The transport of molecules across a membrane and against their natural flow;
mediated by carrier proteins and requiring outside energy.
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.
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
The transport process in which molecules naturally travel from an area of higher
concentration to an area of lower concentration.
A layer of carbohydrates that coats the exterior of higher-ordered cells.
Functions in protecting the cell from damage.
A polar molecule that selectively associates itself with water through hydrogen
A nonpolar molecule that does not readily associate with water through hydrogen
A membrane protein that cannot be easily removed from the lipid bilayer.
A class of membrane transport proteins. Small, hydrophobic molecules that
increase membrane permeability to certain ions.
A thin double layer of phospholipid molecules. Provides the structure of a cell
membrane. Structure is a result of hydrophobic and hydrophilic forces.
Membrane proteins that are located entirely within the lipid bilayer, having no
part touching either the inside or outside of the cell.
Transmembrane proteins that cross the lipid bilayer more than one time.
The process by which water naturally travels from an area of high concentration
to one of lower concentration.
Transport mediated by channel proteins. The movement of molecules across a
membrane according to the natural flow.
A membrane protein that can be easily removed from the lipid bilayer.
A transmembrane protein that only crosses the lipid bilayer one time.
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.