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Ion Channels |
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It is known that the electrical signals in living tissue are caused by ions moving in and out through cell membranes. The primary elements that cause this are Na+ and K+. Ion channels have to ba able to let one type of ion but not the other through. MacKinnon discovered how potassium ions but not sodium ions are allowed through a certain ion filter. The potassium ions are surrounded by water molecules. The potassium ions can slide through because the distance between the oxygen in the filter and the potassium ion is the same as the distance between the the potassium ion and the oxygen in the water around the potassium. This allows the potassium to slide right through because it comes out of it's water solution. The sodium can not pass through because it does not fit |
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http://www.kve.se/KVA_Root/files/newspics/DOC_200310811020_50163460823_chempuben.asp |
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between the oxygen atoms in the filter, so therefor staus in solution. MacKinnon also found what controls the opening and closing of the channels. It is caused by a gate at the bottom of the channel which opens and closes a molecular "sensor". These senors react to certain signals, for example an electrical voltage over the cell membrane. The sensors are connected to different ion channels that respond to many diferent signals. The above picture is a model of the ion channel. |
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