BIOC 3560 Study Guide - Final Guide: Acetylcholine Receptor, Signal Transduction, Electrochemical Gradient
21 Oct 2016
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Document Summary
Signal-transducing systems generally: are very specific, amplify the initial signal, signaling is mediated by modular components with (partly) interchangeable parts, show desensitization and adaptation to a persistent signal, have mechanisms to integrate conflicting signals, specificity. ~ signal molecule fits binding site on its complementary receptor. Only the correct ligand (or signal) will stimulate a given receptor. Multicellular organisms have additional specificity, as many receptors are present in only in certain cell types. 3 factors account for extraordinary sensitivity of signal transducers: Receptors have very high affinity for their ligands (kd ~ 10-10 m - picomolar) So very low ligand concentrations can activate. Cooperativity in the ligand-receptor interaction results in large changes in activity upon ligand binding. Once activated, enzyme cascades amplify the signal. The number of affected molecules increases geometrically in an enzyme cascade: amplification. Amplifications of several orders of magnitude w. in milliseconds = fast and potent response: modularity.
