4.1 - 4.3 Flashcards
4.1: diffusion 4.2: mediated-transport systems 4.3: osmosis
Molecules of substances within solids, liquids, and gases are in constant motion, and the source of energy causing this motion is ___.
heat
Flux is defined as ___.
the amount of material moving in one direction between two compartments in a given period of time
Which of the following would increase the time it takes for diffusion equilibrium to be reached between a cell’s intracellular fluid and the blood plasma?
Increasing the distance between the cell and the blood stream
Fick’s first law of diffusion states that the rate of diffusion of a substance is proportional to its ___.
concentration gradient
Diffusion of polar molecules into and out of cells and organelles is mainly limited by the ___.
lipid bilayer
T/F: the energy for simple diffusion comes from ATP.
F
To calculate the flux you would need to know the ___ of materials and the unit of time.
amount/quantity
T/F: Diffusion equilibrium between two regions of a solution occurs more rapidly when there is a shorter distance between those regions.
T
Nonpolar molecules diffuse much more rapidly across plasma membranes because these molecules can dissolve in the nonpolar regions of the membrane occupied by the fatty acid chains of the membrane’s ___.
phospholipids
The mathematical formula for Fick’s first law of diffusion is ___.
J=PA(C_o-C_i)
Ions are able to cross the cell membrane by ___.
moving through channel proteins
The lipid bilayer functions as a barrier to the passage of ___-soluble molecules.
water
The resting membrane potential is a result of the inside of a cell membrane having a slight net excess of ___ charges and the outside of a cell having a slight net excess of ___ charges.
negative; positive
The ion’s electrochemical gradient results from the combination of a membrane ___ and a difference in ion ___ across a membrane.
potential; concentration
The lipid bilayer is more permeable to which type(s) of molecule(s)? Select all that apply.
- lipid-soluble
- nonpolar
- hydrophobic
Ion channels can usually be in one of two general states (not including inactivation): the ___ state or the ___ state.
closed; open
Ions move across the cell membrane via ___.
integral membrane proteins
Diffusion of polar molecules into and out of cells and organelles is mainly limited by the ___.
lipid bilayer
Chemical messengers will bind to ___-gated ion channels on the target cell.
ligand
The separation of the electrical charge that exists across plasma membranes of most cells is known as the membrane ___.
potential
Which two factors directly determine the electrochemical gradient acting on a given ion across a cell membrane?
- the membrane potential
- the concentration gradient for the ion
___ are ion channels that open or close in response to changes in the membrane potential.
voltage-gated channels
When ion channels change between their open and closed states we can see changes in the membrane’s ___ to ion’s.
permeability
The passage of amino acids and glucose and the nondiffusional movements of ions across cell membranes are mediated by integral membrane proteins known as ___.
transporters
Which is TRUE about facilitated diffusion across a cell membrane?
The net transport by facilitated diffusion will be zero when concentrations of a substance are equal on the two sides of the membrane.
This type of channel experiences a change in shape when a specific molecule binds to it.
Ligand-gated ion channel
The difference in electrical charge between the inside and outside of a cell membrane is known as the ___.
membrane potential
In active transport, the “active” refers to ___.
the use of energy to power the movement of molecules across a membrane
When membrane potential changes cause movement of charged regions on channel proteins which alter the shape these channels are identified as ___-gated ion channels.
voltage
Integral proteins tend to make excellent __.
transporters, because they span the plasma membrane
Liver cells are able to break down glycogen into glucose, thus causing the intracellular glucose concentration to become higher than the extracellular glucose concentration. What happens to facilitated diffusion of glucose under these conditions?
Facilitated diffusion causes net movement of glucose out of the liver cells.
A specific molecule which binds to a channel protein and either directly or indirectly causes changes to the channel’s shape is called a(n) ___.
ligand
In an individual who is dehydrated, the numbers of aquaporins in the membranes of the kidney epithelial cells will ___; this will permit ___ water to move from the urine that is being formed in the kidney ducts back into the blood
increase; additional
Be able to identify a picture of facilitated diffusion.
x
A solute that cannot cross the cell membrane is called a(n) ___ solute.
nonpenetrating
Active transport is characterized by ___.
- movement of molecules against their concentration gradient
- the requirement for energy
T/F: The permeability of all cells to water is high and constant.
F (number of aquaporins differs in membranes, and in some can be altered by various signals)
Which of the following act as transporters for nutrients to cross the plasma membrane?
integral proteins
