Practice Exam Question

[Romaboy]

Hey guys,
I am currently Insight 2009 practice exam and have finished it.
I've started to mark it and the answers say with this one that A is correct.
I thought it was C.
Last I heard, was that Protein-based hormones bind to receptors on the Plasma Membrane.
Help would be appreciated thanks

Question 16
Thyroxine is a hormone which is released from the thyroid gland into the bloodstream. It is
transported through the circulatory system until reaching target cell receptors around the body.
Thyroxine is synthesised from the amino acid tyrosine and
A. can move through the plasma membrane of the cell because it is small and hydrophobic.
B.  can move through the plasma membrane of the cell because it is small and hydrophilic.
C.  binds with a receptor protein on the plasma membrane.
D.  binds with a target protein on the plasma membrane.

[APPLEhead]

Thyroxin is an amino acid derivative hormone, and while those hormones usually have protein receptors on the surface, thyroxin is the exception. Thyroxin also has a long life span and can pass across the cell membrane.

[Romaboy]

Thanks You

[Romaboy]

Thyroxin is an amino acid derivative hormone, and while those hormones usually have protein receptors on the surface, thyroxin is the exception. Thyroxin also has a long life span and can pass across the cell membrane.

Also, is Thyroxin the only exception?

[APPLEhead]

lol I don't know

Hopefully they won't ask for this on the exam...

[spherelin]

I chose B, but only because my teacher knocked it into my head multiple times that is an exception. I HONESTLY got so annoyed because i was like WHUT IT'S AN AMINOACID DERIVATIVE.. but yeah.... Does anyone know other examples of Aminoacid derivatives that ARE hydrophilic though?
Aside from that, don't worry, i dont think that the actual exam will include such a contentious question...... at least i hope, but even if it is included... WELL, WE ALL KNOW THE ANSWER

[InsaneMcFries]

Here's the thing, I don't think all amino acid derivative hormones are able to pass through the cell membrane. That question required knowledge that would be explained in detail in a VCAA exam.

A hard question on VCAA would give all of that information but include that it is hydrophobic perhaps? Either way it is unlikely.