91 terms


plasma membrane
this functions to separate the cell from its surroundings and regulates the transport of material in and out of the cell
small molecules such as ions and mall organic molecules that move across the membrane
the movement of solute across a membrane
passive transport
the movement of solutes across a membrane down the concentration gradient
passive diffusion, ion channels, and facilitated diffusion are all examples of this type of transport
active transport
the movement of solutes across a membrain against the concentration gradient
this kind of transport requires energy
the thermodynamically spontaneous process by which a solute moves across a membrane from a region of higher concentration to one of lower concentration
diffusion always has a [positive/negative] free energy change (delta G)
[true/false] as a solute moves across a membrane down the concentration gradient, energy is made available to do work
delta G = RTln([substrate inside the cell]/[substrate outside the cell])
equation describing the relationship between the concentration gradient of a solute and the delta G of diffusion across a membrane
less than, negative
if there is more substrate present outside the cell than inside, the ratio of [substrate inside]/[substrate outside] will be [greater than/less than] one and delta G of movement of substrate into the cell will be [positive/negative]
equal to, zero, equilibrium,
if there is equal substrate present outside the cell and inside, the ratio of [substrate inside]/[substrate outside] will be [greater than/less than/equal to] one and delta G of movement of substrate into the cell will be [positive/negative/zero], and the system will be at ____
thickness, viscosity, solute
a membrane's ____ and ____ affect the rate of diffusion, as does the permeability of the membrane for the ____
simple diffusion
the unassisted diffusion of a solute across the lipid bilayer of a membrane
down, negative
in order for simple diffusion to occur, the solute must be moving [up/down] the concentration gradient and delta G must be [positive, negative]
size, polarity
the permeability of a membrane to a particular solute is determined by that solute's ____ and ____
nonpolar, hydrophobic
simple diffusion of a solute is more likely if the molecule is [polar/nonpolar] and soluble in the [hydrophilic/hydrophobic] environment of the membrane
more difficult
it is [easier/more difficult] for large solute molecules to move across the membrane than it is for small ones
are not
small organic molecules such as sugar [are/are not] able to diffuse easily across the cell membrane
are, are not
biological membranes [are/are not] permeable to water and [are/are not] permeable to ions and other small polar organic molecules
passive transport of water across a membrane
a compartment with a higher concentration of solute than normal is described as ____
a compartment with a lower concentration of solute than normal is described as ____
when compartments contain equal amounts of solute, they are called ____
are not
lipid bilayers [are/are not] permeable to charged ions
ion channels
protein channels that mediate the transport of ions across a membrane
passive, is not, concentration gradient
ion channels are an example of [active/passive] transport because energy [is/is not] required and the movement of ions is driven by the ____ ____
open, bidirectional
in its simplest form, the ion channel is always [open/closed] and the flow of ions is [not possible/bidirectional]
amino acids
the specificity for certain ions in an ion pore comes from interations between the ion and specific ____ ____ that form a ring around the pore, acting as a selective filter
[true/false] ions pass through ion channels single file
membrane electric potential
the difference in charge across a membrane
the membrane electric potential is measured in ____
electrochemical gradient
the electric potential differences across a membrane combined with the concentration gradient form the ____ ____
delta G = RTln([solute inside the cell]/[solute outside the cell]) + zFVm (where z is the charge of the ion, F is faraday's constant and Vm is the plasma membrane electric potential)
equation relating delta G to the electrochemical gradient
[true/false] the plasma membrane electric potential is a unique property of each membrane
-60, -90, negative
the plasma membrane eletric potential for a typical animal cell is between ____ and ____, indicating an accumulation of [positive/negative] charge inside the cell
for uncharged solutes, the electrochemical gradient is identical to the ____ gradient since the charge z is zero
facilitated diffusion
the protein-mediated transport of solutes across a membrane and down the electrochemical gradient
carrier protein
an integral membrane protein that mediates transport and distinguishes facilitated diffusion
carrier protein
____ ____ mediate transport by binding on one side of the membrane and then undergoing a conformational change that delivers the solute to the other side of the membrane
do not
ion channels [do/do not] directly bind the ion
conformational change
the rate of carrier transport is limited by the rate of the ____ ____ of the protein
false (ions do not directly bind the ion channel in ion channel transport)
[true/false] ion channel transport is limited by the rate of conformational change of the ion channel
electrochemical gradient, exergonic, negative
the direction and likelihood of bother facilitated difusion and ion channel transport are determined by the ____ ____ of the solute and are always [endergonic/exergonic] processes with a [positive/negative] change in delta G
induced fit
the model of solute-induced conformational change of carrier proteins is analogous to the ____ ____ model for the action of enzymes
