Week 12
Key Terms:
- Active transport
- Uniporter
- Facilitated diffusion
Active transport - Channels that require ATP to transport molecules across the membrane against their concentration gradient. An example of active transport is the sodium-potassium pump, which uses ATP to pump three sodium ions outside the cell and pumps two potassium ions into the cell. This establishes a concentration gradient across the cell membrane and a net negative charge inside the cell and a net positive charge outside the cell.
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Uniporter - A channel that allows for facilitated diffusion and transports one molecule at a time across the plasma membrane by undergoing conformational change. Uniporters transfer molecules at a rate faster than the rate of simple diffusion but slower than the rate of the transfer of molecules through ion channels.
Facilitated diffusion - Channel that transports molecules down their concentration gradient by undergoing conformational change and includes carrier proteins and channel proteins.
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