Which enzyme deficiency causes Pompe disease (GSD Type II)?
Answer: B
Pompe disease results from deficiency of acid α-glucosidase (lysosomal α-1,4-glucosidase), leading to accumulation of glycogen in lysosomes, especially in muscles and heart.
Q.82Medium
During the pentose phosphate pathway, which coenzyme is reduced to generate NADPH?
Answer: C
NADP+ is reduced to NADPH in the oxidative phase of the pentose phosphate pathway, primarily in the G6PD and 6-PGD reactions.
Q.83Medium
Which of the following best explains why glycogen is more soluble than starch despite similar glycosidic linkages?
Answer: A
Glycogen has more frequent α-1,6 branch points (approximately every 8-12 glucose units) compared to starch, increasing its solubility and accessibility for enzyme action.
Q.84Medium
In a patient with von Gierke disease, excessive hepatic glucose production is primarily due to:
Answer: C
Von Gierke disease (GSD Type I) involves glucose-6-phosphatase deficiency, leading to impaired glucose release. However, alternative glucose production through gluconeogenesis and pentose phosphate pathway increases.
Q.85Medium
Which of the following substrates can be directly utilized for glycogen synthesis in the liver?
Answer: B
Glucose-1-phosphate is converted to UDP-glucose by UDP-glucose pyrophosphorylase, which is the activated form used by glycogen synthase for glycogen synthesis.
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Q.86Medium
A patient presents with inability to metabolize galactose. Which enzyme deficiency is most likely responsible for classical galactosemia?
Answer: B
Classical galactosemia results from galactose-1-phosphate uridyltransferase (GALT) deficiency, causing accumulation of galactose-1-phosphate and galactosylated proteins.
Q.87Medium
The branching enzyme in glycogen synthesis catalyzes which type of reaction?
Answer: B
Branching enzyme (amylo-1,6-transglucosidase) transfers segments of α-1,4-linked glucose chains to create α-1,6 branch points in glycogen.
Q.88Medium
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.89Medium
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.90Medium
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.91Medium
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.92Medium
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.
Q.93Medium
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.94Medium
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.95Medium
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.96Medium
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.
Q.97Medium
In the context of lipid metabolism, what does beta-oxidation primarily accomplish?
Answer: B
Beta-oxidation is the catabolic pathway that breaks down fatty acids in the mitochondria, producing acetyl-CoA which enters the Krebs cycle for ATP production.
Q.98Medium
Which of the following is a consequence of excessive cholesterol accumulation in arteries?
Answer: B
High cholesterol, particularly LDL cholesterol, can accumulate in artery walls forming atherosclerotic plaques, leading to arterial narrowing (atherosclerosis) and increased risk of heart disease.
Q.99Medium
A patient with familial hypercholesterolemia shows extremely high cholesterol levels. What is the most likely defect?
Answer: B
Familial hypercholesterolemia is caused by mutations in the LDL receptor gene, preventing cells from taking up LDL particles, resulting in elevated blood cholesterol levels.
Q.100Medium
Which enzyme catalyzes the rate-limiting step of cholesterol synthesis?
Answer: B
HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonate, the rate-limiting and key regulatory step in cholesterol biosynthesis. It is targeted by statin drugs.
