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As used in the text, what does the word “channel” most nearly mean?
The cell membrane acts as a selective barrier, controlling what enters and exits the cell. For charged particles like ions, which cannot easily pass through the lipid bilayer, specialized proteins are essential. These proteins form a hydrophilic pore, or · *channel · *, through the membrane. This structure allows specific ions, such as sodium or potassium, to move down their electrochemical gradient and into or out of the cell. The opening and closing of these pathways are often tightly regulated, ensuring the cell maintains its delicate internal balance.