It can exist in - a gated ion channel - can exist in one or two states.

它们能够存在于,门控离子通道有一种或者两种状态

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The one that's on the top here is called ligand-gated ion channel and an ion channel is a protein that sits in the surface of a cell.

最上面的这个叫作配体门控离子通道,离子通道是一类位于细胞表面的蛋白

耶鲁公开课 - 生物医学工程探索课程节选