Cytoplasmic residues of the receptor are thus the effector region of the molecule. Several distinctive variations in receptor structure have been identified. As depicted below, some receptors are simple, single-pass proteins; many growth factor receptors take this form.
In some cases, other integral membrane proteins interact with the receptor to modulate its activity. Some types of receptors cluster together in the membrane after binding hormone. Finally, as elaborated below, interaction of the hormone-bound receptor with other membrane or cytoplasmic proteins is the key to generation of second messengers and transduction of the hormonal.
The firefighters would then rapidly go to work pouring water on the fire, setting up roadblocks and the like. They would also probably activate other "players such as police and fire investigators that would come in later to try and determine the cause of the fire.
Second Messenger Systems Consider what would happen if, late at night, you noticed a building on fire. Hopefully, you would dial 911 or a similar emergency number. You would inform the dispatcher of the fire, and the dispatcher would, in turn, contact and "activate" a number of firemen.
Note that not only do multiple hormones utilize the same second messenger system, but a single hormone can utilize more than one system. Understanding how cells integrate signals from several hormones into a coherent biological response remains a challenge).
Protein and peptide hormones, catecholamines like epinephrine, and eicosanoids such as prostaglandins find their receptors decorating the plasma membrane of target cells. Binding of hormone to receptor initiates a series of events which leads to generation of so-called second messengers within the cell (the hormone is the first messenger).
Others, such as the receptor for insulin, have more than one subunit. Another class, which includes the beta-adrenergic receptor, is threaded through the membrane seven times. Receptor molecules are neither isolated by themselves nor fixed in one location of the plasma membrane.
Transmembrane domains: Hydrophobic stretches of amino acids are "comfortable" in the lipid bilayer and serve to anchor the receptor in the membrane. Cytoplasmic or intracellular domains: Tails or loops of the receptor that are within the cytoplasm react to hormone binding by interacting in some way with other molecules, leading to generation of second messengers.
The second messengers then trigger a series of molecular interactions that alter the physiologic state of the cell. Another term used to describe this entire process is signal transduction. Structure of Cell Surface Receptors Cell surface receptors are integral membrane proteins and, as such, have regions that contribute to three basic domains: Extracellular domains: Some.
In the scenario described, you are the "first messenger the dispatcher is "receptor the firefighters are "second messengers". Currently, four second messenger systems are recognized in cells, as summarized in the table below.
Importantly, once the fire is out (or the building totally destroyed the firemen go back to the station and to sleep. The community response to a fire is, at least in some ways, analogous to a second messenger system involved in a hormone's action.
"Although the risks of insufficient thyroid hormone during pregnancy are established said study author Samuel Refetoff, MD, professor of medicine and pediatrics and the committees on genetics and molecular medicine at the University of Chicago, "we have not, until now, been able to determine the consequences of an excess.