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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.

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