simple diffusion is analogous to [catalyzed/uncatalyzed] reactions
facilitated diffusion is analogous to [catalyzed/uncatalyzed] reactions
facilitated diffusion is [faster/slower] than simple diffusion across a membrane
[true/false] at high solute concentrations, the carrier protein will be saturated
the Michaelis constant (Km) is the concentration at which the rate of transport equals ____ of Vmax
this constant is a measure of the affinity of the carrier protein for the solute
[true/false] the kinetics of facilitated diffusion are identical to the Michaelis-Menten kinetics of a typical enzyme-catalyzed reaction
red blood cells
the glucose carrier GLUT1 is found on the cell surface of ___ ___ ___
a protein that transports only one solute in one direction
false (it has two: one with the solute binding site facing the inside of the cell, the other facing the outside)
[true/false] the GLUT1 carrier protein has one conformational state
false (it is specific for glucose alone)
[true/false] GLUT1 will transport glucose-6 phosphate
true (rapid phosphorylation of intracellular glucose leads to low intracellular glucose concentration)
[true/false] normally glucose diffusion goes from outside the cell to inside the cell
active transport
the movement of solute against an electrochemical gradient
endergonic (requires coupled input of energy)
active transport is an [endergonic/exergonic] process
active transport carrier proteins
many of these are referred to as pumps because they require energy to move solutes across membranes
a shorter name for an ATP-dependent pump
these transport solutes against their electrochemical gradient by utilizing the free energy associated with ATP hydrolysis
sodium-potassium pump
this pump consumes about one-third of the cell's ATP
this type of ATPase is classified by ATP hydrolysis and subsequent phosphorylation that induces a conformational change that mediates transport of ions against their electrochemical gradient
three, two
during one cycle of pumping, the sodium/potassium pump exports this many ions of sodium and imports this many ions of potassium
after binding sodium ions on the interior of the cell, ATP is hydrolyzed and its phosphate transferred to the ____
exporting, importing
after being phosphorylated, the carrier protein undergoes a conformational change, [importing/exporting] sodium ions
after its initial change, the sodium-potassium pump is dephosphorylated and undergoes an additional conformational change, [importing/exporting] potassium ions
the high concentration of extracellular ____ balances out the high solute concentration (many charged organic molecules) in the cell, thereby maintaining osmotic balance
this type of ATPase utilizes the free energy of ATP hydrolysis to pump hydrogen ions; however, it is not linked to the phosphorylation/dephosphoryltion of a protein
V-type (V, vesicles)
these pumps are typically found in the membranes of vesicles and organelles
V-type pumps are used to move this ion into the lysosome against the electrochemical gradient
this pump runs in the opposite direction of V-type, moving hydrogen ions down the electrochemical gradient driving the synthesis of ATP
ATP-binding cassette (ABC)
this type of ATPase includes a diverse group of proteins that transport a variety of molecules including ions, sugars and peptides. The defective pump that normally moves chloride ions out of the cell in cystic fibrosis patients is thought to be one of these
this kind of pump exists mainly in bacterial cells
this kind of pump is mediated by bacteriorhodopsin; the rhodopsin captures energy from a photon of light and uses it to drive ion movement
light-driven pumps contain a light-absorbing group that, when light is absorbed, induce a conformational change in the rest of the protein that mediate the the transport of these ions
light-driven, F-type
the action of a ____-____ pump creates a steep hydrogen gradient. The free energy associated with this gradient is utilized by an __-____ ATP pump to synthesize ATP
active transport is mediated by carrier proteins that use free energy associated with the electrochemical gradient of one solute to drive the movement of a second coupled solute [down/up] its electrochemical gradient
this carrier protein couples the movement of one particle down its concentration gradient with another particle up its concentration gradient, both in the same direction
this carrier protein couples the movement of one particle down its concentration gradient with another particle up its concentration gradient, each in a different direction
sodium-glucose transporter (cotransporter)
this physiologically important symporter simultaneously transports sodium ions and glucose into the cell
[true/false] most cells take up glucose through facilitated diffusion mediated by a glucose uniporter
epithelial cells lining the ____ take up glucose through active transport via the sodium/glucose symporter
free energy associated with moving ____ ions back into the cell allow active transport of glucose molecules up the concentration gradient into the cell
bicarbonate, chloride
the anion exchange protein transports ____ out of the cell, pwered by the inward movement of ____ down its electrochemical gradient
the anion exchange protein is important in maintaining the cytosolic ____ of cells
interior, exterior
in anion exchange, the antiporter binds bicrabonate on the [interion/exterior] surface of the cell and binds a chloride ion on the [interior/exterior] of the cell. The protein then undergoes a conformational change, delivering bicarbonate to one side and chloride to the other
ion channels
protein-lined pores that allow the rapid, selective, bidirectional movement of ions across the membrane
the direction of transport of ____ is reversible and is determined by the electrochemical gradient of the solute