Support Group for MCAT

[showeeeeeeeee]

Hey,
I've been doing the aamc practice items and other practic questions and have come across some questions that I got wrong, but I don't know why. It's so frustrating!!!

They don't have an explanation for the answers and I still didn't understand after rereading and trying to look stuff up in texts. I'm wondering if anyone here who has done/is doing these and other practice tests would be interested in using each other for questions/explanations?

My question for now:
In the AAMC biological sciences practice items question number 134!!! I think my problem is I don't understand the question. It would be a little involved to write out the question as it is based on a passage. Please help!!!

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[showeeeeeeeee]

anyone, anyone?

Tweetie?

 

[Jameson]

I think before we can answer your Q we need to know what aamc practice test your are refering to. Is it I,II,III,IV,V? If it's from IV or V I can help you out....

 

[showeeeeeeeee]

Thanks Newton. Actually, I'm working on the practice items, not any of the practice tests quite yet. They come with about 200 questions each for physical sciences and biological.

I may holler when I get into those practice tests!!!

Thanks!

 

[Street Philosopher]

i would try to help you out but I don't have that set of questions...

 

[Mr.D]

showee,

Here's the question

134: Smaller molecules, such as steroids and prostaglandins, that normally do not stimulate
antibody production can be quantified by an RIA. This is most likely because during the assay, the assay molecules can be:

Now, keep in mind that an RIA assay is a very tight assay in which an antibody binds tightly and specifically to an antigen (hormone or a drug according to the passage). Now, in the question it specifically says that steroids and prostaglandins DON'T NORMALLY elicit such a reaction. Keep in mind that we're talking about a specific reaction, so no matter how much
we have of it in solution, it will not bind and therefore not be detected by RIA. Therefore C and D can be eliminated. Now, we have A and B left. One of the cardinal rules about the MCAT is knowing how to ELIMINATE probable answers -
we've know eliminated 50% of our choices. Now the choice is simple - the presence of radioactivity in it of itself cannot stimulate antibody production, if it did, then the entire assay would not work because the then you'd always get a positive response (or a high background to say the least) which would defeat the purpose of the assay. The correct answer is
A - which not only is correct by default, but also because in fact smaller molecules (such as steroids and prostaglandins among others) can in fact elicit a reponse if attached to other macromolecules. The small molecule is termed the
hapten and the large molecule is called the carrier. See Stryer, Biochemistry 4th ed., pg 362 for further details.

 

[showeeeeeeeee]

thanks so much for the reply! I meant to thank you all sooner. I don't know why sometimes it just doesn't make sense until someone else points out what's going on.

:wink: