Carbohydrate metabolism: GLUT2 defect in Fanconi-Bickel syndrome: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Carbohydrate metabolism: GLUT2 defect in Fanconi-Bickel syndrome

Sample item

An infant has failure to thrive, hepatomegaly, rickets and proximal renal tubular dysfunction with glycosuria, phosphaturia and aminoaciduria. There is fasting hypoglycaemia, postprandial hyperglycaemia and glycogen accumulation in the liver. Which transporter is defective?

AGLUT1BGLUT2CGLUT4DSGLT1

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. GLUT2

GLUT2 is a high-capacity bidirectional transporter in hepatocytes, pancreatic beta cells, the basolateral membrane of enterocytes and proximal tubular cells. Its failure in Fanconi-Bickel syndrome traps glucose in the liver and kidney, giving glycogen accumulation, tubular dysfunction and impaired glucose homeostasis. It is inherited as an autosomal recessive disorder.

Option by option

A. GLUT1
GLUT1 deficiency affects brain glucose transport and causes seizures with low CSF glucose.
B. GLUT2 (correct)
Correct. GLUT2 loss traps glucose in liver and tubular cells and affects absorptive and sensing tissues.
C. GLUT4
GLUT4 is insulin-dependent and found in muscle and adipose tissue, not in liver or renal tubules.
D. SGLT1
SGLT1 defects cause glucose-galactose malabsorption with watery diarrhoea.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, GLUT2. GLUT2 is a high-capacity bidirectional transporter in hepatocytes, pancreatic beta cells, the basolateral membrane of enterocytes and proximal tubular cells.

Why is "GLUT1" not the answer?

GLUT1 deficiency affects brain glucose transport and causes seizures with low CSF glucose.

Why is "GLUT4" not the answer?

GLUT4 is insulin-dependent and found in muscle and adipose tissue, not in liver or renal tubules.

Why is "SGLT1" not the answer?

SGLT1 defects cause glucose-galactose malabsorption with watery diarrhoea.

What concept does this question test?

It tests Carbohydrate metabolism: GLUT2 defect in Fanconi-Bickel syndrome in Biochemistry. Its failure in Fanconi-Bickel syndrome traps glucose in the liver and kidney, giving glycogen accumulation, tubular dysfunction and impaired glucose homeostasis. It is inherited as an autosomal recessive disorder.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Carbohydrate metabolism: GLUT2 defect in Fanconi-Bickel syndrome?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.