SPOILER AAMC Qbank Bio Vol 1, #55

[iMaree]

Ok so with this question, I knew that NO is a relaxer since the passage says and that L-NMMA is an inhibitor of NO synthase. However, when going through the answer choices, I did not want to make the direct assumption that the absence of NO due to L-NMMA directly leads to constriction of the blood vessels. Therefore if NO isn't present; this would allow acetylcholine to affect the blood vessel without having to compete with NO. I don't know, I just feel like they are a lot of questions on the MCAT where you get screwed because you erroneously made an assumption that you think is trivial.

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[pretty_positron]

First off, eliminate A and D as they have nothing to do with this.

Now you know that NO causes the vasodilation, and the enzyme that synthesizes NO is being inhibited, therefore there is not going to be any vasodilation.

Your question of "Does no vasodilation mean vasoconstriction" is a good one. Note that this is happening to a "relaxing" blood vessel. So that is why the answer choice says "cause the ring to contract" rather than "vasoconstrict" - this means that as opposed to vasodilation, it is just tightening back to normal.

 

[siliso]

You have done overthunk your way out of a correct answer that you knew. The question is assessing whether you know what a competitive inhibitor is and how it works. Remember these qs are pitched to undergrads with a general science background and not to experts at the bleeding edge of research.