chapter 4 Flashcards
watery spaces all
the way through the molecule and allow free movement
of water, as well as selected ions or molecules;
channel protein
random molecular move
ment of substances molecule by molecule, either through
intermolecular spaces in the membrane or in combina
tion with a carrier protein.
diffusion
means movement of ions
or other substances across the membrane in combina
tion with a carrier protein in such a way that the car
rier protein causes the substance to move against an
energy gradient, such as from a low-concentration state
to a high-concentration state
active transport
aids passage of the molecules
or ions through the membrane by binding chemically
with them and shuttling them through the membrane in
this form
carrier protein
s have a narrow pore that permits water mol
ecules to diffuse through the membrane in single file
aqauporins
protein channels are distinguished by two important characteristics
1) They are often selectively permeable to certain substances
(2) many of the channels
can be opened or closed by gates that are regulated by
electrical signals (voltage-gated channels) or chemicals
that bind to the channel proteins
chemicals
that bind to the channel proteins
ligand gated channel
consisting of four identical protein subunits surrounding a central pore
tetrameric structures
At the top of the
channel pore that form a narrow selectivity filter.
pore loop
is activated by insulin, which can
increase the rate of facilitated diffusion of glucose as much
as 10-fold to 20-fold in insulin-sensitive tissues. This is the
principal mechanism by which insulin controls glucose
use in the body
GLUT4
attracts the negative ions,
POSITIVE charge
repels the positive ions
negative charge
occurs from left to right.
net diffusion
tends to
move the ions to the left
concentration difference
ends to move ions to the right.
electrical difference
actually means the sum of all the forces of the
different molecules striking a unit surface area at a given
instant.
pressure
process of net movement
of water caused by a concentration difference of water
osmosis
a mixture of permeant water
molecules and nonpermeant sodium and chloride ions
sodium chloride solution
exact amount
of pressure required to stop osmosis
osmotic
pressure of the sodium chloride solution.
concentration of a solution in terms of numbers of particles, the
unit
osmole
is the osmolar con
centration expressed as osmoles per liter of solution rather
than osmoles per kilogram of water
osmolarity
When a
cell membrane moves molecules or ions “uphill” against a
concentration gradient (or “uphill” against an electrical or
pressure gradient)
active transport
, the energy is
derived directly from breakdown of adenosine triphosphate (ATP) or of some other high-energy phosphate
compound.
primary active transport
, the energy is
derived secondarily from energy that has been stored in
the form of ionic concentration
secondary active transport
