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23 terms

Homeostasis and Cell Transport Chapter 5

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passive transport
the movement of substances across a cell membrane without the use of energy by the cell
diffusion
the movement of particles from regions of higher density to regions of lower density
concentration gradient
a difference in the concentration of a substance across a distance
equilibrium
a state that exists when the concentration of a substance is the same throughout a space
osmosis
diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal
hypotonic
describes a solution whose solute concentration is lower than the solute concentration inside a cell
hypertonic
describes a solution whose solute concentration is higher than the solute concentration inside a cell
isotonic
describes a solution whose solute concentration is equal to the solute concentration inside a cell
contractile vacuole
in protists, an organelle that accumulates water and then releases it periodically to maintain osmotic pressure
turgor pressure
the pressure that is exerted on the inside of cell walls and that is caused by the movement of water into the cell
plasmolysis
the contraction or shrinking of the cell membrane of a plant cell in a hypertonic solution in response to the loss of water by osmosis
cytolysis
the bursting of a cell
facilitated diffusion
the transport of substances through a cell membrane along a concentration gradient with the aid of carrier proteins
carrier protein
a protein that transports substances across a cell membrane.
ion channel
a complex of protein molecules in a cell membrane that form a pore through which ions can pass
active transport
the movement of chemical substances, usually across the cell membrane, against a concentration gradient; requires cells to use energy
sodium potassium pump
a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell
endocytosis
the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell
vesicle
a small cavity or sac that contains materials in a eukaryotic cell; forms when part of the cell membrane surrounds the materials to be taken into the cell or transported within the cell
pinocytosis
a method of active transport across the cell membrane in which the cell takes in extracellular fluids
phagocytosis
the process by which a cell engulfs large particles or whole cells, either as a defense mechanism or as a means to obtain food
phagocyte
a cell that ingests and destroys (digests) foreign matter or microorganisms
exocytosis
the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out