Proenzymes: digestive protease activation: 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 · Proenzymes: digestive protease activation

Sample item

Duodenal fluid from an infant with protein malabsorption and oedema has very low trypsin and chymotrypsin activity. Adding enteropeptidase restores activity. Which statement describes the normal role of this enzyme?

AIt converts procarboxypeptidase to trypsin directlyBIt activates pepsinogen in the stomachCIt cleaves trypsinogen to trypsin, which then activates the other pancreatic zymogensDIt cleaves dietary lactose at the brush border

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

The answer and the reasoning

C. It cleaves trypsinogen to trypsin, which then activates the other pancreatic zymogens

Enteropeptidase (enterokinase) is a brush border enzyme of the duodenum that removes an N-terminal activation peptide from trypsinogen. Trypsin then activates chymotrypsinogen, proelastase, procarboxypeptidases and more trypsinogen. Congenital deficiency causes diarrhoea, failure to thrive and hypoproteinaemia.

Option by option

A. It converts procarboxypeptidase to trypsin directly
Procarboxypeptidase is activated by trypsin, and enteropeptidase does not form trypsin from it.
B. It activates pepsinogen in the stomach
Pepsinogen is activated by gastric acid and by pepsin itself.
C. It cleaves trypsinogen to trypsin, which then activates the other pancreatic zymogens (correct)
Correct. Enteropeptidase starts the zymogen cascade by generating trypsin.
D. It cleaves dietary lactose at the brush border
Lactose is cleaved by lactase, not by enteropeptidase.

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 C, It cleaves trypsinogen to trypsin, which then activates the other pancreatic zymogens. Enteropeptidase (enterokinase) is a brush border enzyme of the duodenum that removes an N-terminal activation peptide from trypsinogen.

Why is "It converts procarboxypeptidase to trypsin directly" not the answer?

Procarboxypeptidase is activated by trypsin, and enteropeptidase does not form trypsin from it.

Why is "It activates pepsinogen in the stomach" not the answer?

Pepsinogen is activated by gastric acid and by pepsin itself.

Why is "It cleaves dietary lactose at the brush border" not the answer?

Lactose is cleaved by lactase, not by enteropeptidase.

What concept does this question test?

It tests Proenzymes: digestive protease activation in Biochemistry. Trypsin then activates chymotrypsinogen, proelastase, procarboxypeptidases and more trypsinogen. Congenital deficiency causes diarrhoea, failure to thrive and hypoproteinaemia.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Proenzymes: digestive protease activation?

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.