Question

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cell membrane and transport: learn how transporters keep cells healthy
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question 5 of 13
a key characteristic of active transport across a cell membrane is that it:
moves substances against their concentration or electrochemical gradient, requiring energy.
always involves the movement of water molecules via osmosis without energy input.
occurs spontaneously for all types of molecules without the need for membrane proteins.

Explanation:

Active transport is the movement of molecules or ions across a cell - membrane from an area of lower concentration to an area of higher concentration. This process requires energy (usually in the form of ATP) as it goes against the concentration or electrochemical gradient. Osmosis is the movement of water molecules and is a form of passive transport. Also, most transport across the cell - membrane requires membrane proteins, and spontaneous movement without energy input is passive transport.

Answer:

Moves substances against their concentration or electrochemical gradient, requiring energy.