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60 Cards in this Set

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Resting potential can be considered the _________ of a tug-of-war between two ionic gradients
outcome
The strength of the two contestants in this "tug of war" between two gradients is determined by what 2 factors?
concentration gradient
relative permeability
The plasma membrance is about ____ to ____ times more permeable to K+ than to Na+
50 to 75
The concentration gradient for K+ is ____ times that of Na+ . So who would be the winner in the tug of war?
3
K+ (on both..permeability and gradient)
The resting potential is determined by the magnitude of the _______ ______ of Na+ and K+ weighted by their __________.
concentration gradients
permeabilities
Na+ and K+ are out of equilibrium (cellular). K+ has the driving force that would cause it to what?
Leak out of the cell
Na+ has a net driving force that would cause it to what?
diffuse into the cell
Both of these leakage processes must be countered continously how?
Cellular precess that spends energy to drive Na+ against its gradient out of the cell and bring in K+ against its gradient into the cell.
What is this cellular mechanism that accomplishes the above (Na+ and K+ exchange) called?
Na and K+ pump.
In contrast to Na+ and K+ most excitable cells do not __________transport Cl~
actively
Law of electroneutrality
never staying more than a short distance away from a corresponding counterion.
Three major mechanisms by which solutes can move between the interior and exterior of cells
diffusion
carrier-mediated transport
endocytosis and exocytosis
In order to cross between extracellular fluid and cytoplasm, diffusing substances must what?
pass thru the plasma membrane that defines the outer boundary of each individual cell
This can happen if the membrane is _________ to the diffusing substance.
Permeable
Permeability to a particular substance is the property of the ___________.
membrane
Permeant substance
a substance to which the membrane is permeable to.
Permeant substances are generally eith very ______molecules (like water) or substances that can dissolve in lipids.
small
There are a large number of physilogically important substances that can permeate plasma membrane even though they are large and lipid insoluable. How?
Due to the presence in plasma membranes of membrane-spanning TRANSPORT PROTEINS that provide alternative routes through the membrane.
Transport proteins can take two forms
channels
carriers
Channels
barrel shaped pores that enclose a small water filled passage thru which solutes diffuse as if in free solution.
Frequently have gates that open and close
What causes these gates in channels to open and close?
Sometimes it happens spontaneously, but a great many channels are opened or closed by external influences.
Voltaged gated
respond to changes in membrane potential
ligand gated
respond to binding of messengers substance from inside or outside the cell.
Channel mediated movement is diffusion like in that the driving force is proveded by the solute's ________ ________ so this is a passive process.
concentration gradient
Generally channels exhibit at least some degree of __________, so that it is possible to speak of Na+ channels, K+ channels, Ca++ channels and Cl~ channels
selectivity
_________ are proteins that actually bind individual molecules on one side of the membrane and release the solute on the opposite side of the membrane.
Carriers
when multiple solutes of different types need to bind to the carrer before all are translocated, this is called what?
cotransport or symport
2 destinctions between channel mediated transport and carrier mediated transport.
channels typically mediate a much higher rate of movement than do individual carriers.

