Culture methods: anaerobic jar: practice question

A Microbiology 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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Microbiology · Culture methods: anaerobic jar

Sample item

In a GasPak anaerobic jar, hydrogen-generating sachets and a catalyst are used. How does the catalyst create anaerobic conditions inside the sealed jar?

AIt absorbs oxygen by oxidising alkaline pyrogallolBPalladium catalyses the combination of hydrogen with residual oxygen to form waterCIt replaces air with nitrogen by displacementDIt lowers the redox potential by adding thioglycollate

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

The answer and the reasoning

B. Palladium catalyses the combination of hydrogen with residual oxygen to form water

In the jar, hydrogen released from the sachet combines with oxygen on a palladium catalyst, forming water and removing oxygen. Methylene blue indicator strips turn colourless when conditions are truly anaerobic. A poisoned or wet catalyst is a common cause of failure.

Option by option

A. It absorbs oxygen by oxidising alkaline pyrogallol
Alkaline pyrogallol is a different chemical method that absorbs oxygen and is not used in a catalyst-based jar.
B. Palladium catalyses the combination of hydrogen with residual oxygen to form water (correct)
Correct. Palladium-catalysed formation of water removes the oxygen.
C. It replaces air with nitrogen by displacement
Gas flushing with nitrogen is a separate technique and is not how a catalyst works.
D. It lowers the redox potential by adding thioglycollate
Thioglycollate is a reducing agent in broth media, not a jar catalyst.

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 Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Palladium catalyses the combination of hydrogen with residual oxygen to form water. In the jar, hydrogen released from the sachet combines with oxygen on a palladium catalyst, forming water and removing oxygen.

Why is "It absorbs oxygen by oxidising alkaline pyrogallol" not the answer?

Alkaline pyrogallol is a different chemical method that absorbs oxygen and is not used in a catalyst-based jar.

Why is "It replaces air with nitrogen by displacement" not the answer?

Gas flushing with nitrogen is a separate technique and is not how a catalyst works.

Why is "It lowers the redox potential by adding thioglycollate" not the answer?

Thioglycollate is a reducing agent in broth media, not a jar catalyst.

What concept does this question test?

It tests Culture methods: anaerobic jar in Microbiology. Methylene blue indicator strips turn colourless when conditions are truly anaerobic. A poisoned or wet catalyst is a common cause of failure.

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 Culture methods: anaerobic jar?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology 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.