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79 terms

Physiology - Membrane, Diffusion II (Lec3)

exchange materials
The cells in your body need to ___ ___ with their immediate environment
passively, actively
Molecules can pass through membranes ___ or ___ (with or without energy required)
thermal motion
Molecules of any substance (solid, liquid or gas) are in a continuous state of movement or vibration, called ___ __.
The avg speed of "thermal motion" also depends upon the ___ of the molecule (water moves faster than glucose)
The warmer a substance is the ___ its molecules move.
In solutions, rapidly moving molecules cannot travel very far before colliding with other molecules (millions of ___ every second)
Each collision ____ the direction of the molecule's movement.
diffusion, passive
The movement of molecules from one location to another as a result of their own thermal motion is know as ___. It is also what kind of "mechanism"...passive or active?
higher, lower
Constant random motion of molecules = areas of ____ concentrations to regions of ____ concentrations until a uniform concentration.
The amount of material crossing a surface in a unit of time is called ___.
The one-way flux of glucose from compartment 1 to compartment 2 depends on the ___ of glucose in comparment 1.
move back
After a short time, glucose molecules that have entered compartment 2 will randomly ___ ___ into compartment 1.
net flux
What accounts for solute movements in both directions? __ __
difference, one way
Net flux in diffusion is the ____ between the two ___-___ fluxes.
diffusion equilibrium
When the difference between the two one-way fluxes is zero (net-flux is zero) the system has now reacheed ____ ____.
The greater the difference between the two one-way fluxes the greater the concentration ____.
do not
Most polar molecules ___ ___ diffuse into cells, or very slowly.
non polar
____-____ molecules diffuse very well across membranes.
Ions (Na+, K+, Cl-) diffuse across plasma membranes very fast even though they are very ___
integral protein
Ions pass through the cell membrane through the ___ ___ (tunnel's) that are in the membrane
Proteins form _____ for the ions to flow through.
The small size of the channels allows for some ions to come through but not larger, ____ molecules to pass.
size, charged
Ion channels are selective to the ion they allow in because of their ____ selectivity and the __ surface that can either attract or repel ions.
membrane potential
The opposite charges on each side of the membrane is called ____ ____
positive, negative
Even if there is no concentration difference of ions there is still a net movement of ____ ions into and ____ ions out of the cell
concentration, membrane potential
The two driving forces of ion movement (____ and ____ ____) are known as electrochemical gradient.
electrochemical gradient
The two diriving forces of ion movement (concentration and membrane potential) are known as ____.
The net flux always proceeds from regions of higher concentration to regions of lower concentration. This is known as __ __ diffusion
mass, medium, surface, temperature
The magnitude of the net flux depends on several additional factors, regardless of concentration difference: name the four
higher, greater
Diffusion factor: the ___ the temperature, the greater the speed of the molecular movement and the ___ the net flux.
mass, smaller
Diffusion factor: ____ of the molecule - larger molecules (i.e. proteins) have a greater mass and lower speed = ____ net flux
faster, greater
Diffusion factor: mass of the molecule - smaller molecules (i.e. glucose) have a smaller mass and ____ speed = ____ net flux.
The greater the surface area between two regions, the greater the space availabe for diffusion = ____ the net flux
Diffusion factor: the ____ through which the molecules are moving (gas -vs- a liquid -vs- a solid)
The medium through which the molecules are moving ---- molecues diffuse ____ in air than in water because collisions are less in a gas.
The major factor limiting diffusion across a membrane is the ____ interior of its lipid bilayer.
Facilitated diffusion uses a ___ to move solute "downhill" from a higher to a lower concentration across a membrane.
active transport
____ ____ uses a transporter coupled to an energy source to move solute "uphill" across a membrane - against its electrochemical gradient.
With facilitated diffusion the transported solute binds to a specific site on a _____ protein.
____ diffusion uses a transporter to move solute "downhill" from a higher to a lower concentration across a membrane.
Facilitated diffusion: protein undergoes _____ change then exposes binding site to the other side of the membrane.
ions, molecules
Faciliated diffusion has a limit as to how many ____ and ____ can pass because the transporter must change its shape for each.
