Active transport requires energy in order to move molecules the concentration gradient while simple and facilitated diffusion require no energy to move molecules the concentration gradient.

Active transport requires energy in order to move molecules against the concentration gradient while simple and facilitated diffusion require no energy to move molecules down the concentration gradient.

Explanation:

Active transport requires energy as the substance move from low concentration to high concentration (substances move against concentration gradient).

For example, Sodium-potassium pump.

Passive transport does not require energy as the substance move from high concentration to low concentration (substances move only down their concentration gradient).

It is of two types: Simple and facilitated transport.

For example, Osmosis.

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