Pharmacology Principles, Receptors, and Enzyme Targets

Vocabulary flashcards covering pharmacology concepts, receptor dynamics, mass action, enzymatic inhibition, and GPCR signaling pathways.

Pharmacology

The study of medications, chemical compounds, or substances that interact with living systems (molecules, cells, tissues, or organisms) to produce a biological effect.

Pharmacokinetics

The branch of pharmacology that studies what the body does to a drug, encompassing absorption, distribution, metabolism, and excretion (ADME).

Pharmacodynamics

The branch of pharmacology that studies what drugs do to the body, focusing on biochemical or physiological effects through their mechanism of action.

Receptor Theory

A foundational concept described by Paul Ehrlich stating that drugs act by binding to specific cellular targets (receptors), and that substances do not act unless bound.

Lock and Key Model

A model describing drug-receptor interactions where the drug acts as the key and the receptor acts as the lock into which the key must fit to produce a biological response.

Dissociation Constant ($K_d$)

The concentration of a drug at which 50% of the total receptor population is bound to the drug forming a drug-receptor complex, and 50% remains uncoupled or free.

Affinity

The strength of binding between a drug and its receptor, which maintains an inverse relationship with the dissociation constant ($K_d$).

Competitive Inhibition

A form of enzymatic inhibition where an inhibitor drug binds directly to the active catalytic site of an enzyme and competes with the physiological substrate.

Non-Competitive Inhibition

A form of enzymatic inhibition where an inhibitor binds to an allosteric or regulatory site on an enzyme rather than the active site, altering the enzyme's activity.

Ion Channels

Transmembrane proteins that regulate ion flux across the cell membrane to control cellular excitability, serving as targets for antiarrhythmics, psychiatric drugs, and muscle relaxants.

Transporters

Transmembrane proteins that facilitate the movement of essential substances across membranes, serving as drug targets for agents like proton pump inhibitors.

G Protein-Coupled Receptors (GPCRs)

Cell membrane receptors composed of seven transmembrane alpha-helices that trigger intracellular signaling cascades upon binding an extracellular ligand or drug.

First Messenger

The extracellular ligand or drug that initiates cellular signaling by binding to its specific cell-surface receptor site.

Second Messengers

Intracellular signaling molecules (such as cAMP, DAG, or $IP_3$) generated following receptor activation that mediate downstream cellular and biological effects.

$G_s$ Protein

A stimulatory G protein that activates adenylyl cyclase upon activation, increasing intracellular levels of cyclic AMP (cAMP) to promote stimulatory cellular responses.

$G_i$ Protein

An inhibitory G protein that inhibits adenylyl cyclase upon activation, decreasing intracellular cyclic AMP (cAMP) levels to promote inhibitory cellular responses.

$G_q$ Protein

A stimulatory G protein that activates phospholipase C (PLC), leading to the generation of diacylglycerol (DAG) and inositol trisphosphate ($IP_3$) as second messengers.

Beta-Arrestin

An intracellular protein that binds to phosphorylated, activated GPCRs to uncouple them from G proteins and mediate receptor endocytosis or internalization.

Receptor Desensitization

A physiological homeostatic mechanism where continuous or repeated receptor stimulation leads to beta-arrestin binding and receptor internalization, diminishing drug responsiveness.