Movement of solutes thru the membrane by way of carrier proteins may be active, whereas cahnnels can never mediate active transport.
________ _______ involves the expenditure of extra reserves and can result in net movement of solute uphill against a concentration gradient.
Active transport
In PRIMARY ACTIVE TRANSPORT, the carrier derives its energy from where?
ATP adenosine triphosphate
ATP and such carrier proteins are members of a large family of _______ _____.
ATPase Enzymes
The most common form of transport ATPase is what?
Na+/K+ pump which is found in virtually all cells.
Explain how the Na+ and K+ pump works.
In each of its cycles the Na+/K+ splits 1 ATP and mediates the ejection of 3 Na+ form the cell in exhange for 2 K+ moved from outside to in.
Since the cytoplasm has a higher concentration of K+ than the extracellular fluid, the situation is the ________ for Na+
reverse
Secondary active transports are not driven by ATP but by what?
a transmembrane gradient of some other solute
___________is the process of cellular uptake in which a small region of the plasma membrane is first indented to form a pocket and then is pinched off to form a packet of plasma membrane containing anything that was within the pocket when it formed.
Endocytosis
endocytotic vesicle
packet that is formed in plasma membrane containing anything that was within the pocket when if formed. (during endocytosis)
If the pocket that is formed during endocytosis include extracellular fluid with water and solutes, the uptake of such fluid is called what?
pinocytosis (literally cell drinking)
Alternately the point of endocytosis could be to move to the cellular interior certain membrane proteins, termed ___________, together with specific extracellular substances that have become bound to the receptors. This process is called what?
receptors
receptor mediated endocytosis
Some cells of the immune system can engulf whole bacteria or particles of foreign material. What is this process called?
phagocytosis (literally cell eating) Normally these are digested within the cell (bacteria)
__________ is a process in which intracellular vesicles fuse with the plasma membrance and release their contents to the exterior
exocytosis
What are important functions of exocytosis?
mechanism of secretion of large quantities of substances that could not permeate the plasma membrane by themselves.

Important in endocrine secretion of protein and peptide hormones, secretion of proteins that must function in the extracellular environment, and in synaptic transmission of chemical signals etween neurons or between neurons and muscle cells.
__________ is diffusive movement of water down a water concentration gradient.
Osmosis
Particles in solution dilute the concentration of the water that contains them, so the _________ the solute concentration of a solutin, the _____ its water concentration.
greater
lower
In the presence of a gradient of water concentration, net movement of water will occur in the direction of________ solute concentration (=______ water concentration)
higher
lower
Throughout most organs and tissues, the osmotic concentration of the cytoplasm is approx _______ and the exteacellular fluid has the same concentration.
300 mOsmoles/L
Solutions that have the above (300 mOsmoles/L) are said to be what?
Isotonic
A solution that contains a lower concentration of impermeate solute than normal cytoplasm ( and therefore a higher osmotic strength) and causes cells placed in it to swell
hypotonic
solution that contains a higher impermeant solute concentration and causes cells to shrink.
hypertonic
The solutions for the delivery of IV drugs must be ________.
isotonic
extracellular fluid
all fluids ouside cells
extracellular fluids has 2 main components
interstitial fluid: immediately surrounds cells and tissues

blood plasma: fluid component of the blood
Extracellular fluid is threatened by all unregulated losses or gains of solute or water. give ex
evaporation of water from body surface, respiratory system, sweating, gain of solute from diet and loss of feces.
ECF composition and volume are protected by a network of homeostatic processes that involve what and how does it regulate?
The kidney, which regulates solute and water losses from the body and the brain which regulates salt appetite and thirst.
For the purpose of understanding osmotic homeostasis of body fluid, you could think of the cytoplasm of all cells as belonging to a single what?
All solutions outside the cells belongs to the ________.
intracellular compartment
extracellular compartment
There two compartment are separated by a ______ _______ barrier called the plasma membrane.
water permeable
A homeostatic challenge that adds additonal impermeant solute to the ECF without changing the total water content of the body will do what?
drive movement of water from the intracellular compartment to the extracellular compartment until the osmotic concentrations of bother compartment are again equal, but higher than normal.
Likewise a challenge that decreases total extracellular solute will result in what?
In somotic flow of water into the cells until osmotic concentration of the 2 compartments becomes equal, but lower than normal.
In case of a homestatic challenge that adds addition impermeant solute to ECF with changing the total water content of the body...this is called a _______challenge.
hypertonic challenge. (the cells have shrunk )

Corrected only by correcting the ECF composition
As in case where challenge that decreases total extacellular solute is called __________ challenge.
hypotonic challenge (the cells have swelled)

Corrected only by correcting the ECF composition