AP Biology / Unit 2: Cell Structure and Function
2.5 Membrane Transport
Notes
- Passive transport: down the concentration gradient, no energy (diffusion, osmosis).
- Active transport: against the gradient, uses energy (ATP), e.g. the Na⁺/K⁺ pump.
- Endocytosis/exocytosis: move large materials in vesicles.
Practice
Moving a molecule from low to high concentration requires:
Against the gradient costs energy.
The sodium-potassium pump moves:
Builds the membrane potential.
A cell releasing hormones in vesicles uses:
Vesicles fuse with the membrane.
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