BIOM 3090 Chapter Notes - Chapter 2: Cell Membrane, Extracellular Fluid, Signal Transduction
28 Nov 2017
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Document Summary
Most drugs (a. k. a. ligands) exert their effects (initiate, enhance, diminish or terminate biochemical pathways) by binding to receptors in the plasma membrane of cells. The receptor, its cellular target and any intermediary molecules are referred to as the signal transduction pathway (a. k. a. receptor-effector system). The effects can be immediate (ms to s) or delayed (min to hours) and depend on actions of effector proteins and often second messengers that modulate cellular targets. The drug effect is generally proportional to the percentage of receptors occupied by drug. Also, the fraction of drug receptors occupied by the drug is dependent on drug concentration in the extracellular fluid. In order for drugs to interact with receptors, they need to possess adequate size, charge, shape and atomic composition. The lower limit (100 mw) is the minimum size needed to impart specificity of action while the upper limit (1000 mw) is the size limit allowing reasonable movement in the body to sites of action.
