BIOL 2P03 Lecture Notes - Lecture 13: Axon Terminal, Exocytosis, Action Potential
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5 Mar 2016
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Positively charged ions are known as cations. Negatively charged ions are known as anions. Unequal movement of charged molecules across the membrane results in a separation of charge. Biologically speaking, this is known as the membrane potential. Ions cannot simply diffuse across the plasma membrane. They require pumps, transporters (carriers) and ion channels. Ion channels are transmembrane proteins that create water filled pores in the plasma membrane that are permeable to select ions. Ion channels can exist in open and closed states. When in the closed state, ions cannot pass through the ion channel. When in the open state, ions can pass through the ion channel. Ion channels will reversibly switch between open and closed states. Movement from closed state to open state is known as activation. Movement from open state to closed state is known as deactivation. Some ion channels can exist in a second type of closed state known as an inactivated state.