(1) Cell membranes (plasma membranes) help organisms maintain homeostasis by controlling what substances may enter or leave cells. (2) Some substances can cross a cell membrane through passive transport, while other substances can only cross a cell membrane through active transport. What is the difference between active and passive cellular transport?

Explanation:

Active cellular transport:

It is the movement of molecules against the concentration gradient  (from low concentration to high). Active transport requires expense of energy supplied by ATP.It is a rapid way to transport of large sized molecules.

Passive cellular transport:

It is the movement of molecules along the concentration gradient (from high concentration to low).Passive transport does not require expense of energy. It is a slow process and small sized molecules get transprorted.

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