KEY TAKEAWAYS •
Osmosis involves the transfer of water across a semipermeable membrane.
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Simple diffusion involves the transfer of a solute from an area of high concentration to an area of low concentration, not necessarily across a membrane.
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Aquaporins allow water to pass through a membrane more easily than would happen through osmosis.
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Facilitated diffusion does not require energy, while active transport usually requires ATP energy.
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The presence of an electrochemical gradient will drive the secondary active transport of certain molecules but the primary active transport happens with the sodium-potassium ATPase pump and other pumps.
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The resting membrane potential of a cell is maintained by the sodium-potassium ATPase pump but, in certain cells, there are voltage-gated channels that allow for depolarization and repolarization.
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