Multiple Choice
When does passive transport occur across a cell membrane?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
In the context of passive transport, osmosis is defined as the movement of which substance across a selectively permeable membrane?
A
Solute molecules moving from higher solute concentration to lower solute concentration through a membrane channel
B
Water molecules moving from higher solute concentration (lower water potential) to lower solute concentration (higher water potential)
C
Ions moving against their electrochemical gradient using ATP-dependent pumps
D
Water molecules moving from lower solute concentration (higher water potential) to higher solute concentration (lower water potential)
Verified step by step guidance1
Understand that osmosis is a specific type of passive transport involving the movement of water molecules across a selectively permeable membrane.
Recall that water moves from an area of higher water potential (which corresponds to lower solute concentration) to an area of lower water potential (which corresponds to higher solute concentration).
Recognize that solute molecules do not move during osmosis; instead, water moves to balance solute concentrations on both sides of the membrane.
Note that osmosis does not require energy input (ATP) and occurs down the water potential gradient, unlike active transport mechanisms such as ion pumps.
Therefore, the correct description of osmosis is: water molecules moving from lower solute concentration (higher water potential) to higher solute concentration (lower water potential) across a selectively permeable membrane.
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