Integral membrane proteins are known as ____.
Ion channels can move several thousand times more ions than transporters because there is no change in ____ (shape)
facilitated, active
Two types of mediated-transport exist: ____ diffusion and ____ transport
In both simple and facilitated diffusion, solutes move in the direction predicted by the ____ gradient. (downhill)
Active transport uses ____ to move a substance uphill (low to high) across a membrane ---- that is, against the substance's electrochemical gradient.
saturated, transporters, conformational
Three factors determine the magnitude of solute flux through a membrane with mediated-transport: 1) How __ the binding sites are. 2) number of __. 3) rate at which the __ changes occur in the transport protein
Active transport moves a substance ____ the substance's electrochemical gradient. (low to high)
Active transport: Requires binding of a substance to the ____ in the membrane ("pumps")
Active transport: Because these transporters move the substance uphill, they are often referred to as ____
Moving substances "up-hill", and keeping things that way, requires constant input of ____ into active transport process.
higher, lower
Active transport: must be coupled with simultaneous flow of some energy source from a ____ energy level to a ____ energy level.
primary active, secondary active
The two means of coupling an energy flow to transporters are: ___ __ transport and ___ __ transports.
Transporter (ATPase) catalyzes the breakdown of ATP ---> phosphorylating itself. This is what kind of active transport?
Transport protein couples the flow of one substance to that of another. This is known as ____ active transport.
Secondary active transport: one substance moves ____ down its electrochemical gradient, releasing energy that is then used by hitch-hiker
Secondary active transport: The released energy is then used to drive movement of other substance (hitch-hiker) up its ____ gradient
low, high
Secondary active transport: hitching a ride while moving ___ to ___ (up it's electrochemical gradient)
The net diffusion of water across a membrane is called ____.
The total solute concentration of a solution is called its ____
A family of membrane proteins known as ____ that form channels through which water can diffuse.
Water diffuses across all membranes very rapidly even though it's a ____ (unequal sharing of electrons --> so it has a positive end and a negative end) molecule.
semipermeable, compartments
____ membrane - permeable to water but not to solutes. It creates pressure between __ (inside and outside the cell)
_____ pressure - the pressure that must be applied to the "solution" to prevent the net flow of water into the solution.
____ solution - inside and outside are the same, no change in the cell will occur.
_____ (cell expands) - has "less" solute (ex.- from drinking too much water)
_____ (cell shrinks) - has "more" solute (like during dehydration)
cell membrane
Molecules can enter cells without passing "through" the ____ ____
___ - Regions of the plasma membrane fold into the cell forming pockets that enclose extracellular fluid, becoming intracellular, membrane-bound vesicles
__ - Membrane-bound vesicles in the cytoplasm fuse with the cell membrane and release their contents into the extracellular fluid.
Molecules passing through membranes "passively" do not need __ to move (like coasting down a hill in a car)
Molecules passing through membranes "actively" need __ to move (like gas in a car to get up a hill)
non-polar, non-polar, diffusing
Polar and non-polar things do not mix, like oil & water. Center of the membrane is __-__. So, __-__ molecules have no problem __ across the membrane.
affinity, binding, protein, transporter, phosphate, affinity, solute, phosphorylation
Primary active transport - Phosphorylation of the transporter protein changes the __ (attraction) of the transporters solute to the __ site. Once the solute binds to the site it causes a conformation change in the __ (__). Once the transporter has a conformation change, it causes the __ group to be removed --> causing the __ of the binding site to break down --> release of the transported __. The low affinity site returns to it's original side, it is in a conformation that once again permits ___, and the cycle repeats.
Primary active transport - transporter (ATPase) catalyzes the breakdown of ATP --> __ itself.
One of the most crucial examples of active transport in the body (present in nearly every cell) is the __-__ pump
inside, outside
The sodium-potassium pump is responsible for high K+ __ the cell and high Na+ __ the cell.
For each ATP that is hydrolized (used), __ Na+ are moved out of the cell and __ K+ are moved in to the cell.