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Chapter 8
Vocabulary required by my teacher for Chapter 8 in the Campbell Biology Book
33
Biology
11th Grade
04/04/2012

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Term
active transport
Definition
The movement of a substance across a biological membrane against its concentration or electrochemical gradient with the help of energy input and specific transport proteins.
Term
amphipathic molecule
Definition
A molecule that has both a hydrophilic region and a hydrophobic region.
Term
aquaporin
Definition
A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis).
Term
concentration gradient
Definition
An increase or decrease in the density of a chemical substance in an area. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, the ions or other chemical substances involved tend to move from where they are more concentrated to where they are less concentrated.
Term
cotransport
Definition
The coupling of the downhilldiffusion of one substance to the uphilltransport of another against its own concentration gradient.
Term
diffusion
Definition
The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area.
Term
electrochemical gradient
Definition
The diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to move relative to the membrane potential.
Term
electrogenic pump
Definition
An ion transport protein that generates voltage across a membrane.
Term
endocytosis
Definition
The cellular uptake of macromolecules and particulate substances by localized regions of the plasma membrane that surround the substance and pinch off to form an intracellular vesicle.
Term
exocytosis
Definition
The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane.
Term
facilitated diffusion
Definition
The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients.
Term
flaccid
Definition
Limp. A walled cell is flaccid in surroundings where there is no tendency for water to enter.
Term
fluid mosaic model
Definition
The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids.
Term
gated channel
Definition
A protein channel in a cell membrane that opens or closes in response to a particular stimulus.
Term
hypertonic
Definition
In comparing two solutions, referring to the one with a greater solute concentration.
Term
hypotonic
Definition
In comparing two solutions, referring to the one with a lower solute concentration.
Term
integral protein
Definition
Typically a transmembrane protein with hydrophobic regions that completely spans the hydrophobic interior of the membrane.
Term
isotonic
Definition
Having the same solute concentration as another solution.
Term
ligand
Definition
A molecule that binds specifically to a receptor site of another molecule.
Term
membrane potential
Definition
The charge difference between a cell’s cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances.
Term
osmoregulation
Definition
The regulation of solute and water concentrations in body fluids by organisms living in hyperosmotic, hypoosmotic, and terrestrial environments.
Term
osmosis
Definition
The diffusion of water across a selectively permeable membrane.
Term
passive transport
Definition
The diffusion of a substance across a biological membrane.
Term
peripheral protein
Definition
A protein appendage loosely bound to the surface of a membrane and not embedded in the lipid bilayer.
Term
phagocytosis
Definition
A type of endocytosis involving large, particulate substances, accomplished mainly by macrophages, neutrophils, and dendritic cells.
Term
pinocytosis
Definition
A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.
Term
plasmolysis
Definition
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment.
Term
proton pump
Definition
An active transport mechanism in cell membranes that uses ATP to force hydrogen ions out of a cell, generating a membrane potential in the process.
Term
receptor-mediated endocytosis
Definition
The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.
Term
selective permeability
Definition
A property of biological membranes that allows some substances to cross more easily than others.
Term
sodium-potassium pump
Definition
A special transport protein in the plasma membrane of animal cells that transports sodium out of the cell and potassium into the cell against their concentration gradients.
Term
transport protein
Definition
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.
Term
turgid
Definition
Very firm. A walled cell become turgid if it has a greater solute concentration than its surroundings, resulting in entry of water.
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