Multiple Choice
Which of the following statements about diffusion is true?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
In the context of passive transport, what is the primary mechanism by which water enters and exits a cell across the plasma membrane?
A
Active transport via ATP-powered pumps that move water molecules against their concentration gradient
B
Osmosis, often facilitated by aquaporin channels, driven by differences in solute concentration (water potential) across the membrane
C
Endocytosis and exocytosis of bulk water in membrane-bound vesicles under resting conditions
D
Simple diffusion of water through ligand-gated ion channels that open only in response to signaling molecules
Verified step by step guidance1
Understand that passive transport involves the movement of substances across the plasma membrane without the use of cellular energy (ATP).
Recall that water movement across the membrane is primarily driven by differences in solute concentration, which creates a water potential gradient.
Identify osmosis as the specific type of passive transport where water moves from an area of lower solute concentration to an area of higher solute concentration.
Recognize that aquaporins are specialized protein channels in the plasma membrane that facilitate the rapid movement of water molecules during osmosis.
Conclude that water enters and exits the cell mainly through osmosis, often facilitated by aquaporin channels, driven by solute concentration differences across the membrane.
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