离子通道具有两个显著特征:一是具有离子选择性, 第二个特征是离子通道是门控的。 离子通道又区分为电压门通道( voltage-gated channel)、配体门通道( ligand- gated channel)和压力 激活通道( stress-activated channel) lon concentration Membrane FIGURE 15-9: Transmembrane forces gradient electrical potential acting on Nat ions. As with all Ions, the movement of Na+ ions across the plasma Inside Outsid Inside Outsid membrane is governed by the sum of two separate forces-the membrane 12 mM 145mM electric potential and the ion concentra Na tion gradient In the case of Nat ions, these forces usually act in the same direction △Gc=-1.45 kcal/mol△Gm=-1.61 kcal/ mol Free-energy change during transport of Na* from outside to inside Inside Outside △G=△Ga+△Gm=-3.06 kcal/mol离子通道具有两个显著特征：一是具有离子选择性， 第二个特征是离子通道是门控的。 离子通道又区分为电压门通道（voltage-gated channel）、配体门通道（ligand-gated channel）和压力 激活通道（stress-activated channel）