Multiple Choice
In passive transport by simple diffusion, how does the magnitude of the concentration gradient across a membrane affect the net rate of diffusion (all else equal)?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
In the context of diffusion and osmosis, what does passive transport mean?
A
Movement of substances across a membrane that always requires a carrier protein and ATP hydrolysis.
B
Movement of substances across a membrane against their concentration gradient using ATP-powered pumps.
C
Movement of substances across a membrane down their concentration gradient without requiring cellular energy (ATP).
D
Movement of substances only by vesicle-mediated processes such as endocytosis and exocytosis.
Verified step by step guidance1
Understand that passive transport refers to the movement of molecules across a cell membrane without the input of cellular energy (ATP).
Recognize that passive transport occurs down the concentration gradient, meaning substances move from an area of higher concentration to an area of lower concentration.
Note that passive transport can happen through simple diffusion, facilitated diffusion (which may involve carrier proteins or channels), but does not require ATP hydrolysis.
Differentiate passive transport from active transport, which requires energy to move substances against their concentration gradient.
Conclude that the correct definition of passive transport is the movement of substances across a membrane down their concentration gradient without requiring cellular energy (ATP).
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