2010_ch 5: Homeostasis & Cell Transport

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ch 5 Modern Biology, 2009

passive transport

the movement of substances across a cell membrane without the use of energy by the cell; includes diffusion, osmosis, and facilitated diffusion

diffusion

the movement of particles from regions of higher density to regions of lower density (down a concentration gradient); does not require cellular energy & is therefore a form of passive transport

concentration gradient

a difference in the concentration of a substance across a distance

equilibrium

in biology, a state that exists when the concentration of a substance is the same throughout a space; materials will continue to move across a cell membrane, at an equal rate in both directions

osmosis

the diffusion of water across a cell membrane, from a region of high WATER concentration (low solute concentration) to a region of low WATER concentration (high solute concentration)

hypotonic

describes a solution in which the solute concentration is lower than the solute concentration inside a cell; water will move out of the hypotonic solution and into the cell

hypertonic

describes a solution in which the solute concentration is higher than the solute concentration inside a cell; water will move out of the cell and into the concentrated solution

isotonic

describes a solution whose concentration is equal to the solute concentration inside a cell; water will move at the same rate into and out of the cell

contractile vacuole

in freshwater protists, an organelle that gathers water from within the cell and then pumps it out of the cell to maintain osmotic pressure (so the cell does not burst)

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 cell in a hypertonic solution in response to the loss of water by osmosis

cytolysis

the bursting of a cell as water moves into the cell and stretches the cell membrane in a hypotonic solution

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 across the cell membrane against a concentration gradient; requires cells to use energy; includes sodium-potassium pump, proton pumps, endocytosis, and exocytosis

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 membranes surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell; requires cellular energy and is therefore a form of active transport

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 form of endocytosis in which the cell takes in extracellular fluids

phagocytosis

a form of endocytosis in 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; includes antibodies in your immune system

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; requires cellular energy and is therefore a form of active transport

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