MadSci Network: Cell Biology |
Hi Karim, this is a very good question! Well, it depends on what KIND of hormone you are talking about. Generally, there are two kinds: protein hormones and lipid (steroid) hormones. Both kinds of hormones have receptors, but the work differently to make changes in cells. Protein or peptide hormones are soluble or polar. Because the plasma membrane is made out of a lipid bilayer- peptide hormones can't pass through. So, in order for a hormone to send a signal to a cell, it binds to a protein rececptor on the surface of the cell that is anchored in the plasma membrane. The receptor can bind specifically to the peptide hormone because the shape or binding pocket of the receptor is shaped especially for the structure of the peptide hormone. Once the receptor is bound to the hormone, the inside portion of the receptor (the cytoplasmic face of the receptor) is "activated" and can send messages inside the cell. Steroid hormones are derived from the lipid, cholesterol, and are nonpolar. They can readily pass through any cell's plasma membrane. But, these hormones also have receptors. The receptors of steroid hormones are not membrane-bound but are floating in the cytoplasm. These receptors also have a binding pocket that is shaped especially for the structure of the steroid hormone. Upon binding, the receptor now can "activate" a transciption factor, and induce transcription of specific genes to make proteins. The steroid hormone can direct that transcription and expression of these genes into protein while the peptide hormone works to activate proteins that are already made. I hope this helps! Sincerely, Elena Rodriguez
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