Cell transport

Science

Definition

Cell transport refers to the movement of substances across the cell membrane. Passive transport (diffusion, osmosis, facilitated diffusion) requires no energy, while active transport uses ATP to move molecules against their concentration gradient.

Examples

  • Oxygen moves into cells by simple diffusion from high to low concentration
  • The sodium-potassium pump actively transports 3 Na⁺ out and 2 K⁺ into the cell using ATP
  • Water moves across membranes by osmosis, which is why red blood cells swell in hypotonic solutions
Key Fact

Passive transport moves molecules DOWN the concentration gradient (no ATP); active transport moves them AGAINST it (requires ATP).

Related Terms

Cell membrane Membrane transport Concentration Atp cycle

Study This Concept

Practice cell transport with free review games in these units:

Biology Unit 2: Cell Biology