next step test

[Pediateix]

Question 39
Ethanol is used as a temporary treatment for poisoning with ethylene glycol (ethane-1,2-diol). The efficacy of alcohol as an antidote is best explained by:

A.
the high affinity of ethanol for ADH and the toxicity of ethylene glycol.

B.
the low affinity of ethanol for ADH and the toxicity of ethylene glycol.

C.
the high affinity of ethanol for ADH and the toxicity of glycolic acid.

D.
the low affinity of ethanol for ADH and the toxicity of glycolic acid.

Your answer was incorrect

38.26% of students answered this question correctly.

56.68%

3.79%

38.26%

1.26%

A B C D
Answer Explanation:

• Difficulty: 3 Hard
• Reasoning Skill: 2 Scientific Reasoning and Problem Solving
• Concept Category: 3B Organ Systems

C is correct. This is a difficult question that asks us to make inferences based on passage information, so breaking it down helps. The question stem doesn’t give us a lot of information, but we should note that ethanol and ethylene glycol are both alcohols, so both can be processed by ADH in the liver. In order for ethanol to act as an antidote, it somehow blocks its toxic effects. If ethanol has a high affinity for ADH, in theory it could prevent the conversion of ethylene glycol to its aldehyde and carboxylic acid. This is exactly what occurs; alcohol’s high affinity for ADH keeps ethylene glycol from being converted to glycolic acid, a toxic metabolite. Ethylene glycol itself is not very toxic.



A, B: Ethylene glycol is not toxic; its metabolites are.

D: Alcohol has a higher affinity for ADH than ethylene glycol.


how do you know ethylene glycol is not toxic

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[wizzed101]

I don't have the passage but B and D can be eliminated outright because the purpose of ADH is to retain water. Detoxification involves making the poison soluble to pass out as urine. Ethanol is said to help so you should infer that it generally has positive effects which include higher urine output.

As for A or C, the passage should contain hints. It's not always the metabolites that are poisonous.

 

[Domepiece]

In this context, ADH is shorthand for alcohol dehydrogenase, not antidiuretic hormone.

Not sure if this is a passage based question or a stand-alone question, but this question can be answered through inference. Ingestion of ethanol would do nothing to directly to eliminate a previously ingested substance as it isn't a chelating agent. Thus, ethelene glycol wouldn't be toxic in and of itself, eliminating A&B. The answer choices make clear that there is a link between ADH function and ethylene glycol's toxicity. Inferring that ADH creates the toxic substance (apparently glycolic acid), a competitive inhibitor would block ethylene glycol from being metabolized. A competitive inhibitor needs a higher affinity than another substrate to function, thus answer D is eliminated and C is correct.

Hope this helps!

Edit: Wrong letters, whoops.

 

[wizzed101]

Ingestion of ethanol would do nothing to directly to eliminate a previously ingested substance as it isn't a chelating agent. Thus, ethelene glycol wouldn't be toxic in and of itself, eliminating B&D.

Please don't do this.