During high-intensity exercise, which carbohydrate provides immediate energy despite low concentration in blood?
Answer: B
Muscle glycogen is the primary energy source during high-intensity exercise because muscle lacks glucose-6-phosphatase and retains glucose-6-phosphate for glycolysis.
Q.42Medium
Which of the following is NOT a function of glycogen in liver?
Answer: D
Liver glycogen maintains blood glucose but cannot directly supply glucose-6-phosphate to other tissues as glucose-6-phosphate cannot cross cell membranes.
Q.43Medium
A newborn presents with hepatomegaly, lactic acidosis, and hypoglycemia. Enzyme analysis shows deficiency of glucose-6-phosphatase. Which disease is this?
Answer: C
Von Gierke disease (GSD Type I) results from glucose-6-phosphatase deficiency, preventing final step of both gluconeogenesis and glycogenolysis, causing severe hypoglycemia.
Q.44Medium
In hereditary fructose intolerance (HFI), which enzyme deficiency causes accumulation of fructose-1-phosphate?
Answer: B
HFI results from aldolase B deficiency, preventing cleavage of fructose-1-phosphate into DHAP and glyceraldehyde, leading to accumulation and hepatotoxicity.
Q.45Medium
In the pentose phosphate pathway, the oxidative phase generates NADPH. Which metabolic process primarily utilizes this NADPH in fed state?
Answer: C
NADPH from the oxidative pentose phosphate pathway is essential for reductive biosynthesis of fatty acids and cholesterol, which occur predominantly in the fed state.
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Q.46Medium
The Haworth projection of glucose differs from its Fischer projection. Which structural feature is best represented in Haworth projection?
Answer: B
Haworth projection depicts the cyclic hemiacetal structure of glucose in its pyranose form, clearly showing the anomeric carbon and ring geometry.
Q.47Medium
During fasting, which hormonal change directly increases hepatic glycogenolysis?
Answer: B
Glucagon and epinephrine activate phosphorylation cascades that activate glycogen phosphorylase and inactivate glycogen synthase, promoting glycogenolysis.
Q.48Medium
Which adaptation occurs in liver during prolonged fasting to maintain blood glucose?
Answer: B
After 8-12 hours of fasting, hepatic glycogen depletes. The liver then relies on gluconeogenesis from Cori cycle lactate and amino acids to maintain blood glucose.
Q.49Medium
A 45-year-old patient with Type 2 diabetes mellitus shows elevated fasting blood glucose (180 mg/dL) but normal HbA1c levels initially. Which carbohydrate metabolism pathway is primarily impaired in this patient's liver?
Answer: A
Type 2 diabetes shows hepatic insulin resistance leading to impaired glycogenesis (reduced glycogen synthesis) and uncontrolled gluconeogenesis (excessive glucose production). This causes elevated fasting glucose despite normal HbA1c if glycemic control improves later. The liver fails to suppress glucose production in response to insulin.
