Multiple Choice
How does increasing diffusion distance affect the rate of diffusion across a membrane (all else being equal)?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
In the context of diffusion and osmosis, what best defines passive transport across a cell membrane?
A
Movement of substances using vesicles to import or export large particles (endocytosis or exocytosis)
B
Movement of substances against their concentration gradient using energy from ATP-driven pumps
C
Movement of substances down their concentration or electrochemical gradient without direct input of cellular energy (ATP)
D
Movement of substances only through membrane proteins and always requiring ATP hydrolysis
Verified step by step guidance1
Understand that passive transport refers to the movement of molecules across a cell membrane without the use of cellular energy (ATP).
Recognize that passive transport occurs down a concentration gradient or electrochemical gradient, meaning substances move from an area of higher concentration to an area of lower concentration.
Differentiate passive transport from active transport, which requires energy to move substances against their concentration gradient.
Note that passive transport can occur through simple diffusion directly across the lipid bilayer or facilitated diffusion via membrane proteins, but it does not require ATP hydrolysis.
Conclude that the best definition of passive transport is the movement of substances down their concentration or electrochemical gradient without direct input of cellular energy.
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