Multiple Choice
Which of the following best explains diffusion in the context of passive transport across cell membranes?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
Which of the following statements is true of osmosis in cells?
A
It is the movement of solute molecules from lower solute concentration to higher solute concentration across a membrane, requiring ATP.
B
It is the movement of water across a membrane only when aquaporin channels are absent.
C
It is the net movement of water across a selectively permeable membrane from lower solute concentration (higher water potential) to higher solute concentration (lower water potential).
D
It is the net movement of water across a membrane from higher solute concentration to lower solute concentration.
Verified step by step guidance1
Step 1: Understand the definition of osmosis. Osmosis is the movement of water molecules across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.
Step 2: Recognize that osmosis does not involve the movement of solute molecules, but rather the movement of water molecules to balance solute concentrations on both sides of the membrane.
Step 3: Note that osmosis is a passive process and does not require ATP (energy input) because water moves down its concentration gradient.
Step 4: Understand the role of aquaporins, which are protein channels that facilitate water movement, but osmosis can still occur without them, just at a slower rate.
Step 5: Conclude that the correct statement must describe osmosis as the net movement of water from lower solute concentration (higher water potential) to higher solute concentration (lower water potential) across a selectively permeable membrane.
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