Home Subjects Biochemistry

Biochemistry

Metabolic pathways, enzymes, proteins

278 Q 3 Topics Take Test
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Difficulty: All Easy Medium Hard 91–100 of 278
Topics in Biochemistry
All Proteins & Enzymes 100 Carbohydrates 100 Lipids 78
Q.91 Medium Carbohydrates
In hereditary fructose intolerance (HFI), which enzyme deficiency causes accumulation of fructose-1-phosphate?
A Fructokinase
B Aldolase B
C Fructose-1,6-bisphosphatase
D Fructose-1-phosphatase
Correct Answer:  B. Aldolase B
EXPLANATION

HFI results from aldolase B deficiency, preventing cleavage of fructose-1-phosphate into DHAP and glyceraldehyde, leading to accumulation and hepatotoxicity.

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Q.92 Medium Carbohydrates
A newborn presents with hepatomegaly, lactic acidosis, and hypoglycemia. Enzyme analysis shows deficiency of glucose-6-phosphatase. Which disease is this?
A McArdle disease
B Pompe disease
C Von Gierke disease
D Cori disease
Correct Answer:  C. Von Gierke disease
EXPLANATION

Von Gierke disease (GSD Type I) results from glucose-6-phosphatase deficiency, preventing final step of both gluconeogenesis and glycogenolysis, causing severe hypoglycemia.

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Q.93 Medium Carbohydrates
Which of the following is NOT a function of glycogen in liver?
A Maintaining blood glucose levels between meals
B Providing structural support to hepatocytes
C Acting as glucose buffer during fasting
D Supplying glucose-6-phosphate to extrahepatic tissues
Correct Answer:  D. Supplying glucose-6-phosphate to extrahepatic tissues
EXPLANATION

Liver glycogen maintains blood glucose but cannot directly supply glucose-6-phosphate to other tissues as glucose-6-phosphate cannot cross cell membranes.

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Q.94 Medium Carbohydrates
During high-intensity exercise, which carbohydrate provides immediate energy despite low concentration in blood?
A Blood glucose from liver glycogenolysis
B Muscle glycogen
C Circulating fructose
D Dietary disaccharides
Correct Answer:  B. Muscle glycogen
EXPLANATION

Muscle glycogen is the primary energy source during high-intensity exercise because muscle lacks glucose-6-phosphatase and retains glucose-6-phosphate for glycolysis.

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Q.95 Medium Carbohydrates
The branching enzyme in glycogen synthesis catalyzes which type of reaction?
A Removal of α-1,4-glucose units
B Transfer of α-1,4-glucose chain segment to α-1,6 position
C Addition of glucose to growing chain via α-1,4 bond
D Phosphorylation of glucose-6-phosphate
Correct Answer:  B. Transfer of α-1,4-glucose chain segment to α-1,6 position
EXPLANATION

Branching enzyme (amylo-1,6-transglucosidase) transfers segments of α-1,4-linked glucose chains to create α-1,6 branch points in glycogen.

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Q.96 Medium Carbohydrates
A patient presents with inability to metabolize galactose. Which enzyme deficiency is most likely responsible for classical galactosemia?
A Galactokinase deficiency
B Galactose-1-phosphate uridyltransferase deficiency
C UDP-galactose epimerase deficiency
D Lactase deficiency
Correct Answer:  B. Galactose-1-phosphate uridyltransferase deficiency
EXPLANATION

Classical galactosemia results from galactose-1-phosphate uridyltransferase (GALT) deficiency, causing accumulation of galactose-1-phosphate and galactosylated proteins.

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Q.97 Easy Carbohydrates
Which enzyme catalyzes the reversible conversion of glucose-6-phosphate to fructose-6-phosphate?
A Phosphofructokinase
B Phosphoglucose isomerase
C Hexokinase
D Aldolase
Correct Answer:  B. Phosphoglucose isomerase
EXPLANATION

Phosphoglucose isomerase catalyzes the interconversion of glucose-6-phosphate and fructose-6-phosphate in glycolysis.

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Q.98 Easy Carbohydrates
The disaccharide formed by α-glucose and β-fructose joined by α-1,2-glycosidic bond is:
A Lactose
B Maltose
C Sucrose
D Trehalose
Correct Answer:  C. Sucrose
EXPLANATION

Sucrose is composed of glucose and fructose linked by α-1,2-glycosidic bond. Maltose has α-1,4 bond between two glucose molecules.

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Q.99 Easy Carbohydrates
Which of the following carbohydrates is a ketohexose?
A Fructose
B Glucose
C Galactose
D Ribose
Correct Answer:  A. Fructose
EXPLANATION

Fructose is a ketohexose (6-carbon ketone sugar), while glucose, galactose are aldohexoses, and ribose is a pentose.

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Q.100 Hard Carbohydrates
Which statement accurately describes the relationship between blood glucose regulation and the Warburg effect in cancer cells?
A Both involve increased oxidative phosphorylation
B Warburg effect reduces glucose utilization, allowing more glucose for normal tissues
C Cancer cells utilize lactate as primary fuel, reducing blood glucose consumption
D Warburg effect causes high glucose consumption and lactate production despite oxygen availability
Correct Answer:  D. Warburg effect causes high glucose consumption and lactate production despite oxygen availability
EXPLANATION

The Warburg effect describes the metabolic shift in cancer cells toward anaerobic glycolysis, producing lactate even in the presence of oxygen, resulting in high glucose consumption.

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