By my understanding, a substance that binds to a receptor and activates it is called an agonist, while a substance that binds to a receptor without activating it is called an antagonist. (Wiki) What is the fundamental difference between binding to a receptor and activating it?

EDIT: I guess the receptor is a complex enough beast that fitting into it and staying there can be accomplished by some sections of the interface being completed, without necessarily completing the "usual" interfacing process between the receptor and its agonist -- thereby blocking the receptor geometrically without imparting the proper energy to it chemically.

  • $\begingroup$ This is similar to competitive inhibition of enzymes. $\endgroup$
    Mar 17, 2016 at 6:25

1 Answer 1


The details of activation vary by receptor of course, but talking in the popular key-lock picture:

  • An agonist is a key, that fits the lock and opens ("activates") it.

  • An antagonist is a key that you can put into the keyhole, but it does not open the lock. What this means is: while the "wrong" key is in the keyhole, you won't be able to open the door, even if you have the correct key, as long as the wrong key is in the keyhole.

As far as Wikipedia goes, the articles for Agonist (and the links contained therein) might be more informative than the one you quoted.



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