Multiple Choice
In many freshwater protists, which organelle helps prevent the cell from swelling and bursting by collecting and pumping excess water out of the cell?
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9. Transport Across Membranes
Passive Transport: Diffusion and Osmosis
Multiple Choice
In cell biology, what is diffusion?
A
The movement of molecules across a membrane against their concentration gradient using energy from ATP
B
The movement of water across a selectively permeable membrane from lower solute concentration to higher solute concentration
C
The bulk flow of fluid and dissolved substances driven by a pressure gradient through a vessel or tube
D
The net movement of particles from an area of higher concentration to an area of lower concentration due to random thermal motion
Verified step by step guidance1
Understand that diffusion is a fundamental process in cell biology describing how molecules move in their environment.
Recognize that diffusion involves the movement of particles from an area of higher concentration to an area of lower concentration, which is driven by the random thermal motion of molecules.
Note that diffusion does not require energy input (such as ATP) because it is a passive process relying on the natural kinetic energy of molecules.
Differentiate diffusion from other related processes: active transport (which requires energy and moves molecules against their concentration gradient), osmosis (movement of water across a membrane), and bulk flow (movement driven by pressure gradients).
Summarize that diffusion is the net movement of particles down their concentration gradient due to random motion, which helps maintain cellular homeostasis and facilitates the exchange of substances.
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