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Hormones Question Biology!

Why does glucocorticoid hormone enter cells via a transport protein in the plasma membrane? Aren't steroids lipid-soluble, hence able to diffuse through the phospholipid bilayer directly?

Also if they are secreted by endocrine glands into the bloodstream, how do they travel to the target cell, because I thought steroids were not water-soluble?

I got the information from:

https://www.youtube.com/watch?v=Y3a4_PBHNx8&list=PLXwnjgs_UWpIyKAZ9yaEUbv8Sz1AMve45&index=7

Thanks! :smile:
Moved to the biology section of the website. They may have an answer for you :h:
Original post by champion1
Why does glucocorticoid hormone enter cells via a transport protein in the plasma membrane? Aren't steroids lipid-soluble, hence able to diffuse through the phospholipid bilayer directly?

Also if they are secreted by endocrine glands into the bloodstream, how do they travel to the target cell, because I thought steroids were not water-soluble?

I got the information from:

https://www.youtube.com/watch?v=Y3a4_PBHNx8&list=PLXwnjgs_UWpIyKAZ9yaEUbv8Sz1AMve45&index=7

Thanks! :smile:


As you mentioned, glucocorticoid hormones are steroid hormones, and are therefore lipid-soluble. That being said, glucocorticoid hormones enter the cell through protein transporters in the plasma membrane for more efficient transport than diffusion; the cell can also exert a degree of control over the glucocorticoid hormone entrance using plasma transporters than simple passive diffusion.

Since glucocorticoid hormones are fat-soluble, they are released from endocrine glands directly into the bloodstream and are transported bound to specific carrier proteins, called corticosteroid-binding globulin (aka. Transcortin). The production of Transcortin occurs in the liver and is increased in response to oestrogens.

Take a look at this 'Action of Glucocorticoid Hormone' animation, I found it really useful:

http://highered.mheducation.com/sites/9834092339/student_view0/chapter16/action_of_glucocorticoid_hormone.html
(edited 9 years ago)
Reply 3
Original post by loukas2993
As you mentioned, glucocorticoid hormones are steroid hormones, and are therefore lipid-soluble. That being said, glucocorticoid hormones enter the cell through protein transporters in the plasma membrane for more efficient transport than diffusion; the cell can also exert a degree of control over the glucocorticoid hormone entrance using plasma transporters than simple passive diffusion.

Since glucocorticoid hormones are fat-soluble, they are released from endocrine glands directly into the bloodstream and are transported bound to specific carrier proteins, called corticosteroid-binding globulin (aka. Transcortin). The production of Transcortin occurs in the liver and is increased in response to oestrogens.

Take a look at this 'Action of Glucocorticoid Hormone' animation, I found it really useful:

http://highered.mheducation.com/sites/9834092339/student_view0/chapter16/action_of_glucocorticoid_hormone.html


Thank you! This is really helpful. Btw the animation from your link is the same one as the animation in my link, but thanks ayway - the animation is really useful. :smile:

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