General microbiology and sterilisation: why moist heat is more effective: 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 · General microbiology and sterilisation: why moist heat is more effective

Sample item

At the same temperature, moist heat kills organisms in much less time than dry heat. Which statement best explains this?

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

The answer and the reasoning

C. Steam condenses on the article and releases latent heat while denaturing proteins

Moist heat coagulates and denatures proteins at lower temperatures than dry heat, which acts mainly by oxidation. Steam also gives up latent heat as it condenses, rapidly heating the load. Alkylation is the mechanism of ethylene oxide, and pyrimidine dimers arise from ultraviolet radiation.

Option by option

  • A. Steam produces pyrimidine dimers in the genome

    Pyrimidine dimers are produced by ultraviolet radiation.

  • B. Steam alkylates the nucleic acids of the organism

    Alkylation of nucleic acids is characteristic of ethylene oxide and formaldehyde, not steam.

  • C. Steam condenses on the article and releases latent heat while denaturing proteins (correct)

    Correct. Latent heat release and protein coagulation make moist heat efficient.

  • D. Steam dissolves the lipid bilayer without affecting proteins

    Steam acts mainly on proteins by coagulation, not by selectively dissolving membranes.

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.

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Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Steam condenses on the article and releases latent heat while denaturing proteins. Moist heat coagulates and denatures proteins at lower temperatures than dry heat, which acts mainly by oxidation.

Why is "Steam produces pyrimidine dimers in the genome" not the answer?

Pyrimidine dimers are produced by ultraviolet radiation.

Why is "Steam alkylates the nucleic acids of the organism" not the answer?

Alkylation of nucleic acids is characteristic of ethylene oxide and formaldehyde, not steam.

Why is "Steam dissolves the lipid bilayer without affecting proteins" not the answer?

Steam acts mainly on proteins by coagulation, not by selectively dissolving membranes.

What concept does this question test?

It tests General microbiology and sterilisation: why moist heat is more effective in Microbiology. Steam also gives up latent heat as it condenses, rapidly heating the load. Alkylation is the mechanism of ethylene oxide, and pyrimidine dimers arise from ultraviolet radiation.

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 General microbiology and sterilisation: why moist heat is more effective?

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.