Pan-African flag - History. 1  The flag was created in 1920 by members of UNIA in response to the enormously popular 1900 coon song Every Race Has a Flag but the Coon. [4] which has been cited as one of the three songs that firmly established the term coon in the American vocabulary.
A ligand is any molecule that binds to a specific site on a protein or other molecule. In this case, the estrogen hormone 17-beta-estradiol is the ligand, and the estrogen receptor is the protein. Binding turns on, or activates, a hormone receptor.
In cell biology, receptors are special structures that can be found in cell membranes. These are made of protein molecules such as glycoproteins. Receptors bind (attach) to specialised molecules. If the receptor has this molecule, it is activated, but if it does not it is deactivated.