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Passive Transport

The movement of materials through a cell membrane without using energy.


Process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated.

Concentration Gradient

The difference in the concentration of molecules across a distance.


When the concentration of a solute is the same throughout a solution.


The diffusion of water across a selectively permeable membrane.


Describes a solution whose solute concentration is lower than the solute concentration inside a cell.


When comparing two solutions, the solution with the greater concentration of solutes.


When the concentration of two solutions is the same.

Contractile Vacuoles

Organelles that remove water.

Turgor Pressure

The pressure that water molecules exert against the cell wall.


Collapse of a walled cell's cytoplasm due to a lack of water.


The bursting of cells.

Facilitated Diffusion

The transport of substances through a cell membrane along a concentration gradient with the aid of carrier proteins.

Carrier Proteins

A protein that transports substances across a cell membrane.

Ion Channels

Another type of passive transport that involves membrane proteins.


A membrane bound sac that contains materials involved in transport of the cell.


A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.


The process by which a cell engulfs large particles or whole cells, either as a defense mechanism or as a means to obtain food.


Cells that use phagocytosis to engulf foreign organisms.


The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.

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