltose
e) glycogen
Cellulose
Which of the following results after exercise would support a diagnosis of glycogen storage disease in this teenager?
a) increase oxaloacetate, decreased glucose
b) increased glycerol and glucose
c) increased lactate and glucose
d) increased pyruvate and stable glucose
e) stable lactate and glucose
Increased lactate and glucose
Independent of specific enzyme levels, the availability of what other substance is rate-limiting in the clearance of ethanol?
a) NADH
b) NAD+
c) FADH
d) FAD+
e) NADPH
NAD+
Poorly perfused areas exposed to chronic hypoxia have decreased metabolic energy for tissue maintenance and repair. What is an important reason for this?
a) increase hexokinase activity owing to increased oxidative phosphorylation
b) increased ethanol formation from pyruvate on changing from anaerobic to aerobic metabolism
c) increased glucose utilization via the pentose phosphate pathway on changing from anaerobic metabolism
d) decreased ATP generation and increased glucose utilization on changing from aerobic to anaerobic metabolism
e) decreased respiratory quotient on changing from carbohydrate to fat as the major metabolic fuel
Decreased ATP generation and increased glucose utilization on changing from aerobic to anaerobic metabolism
Following a fad diet meal of skim milk and yogurt, patient experiences abdominal distention, nausea, cramping, and pain followed by watery diarrhea. This set of symptoms is observed each time the meal is consumed. What is the most likely diagnosis?
a) steatorrhea
b) lactase deficiency
c) maltose deficiency
d) sialidase deficiency
e) lipoprotein lipase deficiency
Lactase deficiency
Genetic variation in an enzyme that metabolizes the liver metabolite of alcohol, which is which of the following?
a) methanol
b) acetone
c) acetylaldehyde
d) hydrogen peroxide
e) glycerol
Acetaldehyde
Glycogen storage disease exhibits symptoms due to altered liver or muscle metabolism. Which conversions explains the difference in these presentations?
a) conversion of glycogen to lactate in liver
b) conversion of glycogen and lactase to glucose in liver
c) conversion of glycogen to glucose in muscle
d) conversion of glycogen to alanine in muscle
e) conversion of glycogen to glucose-6-phosphate in liver
Conversion of glycogen and lactate to glucose in liver
The child’s anemia is explained by the fact that ATP is produced by which of the following pathways?
a) glycogen breakdown
b) glycolysis
c) oxidative phosphorylation
d) pentose phosphate cycle
e) lactate conversion to glucose (Cori cycle)
Glycolysis
The physician suspects G6PD deficiency, implying defective synthesis of which of the following compounds?
a) deoxyribose and NADP
b) glucose and lactate
c) lactose and NADPH
d) Ribose and NADPH
e) sucrose and NAD
Ribose and NADPH
A blood screen for galactosemia is positive, and lactose-containing substances are removed from the diet. Lactose is toxic in this case because of what?
a) excess glucose accumulates in the blood
b) galactose is converted to the toxic substance galacitol (dulcitol)
c) galactose competes for glucose during hepatic glycogen synthesis
d) galactose is itself toxic in even small amounts
e) glucose metabolism is shut down by excess galactose
Galactose is converted to the toxic substance galacitol (dulcitol)
Which of the following best explains why fructose is often used as a carbohydrate substitute in special foods for patients with diabetes mellitus?
a) fructose is a better substrate for hexokinase
b) fructose stimulates residual insulin release
c) fructose has a specific kinase in liver that allows bypass of phosphofructokinase
d) fructose is phosphorylated and cleaned to triose phosphates, which cannot be used for gluconeogenesis
e) hexokinase phosphorylates fructose in extra hepatic tissues, and its activist will not be affected by high glucose concentrations in diabetes
Fructose has a specific kinase in liver the allows bypass of phosphofructokinase
Her physician suspects hereditary fructose intolerance, which is a deficiency of the enzyme aldolase B. The symptoms and serum abnormalities of this disease are due to what?
a) accumulation of hexose phosphates, phosphate and ATP depletion, defective electron transport, and glycogen phosphorylase inhibition
b) accumulation of triose phosphates, phosphate and ATP excess, defective glycolysis, and glycogen synthase inhibition
c) accumulation of triose phosphates, phosphate and ATP depletion, defective electron transport, and glycogen synthase inhibition
d) accumulation of hexose phosphates, phosphate and ATP depletion, defective electron transport, and glycogen phosphorylate stimulation
e) accumulation of hexose phosphates, phosphate and ATP excess, defective electron transport, and glycogen phosphorylase stimulation
Accumulation of hexose phosphates, phosphate and ATP depletion, defective electron transport, and glycogen phosphorylase inhibition.
Assay of usual glycogen enzyme deficiencies in the liver specimen is normal, so the metabolic consultant recommends assay of rarer enzyme deficiencies that influence glycogen metabolism. These enzymes would most likely include?
a) hexokinase
b) cAMP-dependent protein kinase
c) G6PD
d) phosphofructokinase
e) fructose-1,6-diphophatase
cAMP-dependent protein kinase
The parents have immigrated from Russia and report that the child’s older brother was diagnosed with a “deb rancher” enzyme deficiency with similar glycogen storage. This diagnosis would imply accumulation of glycogen with which type of glucose linkages?
a) linear alpha-1 → 4 linkages with branching alpha-1 → 6 linkages
b) linear alpha-1 → 6 linkages with branching beta-1 → 4 linkages
c) linear beta-1 → 4 linkages only
d) linear beta-1 → 6 linkages only
e) branching beta-1 → 6 linkages only
Linear alpha-1 → 4 linkages with branching alpha-1 → 6 linkages
Further analysis of the urine reveals a small amount of fructose and a large amount of an unidentified pentose that is most likely which of the following?
a) galactose
b) glucose
c) lactose
d) mannose
e) xylulose
Lactose
