CASE FILES: BIOCHEMISTRY
C O M P R E H E N SIO N Q U E ST IO N S
[24.1] A 22-year-old soldier collapses from dehydration during maneuvers in
the desert and is sent to a military hospital. Prior to enlisting, a physi-
cian observed a high level of glucose in his urine during an examina-
tion. At first, he was not allowed to enlist because he was suspected of
being a diabetic. Further tests, however, determined that his insulin
level was normal. A glucose tolerance test exhibited a normal pattern.
Laboratory tests following his dehydration episode repeat the previous
findings, but further testing of the urine reveals that only
elevated. Other sugars were not elevated.
This patient’s elevated urinary glucose and his dehydration episode are
caused by a deficiency in which of the following?
A. GLUT 2
B. GLUT 4
C. Insulin receptor
[24.2] Your patient is a 7-month-old baby girl, the second child born to unre-
lated parents. She did not respond well to breast-feeding and was
changed entirely to a formula based on cow’s milk at 4 weeks.
Between 7 and 12 weeks of age, she was admitted to the hospital twice
with a history of screaming after feeding, but was discharged after
observation without a specific diagnosis. Elimination of cow’s milk
from her diet did not relieve her symptoms; her mother reported that
the screaming bouts were worse after the child drank juice and that she
frequently had gas and a distended abdomen. Analysis of a liver nee-
dle biopsy did not reveal any liver enzyme deficiencies. Overall, the
girl is thriving (weight greater than 97th percentile) with no abnormal
findings on physical examination.
If a biopsy of intestinal tissue were obtained from your patient and ana-
lyzed, which of the following would most likely be deficient or
A. GLUT 2
B. GLUT 5