Multiple Choice
In osmosis, water moves across a selectively permeable membrane from an area of which condition to an area of which condition?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
Which of the following is an example of passive transport across a cell membrane?
A
Uptake of extracellular fluid into the cell by pinocytosis
B
Transport of glucose into a cell against its concentration gradient using a symporter coupled to the gradient
C
Pumping out of the cell and into the cell using ATP (sodium-potassium pump)
D
Movement of water through aquaporin channels down its concentration gradient (osmosis)
Verified step by step guidance1
Understand the definition of passive transport: it is the movement of molecules across a cell membrane without the use of cellular energy (ATP), typically down their concentration gradient.
Review each option to determine if energy is required or if the movement is down a concentration gradient:
Pinocytosis involves the cell engulfing extracellular fluid, which requires energy, so it is an active process, not passive transport.
Transport of glucose against its concentration gradient using a symporter coupled to the Na+ gradient involves moving substances against their gradient and relies on energy indirectly, so it is active transport.
Pumping Na+ out and K+ into the cell using ATP (sodium-potassium pump) directly uses energy, so it is active transport.
Movement of water through aquaporin channels down its concentration gradient (osmosis) does not require energy and occurs passively, making it an example of passive transport.
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