what is an analogy for active transport and passive transport

Question

anonymous · Answer

active transport need ATP, passive transport don't
both involve movement of substance across membrane. Active transport involve movement substance against its concentration gradient, but passive transport involve movement down the concentration gradient.

anonymous · Answer

The question asks for an example of active vs passive transport.  The movement of molecules through membranes based only on concentrations is passive, requiring no energy expendature such as water moving through a membrane as in osmosis.  Active transport requires an energy expenditure (usually ATP) and selectively moves substances against a concentration gradient.  For instance sodium is transported into many cells by carriers in the cell membrane and requires ATP as an energy source.  The transport systems are vitaal for life.

rogue · Answer

Passive transport analogy... Perfume diffuses throughout the room from a region of high concentration to low concentration. Active transport analogy... Hard to think of, so I'll refer you to this: http://wiki.answers.com/Q/Give_a_real_life_analogy_to_diffrentiate_between_passive_transport

anonymous · Answer

Active transport analogy: Swimming against the current (water current)
Passive diffusion analogy: Swimming with the current (water current)