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Active transport
The transport of molecules across a membrane and against their natural flow; mediated by carrier proteins and requiring outside energy.
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Carrier protein
A protein responsible for mediating the active transport of molecules from one side of the lipid bilayer to the other. Transport is carried out by a conformational change that occurs within the protein that forms an opening for specific molecules to pass through.
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Channel protein
A protein responsible for mediating the passive transport of molecules from one side of the lipid bilayer to the other. Transport is carried out by its membrane-spanning hydrophilic structure which, when open, allows molecules to pass through.
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Diffusion
The transport process in which molecules naturally travel from an area of higher concentration to an area of lower concentration.
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Glycocalyx
A layer of carbohydrates that coats the exterior of higher-ordered cells. Functions in protecting the cell from damage.
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Hydrophilic
A polar molecule that selectively associates itself with water through hydrogen bonds.
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Hydrophobic
A nonpolar molecule that does not readily associate with water through hydrogen bonds.
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Integral protein
A membrane protein that cannot be easily removed from the lipid bilayer.
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Ionophore
A class of membrane transport proteins. Small, hydrophobic molecules that increase membrane permeability to certain ions.
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Lipid bilayer
A thin double layer of phospholipid molecules. Provides the structure of a cell membrane. Structure is a result of hydrophobic and hydrophilic forces.
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Lipid-bound protein
Membrane proteins that are located entirely within the lipid bilayer, having no part touching either the inside or outside of the cell.
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Multi-pass protein
Transmembrane proteins that cross the lipid bilayer more than one time.
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Osmosis
The process by which water naturally travels from an area of high concentration to one of lower concentration.
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Passive transport
Transport mediated by channel proteins. The movement of molecules across a membrane according to the natural flow.
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Peripheral protein
A membrane protein that can be easily removed from the lipid bilayer.
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Single-pass protein
A transmembrane protein that only crosses the lipid bilayer one time.
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Transmembrane protein
A membrane protein that spans the lipid bilayer having portions in contact with both the inside and outside of the cell. Area within the lipid bilayer forms an alpha-helix.
