AAMC Section Bank Bio Qn 51

[bellowbruins]

Hello,
I want to clear up some misunderstanding from this problem. The question is as follows:

Which statement describes a characteristics of FSH?

A. FSH DOES NOT REQUIRE TRANSPORT PROTEINS TO REMAIN SOLUBLE IN THE BLOODSTREAM.
B. FSH ENTERS THE BLOODSTREAM BY DIFFUSING ACROSS THE PLASMA MEMBRANE OF ENDOCRINE CELLS.
C. FSH IS SYNTHESIZED FROM CHOLESTEROL.
D. FSH IS DERIVED FROM SINGLE AMINO ACID.

AAMC solution states A because FSH is peptide hormone and thus, they are hydrophilic, and does not require transport proteins to remain soluble in bloodstream. While on the other hand, steroid needs transport proteins to remain soluble in bloodstream. So, i was thinking shouldn't FSH need like transport proteins or something to be carried across the plasma membrane and enters bloodstream since they are hydrophilic and cannot diffuse across the membrane? Isn't it contradicting with AAMC answer of A saying they do not need transport protein? Or they are just completely two different things? Please help me clear my misunderstandings.

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[tj123]

Hello,
I want to clear up some misunderstanding from this problem. The question is as follows:

Which statement describes a characteristics of FSH?

A. FSH DOES NOT REQUIRE TRANSPORT PROTEINS TO REMAIN SOLUBLE IN THE BLOODSTREAM.
B. FSH ENTERS THE BLOODSTREAM BY DIFFUSING ACROSS THE PLASMA MEMBRANE OF ENDOCRINE CELLS.
C. FSH IS SYNTHESIZED FROM CHOLESTEROL.
D. FSH IS DERIVED FROM SINGLE AMINO ACID.

AAMC solution states A because FSH is peptide hormone and thus, they are hydrophilic, and does not require transport proteins to remain soluble in bloodstream. While on the other hand, steroid needs transport proteins to remain soluble in bloodstream. So, i was thinking shouldn't FSH need like transport proteins or something to be carried across the plasma membrane and enters bloodstream since they are hydrophilic and cannot diffuse across the membrane? Isn't it contradicting with AAMC answer of A saying they do not need transport protein? Or they are just completely two different things? Please help me clear my misunderstandings.

Small, unpolar (hydrophobic) molecules diffuse across the plasma membrane most easily. This is also true for steroid hormones because they are hydrophobic so they diffuse through the plasma membrane and bind to a receptor in the nucleus or cytosol. FSH is a peptide derivitive, which means that it cannot diffuse through the membrane and it needs some kind of protien to aid it. This question is basically about whether FSH is hydrophobic or hydrophilic. Hydrophilic molecules cannon diffuse through a membrane.

 

[aldol16]

AAMC solution states A because FSH is peptide hormone and thus, they are hydrophilic, and does not require transport proteins to remain soluble in bloodstream. While on the other hand, steroid needs transport proteins to remain soluble in bloodstream. So, i was thinking shouldn't FSH need like transport proteins or something to be carried across the plasma membrane and enters bloodstream since they are hydrophilic and cannot diffuse across the membrane? Isn't it contradicting with AAMC answer of A saying they do not need transport protein? Or they are just completely two different things? Please help me clear my misunderstandings.

The question never makes a statement about whether FSH needs assistance to cross the plasma membrane (it does). It doesn't say anything about entering the bloodstream (as in being secreted by a cell). It just says that once it's in the bloodstream, it doesn't need to bind anything to remain soluble.

 

[bellowbruins]

thankyou all for taking your time to answer my questions.