TPR Online Test2 Bio Section Question

[tuhtles]

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So in one of the TPR practice tests I just took had a bio section about an experiment testing the effects of injecting a substance called Stilbestrol that produces estrogen-like effects into birds.

One line in the passage stated the following: " Stilbestrol is a crystalline non-steroid with estrogenic effects often superior to those of the estrogen, estradiol."

After reading that line, I interpreted that because Stilbestrol is a non steroid hormone, then it must be a peptide hormone and will bind to cell surface receptors to initiate some cellular changes such as turning on enzymes etc instead of binding to nuclear receptors and triggering transcription.

The following were some of the questions that went with this passage:

If radiolabeled stilbestrol were administered to the experimental chicks, stilbestrol would be found most heavily concentrated:

A. at the cell membrane of oviduct tissue.
B. in the cytoplasm of oviduct tissue.
C. in the nuclei of oviduct tissue.
D. in the mitochondria of oviduct tissue.

Answer was C
I put A, thinking that Stilbestrol was a peptide hormone. Maybe I'm misunderstanding, but how would a non steroid hormone be localized in the nuclei/bind to nuclear receptors....

EDIT: after googling the structure of Stilbestrol, it becomes evident that it could diffuse into the cell.. but i guess i don't get what is the relevance of the word "nonsteroid" in the passage.. seems to have thrown me off..

Anyone have any thoughts on this? Thanks!

Also, could someone clarify this.. only steroid hormones produce changes such as increase in protein synthesis via transcribing more mRNAs? Or can peptide hormones do some intracellular changes that also increases protein synthesis?

 

[POA AFLAT POG]

The non-steroid part seems to be there to throw you off. However, it later says that Stilbestrol has estrogen like effects, if not superior. This tells us that the hormone would have to at least use the same transduction effects as estradiol, meaning that it must have some lipid soluble property.

I agree though, tricky question :\

 

[Synapsis]

I just took this test this morning, and put the same answer you put for this question. In my opinion, this question is silly. Most of the lipid soluble hormones that we're required to know are steroid hormones, excluding the thyroid hormones, which are tyrosine derivatives. Because the passage states that it's a non-steroid, and nothing is given to imply that it's a lipid-soluble tyrosine derivative, I felt forced to conclude that it was water soluble and acting at the membrane.

To answer your second question, peptide hormones can also stimulate transcription, but usually through some other pathway, and often without entering the cell.

 

[tuhtles]

Thanks for the replies! It makes more sense now but ehhh didn't like that question haha
I guess the key thing you had to make a connection was that it has estrogen like effects.

 

[sshah92]

Thanks for the replies! It makes more sense now but ehhh didn't like that question haha
I guess the key thing you had to make a connection was that it has estrogen like effects.

Alright... this is just a silly question. To answer your question, yeah, peptide hormones can through a second messaging system alter transcription of certain proteins. The non-steroid description threw me completely off... I studied this all year and have never heard of any non-steroid hormones (apart from tyrosine derivatives) diffusing through the lipid membrane.

And there ARE examples of hormones that have similar effects but function through different mechanisms. Both aldosterone, a steroid hormone, and vasopressin, a peptide hormone, will increase blood pressure, for example. Just because two hormones have the same "effect" doesn't mean they operate via the same pathway, especially if one is steroid and the other isn't.

Is there something in the passage about it being a tryptophan or tyrosine derivative? I guess that would be a clue that it's lipid-soluble I guess...