Multiple Choice
During osmosis in cells, what must water pass through as it moves from an area of lower solute concentration to an area of higher solute concentration?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
In passive transport, what is the primary driving force for diffusion of molecules across space or a membrane?
A
Direct consumption of ATP to pump molecules from low concentration to high concentration
B
Vesicular transport (endocytosis) that encloses molecules in membrane-bound sacs
C
A concentration gradient (net movement from higher concentration to lower concentration due to random thermal motion)
D
A membrane potential that forces all solutes to move only into the cell regardless of concentration
Verified step by step guidance1
Understand that passive transport involves the movement of molecules across a membrane without the input of cellular energy (ATP).
Recall that diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration due to their random thermal motion.
Recognize that the primary driving force for diffusion is the concentration gradient, which is the difference in concentration of molecules across space or a membrane.
Note that active transport, which requires ATP, and vesicular transport, which involves membrane-bound sacs, are different mechanisms and not part of passive transport.
Conclude that in passive transport, molecules move down their concentration gradient, meaning from high to low concentration, driven by random molecular motion without energy input.
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