BIOL 2021 Lecture 5: Chapter 11- Transport of Small Molecules (Part 2).docx
19 Apr 2015
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Ion channels: unlike transporters, channels form pores across membranes, porins; the channels in the outer membranes of bacteria, mitochondria, and chloroplasts, have relatively large and permissive pores, and it would be disastrous if they directly connected the inside of a cell to an extracellular space. Na+, k+, ca2+, or cl to diffuse rapidly down their electrochemical gradients across the lipid bilayer: we will see that the ability to control ion fluxes through these channels is essential for many cell functions, nerve cells (neurons), in particular, have made a specialty of using ion channels, and we will consider how they use many different ion channels to receive, conduct, and transmit signals, some characteristics of an ion channel are, they have a narrow hydrophilic pore, have a selectivity filter: region where the pore narrows to atomic dimensions so that only ions of appropriate size and charge can pass in single file.
