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| the first step in the action of any intercellular chemical messenger is the binding of the messenger to specific target-cell proteins known as __________ or ___________. |
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Definition
1) receptors
2) or receptor proteins
...a chemical messenger is a ligand, and the receptor protein has a binding site for that ligand.
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Term
| the binding or a messenger to a receptor protein initiates a sequence of events in the cell leading to the cell's response to that messenger, a process called __________ |
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| plasma membrane receptors are ____________; that is, they span the entire membrane thickness. |
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| what is the nature of the receptors with which intercellular chemical messengers combine? |
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Definition
| -they are proteins of glycoproteins located either in the cell's plasma membrane or inside the cell, mainly in the nucleus. |
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Definition
| the ability of a receptor to bind only one type or a limited number or structurally related types of chemical messengers |
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Definition
| the degree to which receptors are occupied by messengers. if all are occupied, the receptors are fully saturated; if half are occupied, the saturation is 50 percent, and so on.. |
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Term
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Definition
the ability of different molecules very similar in structure (--> antagonist/agonist) to compete with each other to combine with the same receptor.
e.g. if physicians may wish to interfere with the action of a particular messenger, so.. they may administer competing molecules that are similar enough to the endogenous messenger that they bind to the receptors for that messenger. |
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Definition
a molecule [drugs] that competes for a receptor with a chemical messenger normally present in the body. the antagonist binds to the receptor but does not trigger the cell's respose.
(e.g. Antihistamines) |
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Definition
a chemical messenger that binds to a receptor and triggers the cell's response; often refers to a drug that mimics a normal messenger's action.
(e.g. Decongestants) |
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Definition
| a decrease in the total number or target-cell receptors for a given messenger; may occur in response to chronic high extracellular concentration of the messenger |
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Definition
| an increase in the total number or target-cell receptors for a given messenger; may occur in response to a chronic low extracellular concentraton of the messenger |
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Definition
| the increased responsiveness of a target cell to a given messenger; may result from up-regulation of receptors |
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Definition
| the strength with which a chemical messenger binds to its receptor |
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Term
| in theory, the receptor functions as .... |
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Definition
a molecular "switch" that elicits the cell's response when 'switched on' by the messenger binding to it
...also!
a single type of receptor can be used to produce quite different responses in different cell types (not just one)....
[e.g. epinephrine causes the smooth muscles or certain blood vessels to contract, but, via the same type of receptor, causes endocrine cells in the pancreas to secrete less insulin] |
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Term
| a single cell may also contain more than one different receptor type for a single messenger. |
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Definition
| in fact, a single cell usually contains many different receptors for different chemical messengers |
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Term
| what are the sequences of events by which the binding of a chemical messenger (hormone, neurotransmitter, or pancrine/autocrine agent) to a receptor causes the cell to respond? |
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Definition
-receptor activation: change in receptor conformation caused by combination of messenger with receptor
receptor activation is always the initial step leading tothe cell's responses to the messenger. |
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Term
receptor activation can take the form of changes what five types of ultimate response?
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Definition
1) the permeability, transport properties, or electrical state of the cell's plasma membrane
2) the cell's metabolism
3) the cell's secretory activity
4) the cell's rate or proliferation and differentiation
5) the cell's contractile activity
(these changes are all directly due to alterations of particular cell proteins) |
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| defines the strength of receptor binding to a messenger |
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Definition
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| reflects the fact that a receptor normally binds only to a single messenger |
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