Science Buddies: "Ask an Expert"

This isn't an interview/science questions but I'm having trouble understanding a concept that I'm hoping to lead into a research idea so I'd like some input.

I'm curious as to how steroid hormones are able to move through a lipid bilayer physically without the use of a membrane transporter. I understand that the steroid is a cholesterol derivative that is lipophilic and that inside the bilayer is a preferred energy state but how does it physically cross the membrane? Does it cause a conformational change in the membrane that allows the steroid to pass through or does the steroid undergo some conformational change to pass through the membrane?

Any help understanding the biophysics of this movement would be greatly appreciated!

Hi,

The lipid bilayer is fluid. Components are constantly moving around (have you heard the term
lipid rafts'?), changig the composition of the membrane in certain areas. The steroid hormones pass through the membrane by diffusion, so, yes, there is a slight conformational change in the membrane as the hormone squeezes through. picture it similar to the movement of bushes/shrubary as you push your way through a dense forest - they move just enough for you to get by.

This paper might give you the level of detain you are looking for:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1304487/

General info:
http://www.physiologyweb.com/lecture_no ... ility.html

Let me know if you have further questions, or if I did not answer adequately.

Tonya