How drugs bind: affinity, shape and binding site
Explains what a drug physically does at its target: how tightly it binds (affinity), why its shape matters, where on the receptor it binds, and how long it stays.
Where this fitsConnects to 2 · Unlocks 3
- Connects to
- Locks and keys: receptor specificity, agonists and antagonists — Builds directly on the lock-and-key picture of the synapse.
- The two journeys: pharmacokinetics and pharmacodynamics — This is the pharmacodynamics half of the two journeys.
- Unlocks
- Agonists: full, partial, inverse and biased — Once a drug binds, it can mimic the messenger (agonist)…
- Antagonists and allosteric modulators (PAMs and NAMs) — …block it (antagonist), or tune the receptor from another site (modulator).
- Dose-response curves: potency, efficacy, slope and variability — Affinity is what 'potency' on a dose-response curve is built on.
Orient
In contrast to pharmacokinetics (the study of what the body does to drugs), pharmacodynamics is the study of what a drug does to the body. Neurotransmitters are endogenous; drugs are exogenous and can bind to the same receptors, but they can bind more/less readily than the endogenous NT (binding affinity), mimic or block the endogenous NT (agonism or antagonism), and be more or less specific in binding sites. Shape matters: isomer – same chemical composition, different arrangement.
Course terms
Your professor's wording, word for word from the slides. Learn the term and this definition — the explanation underneath is only there to help it make sense.
- Pharmacodynamics
“pharmacodynamics is the study of what a drug does to the body”Slides 05, p. 2
Pharmacokinetics is the reverse: what the body does to drugs.
- Binding affinity
“They can bind more/less readily than the endogenous NT”Slides 05, p. 6
How readily a drug binds its receptor compared with the neurotransmitter.
- Isomer
“Isomer – same chemical composition, different arrangement”Slides 05, p. 7
Like left and right hands; marked L/D or R/S, e.g., levoamphetamine vs. dextroamphetamine, R- vs. S-ketamine.
- Racemic mixture
“Often combined (racemic mixture; easier to produce)”Slides 05, p. 7
Both isomers together.
- KD / Ki
“Concentration needed to occupy 50% of target binding site”Slides 05, p. 33
Measured in molar concentration; lower values mean higher affinity.
- Orthosteric site
“Drug itself does not bind to endogenous NT site (orthosteric) on the receptor, but alters receptor’s binding affinity for NT”Slides 05, p. 16
Orthosteric = the neurotransmitter's own binding site; drugs that bind elsewhere bind an allosteric site.
From your course: Course slides 05, pp. 2–7 · Course slides 05, pp. 16, 32–33
Tip: the ← and → keys move through the lesson.
Full lesson: Reversible receptor binding