RQ2. JS was prescribed calcium supplements because chronic acidosis can cause bone demineralization, resulting in osteopenia. Vitamin D (1,25-diOH-D3) was also prescribed because vitamin D:
A. binds Gq protein–coupled membrane receptors and causes a rise in inositol trisphosphate with release of calcium from intracellular stores.
B. cannot be synthesized by humans and, therefore, must be supplied in the diet.
C. is a fat-soluble vitamin that increases intestinal absorption of calcium.
D. is the coenzyme-prosthetic group for calbindin, a calcium transporter in the intestine.
RQ3. The hepatomegaly and renomegaly seen in JS are primarily the result of an increase in the amount of glycogen stored in these organs. What is the basis for glycogen accumulation in these organs?
A. Glycolysis is downregulated, which pushes glucose to glycogenesis.
B. Increased oxidation of fatty acids spares glucose for glycogenesis.
C. Glucose 6-phosphate is an allosteric activator of glycogen synthase b.
D. The rise in the insulin/glucagon ratio favors glycogenesis.
RQ4. Glucose 6-phosphatase is an integral protein of the ER membrane. Which of the following statements about such proteins is correct?
A. If glycosylated, the carbohydrate is on the portion of the protein that extends into the cytosol.
B. They are synthesized on ribosomes that are free in the cytosol.
C. The membrane-spanning domain consists of hydrophilic amino acids.
D. The initial targeting signal is an amino terminal hydrophobic signal sequence.
TQ1. What is the likely reason for JS’s twitching movements? TQ2. Why was the liver homogenate treated with detergent? Hint: Think about where the enzyme is located. TQ3. Why is JS’s blood glucose level unaffected by glucagon? Hint: What is the role of glucagon in normal individuals who experience a drop in blood glucose?
TQ4. Why are urate and lactate elevated in a disorder of glycogen metabolism? Hint: It is the result of a decrease in inorganic phosphate (Pi), but why is Pi decreased?
TQ5. A.Why are triacylglycerols and cholesterol elevated? Hint: Glucose is the primary carbon source for their synthesis. B.Why are ketone bodies not elevated?
Case 3: Hyperglycemia and Hyperketonemia
Patient Presentation: MW, a 40-year-old woman, was brought to the hospital in a disoriented, confused state by her husband.
Focused History: As noted on her medical alert bracelet, MW has had type 1 diabetes (T1D) for the last 24 years. Her husband reports that this is her first medical emergency in 2 years.
Physical Examination (Pertinent Findings): MW displayed signs of dehydration (such as dry mucous membranes and skin, poor skin turgor, and low blood pressure) and acidosis (such as deep, rapid breathing [Kussmaul respiration]). Her breath had a faintly fruity odor. Her temperature was normal.
Pertinent Test Results: Rapid, bedside tests were strongly positive for glucose and acetoacetate and negative for protein. Results on blood tests performed by the clinical laboratory are shown below:
H=High;L=Low.
Microscopic examination of her urine revealed a urinary tract infection (UTI).
Diagnosis: MW is in diabetic ketoacidosis (DKA) that was precipitated by a UTI. [Note: Diabetes increases the risk for infections such as UTI.]