Uniporters, symporters and antiporters | Biology | Khan Academy | Summary and Q&A

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August 4, 2015
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Uniporters, symporters and antiporters | Biology | Khan Academy

TL;DR

Different types of transportation across cellular membranes include diffusion, facilitated diffusion, primary active transport, secondary active transport, symporters, and antiporters.

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Questions & Answers

Q: What is the difference between diffusion and facilitated diffusion?

Diffusion is the passive movement of small, nonpolar molecules down their concentration gradient, while facilitated diffusion allows molecules with charge or larger sizes to flow down their concentration gradient through channels or gated tunnels.

Q: What is primary active transport?

Primary active transport is the direct use of ATP to transport molecules against their concentration gradient. An example is the sodium-potassium pump, which uses ATP to pump sodium out of the cell and potassium into the cell.

Q: How does secondary active transport work?

Secondary active transport uses the energy from an established concentration gradient to transport other molecules. Symporters, like the sodium-glucose symporter, leverage the flow of sodium down its concentration gradient to transport glucose against its concentration gradient.

Q: What is the difference between symporters and antiporters?

Symporters transport two substances in the same direction, with one substance flowing down its gradient and providing energy for the other substance to be transported against its gradient. Antiporters transport substances in opposite directions, with one substance flowing down its gradient while another substance is transported against its gradient.

Summary & Key Takeaways

  • Molecules can be transported across cellular membranes through diffusion, which occurs when small, nonpolar molecules move down their concentration gradient.

  • Facilitated diffusion allows molecules with charge or larger sizes to flow down their concentration gradient through channels or gated tunnels.

  • Active transport requires energy and can be primary, where ATP is directly used to transport molecules against their gradient, or secondary, where the energy from an established gradient helps transport other molecules.

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