Lecture 7 Flashcards
(23 cards)
active transport
Movement of a substance across a cell membrane. Requires energy.
amphipathic molecule
Having both
a hydrophilic region and a hydrophobic
region.
concentration gradient
A region along
which the density of a chemical substance
increases or decreases.
cotransport
The coupling of the ?downhill?
diffusion of one substance to the ?uphill?
transport of another against its own concentration
gradient.
diffusion
The random thermal motion of particles
of liquids, gases, or solids. In the presence
of a concentration or electrochemical
gradient, diffusion results in the net movement
of a substance from a region where it is more concentrated to a region where it is
less concentrated.
endocytosis
Cellular uptake
of biological molecules and particulate
matter via formation of vesicles from the
plasma membrane.
exocytosis
The cellular secretion
of biological molecules by the fusion
of vesicles containing them with the plasma
membrane.
facilitated diffusion
The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.
gated channel
A transmembrane protein
channel that opens or closes in response to a
particular stimulus.
hypertonic solution
Referring to a solution that, when
surrounding a cell, will cause the cell to lose
water.
hypotonic solution
Referring to a solution that, when
surrounding a cell, will cause the cell to take
up water.
integral protein
A transmembrane protein
with hydrophobic regions that extend into
and often completely span the hydrophobic
interior of the membrane and with hydrophilic
regions in contact with the aqueous
solution on one or both sides of the membrane
(or lining the channel in the case of a
channel protein).
isotonic solutions
Referring to a solution
that, when surrounding a cell, causes no net
movement of water into or out of the cell.
ligand
A molecule that binds specifically
to another molecule, usually a larger
one.
osmosis
The diffusion of free water
molecules across a selectively permeable
membrane.
passive transport
The diffusion of a substance
across a biological membrane with
no expenditure of energy.
peripheral protein
A protein loosely bound
to the surface of a membrane or to part of
an integral protein and not embedded in the
lipid bilayer.
phagocytosis
A type of
endocytosis in which large particulate substances
or small organisms are taken up by
a cell. It is carried out by some protists and
by certain immune cells of animals (in mammals,
mainly macrophages, neutrophils, and
dendritic cells).
pinocytosis
A type of endocytosis
in which the cell ingests extracellular
fluid and its dissolved solutes.
receptor?mediated endocytosis
The movement of specific molecules
into a cell by the inward budding of
vesicles containing proteins with receptor
sites specific to the molecules being taken
in; enables a cell to acquire bulk quantities of
specific substances.
selective permeability
A property of biological
membranes that allows them to regulate
the passage of substances across them.
sodium?potassium pump
A transport protein
in the plasma membrane of animal cells
that actively transports sodium out of the
cell and potassium into the cell.
transport protein
A transmembrane protein
that helps a certain substance or class
of closely related substances to cross the
membrane.
