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35 Cards in this Set

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  • Back
What are the factors acting to produce molecular motion?

The existance of a conc. gradient for a given type of a molecule across a cell membrane

Molecules always move from area of high concentration to areas of lower conc.

The greater the conc., the more the molecules will move.
1. Ions are affected by differences in charge found inside & outside of cell membranes.
2. Is in fact, an unequal distribution of charged particles across a cells membrane
A. more - ions inside a cell
B. more + ions outside a cell
3. Creates an electrical charge differences across a cell membrane, measured in millivolts
A. called the Membrane Potential, often about 70 millivolts inside composed to outside
4. Charge difference can affect ion movement across membranes.
a. like charges repel
b. unlike charges attract
The combined effects of the chemical & electrical forces
a. may be added to ↑ the effect
b. may be in opposition to eachother
c. ions are effected by both
d. uncharged molecules not effected by electrical forces
Simple diffusion
The movement of molecules from area of high conc of 1 type of molecule to areas of lower conc of that molecule

a. due to thermal energy within the molecules
1. ALL molecules are in motion
2. Motion is random (molecular collisions occur)
b. is a PASSIVE process
c. can occur across the lipid bilayer ov a cell membrane (fat soluble molecules- triglycerides, steroid, ecosenoids...)
a. lipid solubility of a substance *** most important ***
b. molecular size - ↑ size will decrease diffusion
c. Temp - ↑ temp will increase diffusion
What are the factors affecting membrane permeability? (3)
Facilited Diffusion
Diffusion of molecules across cell membrane using a transcript protein (carrier or channel)
Is necessary because many molecules needed by cells are not lipid soluble (need some way to cross cell membrane)
Is a PASSIVE process
Channels are important is this diffusion
a protein that extends from opening extending through it (AKA pores)
A. may act as a pore
B. may have binding sites for particular molecules (usually ions) (specificity in channels)
C. will move ions down electrochemical gradient
Cell membrane transport
Molecules must be able to pass into or out of cells through the cell membrane
Passive Transport
Molecular motion across a cell membrane not requiring cell energy
motion is due to the kinetic (thermal) energy of the molecules.
Active transport
Molecular motion across a cell membrane that requires the use of cell energy (ATP) and transport proteins often called carriers or pumps.
Active transport
use CARRIER PROTEIN to move molecules AGAINST a conc. grad. or electrochemical grad.

requires the use of ATP directly or indirectly to produce movement
What are the types of active transport?

primary active transport
use of membrane proteins to act as ATPase (energy source) and use transport molecule (carrier)

ex. sodium/potassium pump in almost all cells.
act to create & maintain an electrochemical gradient across cell membranes
secondary active transport
The coupling of 2 transport processes together

a. 1 process moves molecules down their conc. grad. Releasing energy and allowing a 2nd process to move other molecules against their conc grad

*ATP is NOT used
*energy source (direct) sodium/potassium pump
______ lowers blood glucose by increasing the transport of glucose

makes more carriers
Diffusion of WATER across a cell membrane

1. Always passive
2. Driven by the conc grad for water (Water conc in a solution is affected by the presence of solutes in that solution.

Higher the solute conc the lower the water conc, visa versa
A measure of the total solute conc (# of particles) of a solution
1 mole of any solute in a liter of water has a conc of 1 osmole
Millisole - 1/1000 of an osmole

Ex. 300 mOsm = 300/1000 of an osmole

Solutes that ionize have TWICE the osmotic effect of other solutes because they dissociate (break apart) when in water producing TWICE the # of particles in the water.
Osmotic Pressure
Pressure that is necessary to STOP water solution across a membrane into a solution containing non-diffusable solutes

1. increase amount of solute will ↑ _______ pressure
2. _______ pressure is actually a measure of the tendency for water to diffuse into a solution
3. The higher the osmotic pressure of a solution, the greater will be the tendency for water to diffuse into that solution.
a transmembrane protein that transports molecules via a passageway or PORE that extends from one side of the membrane to the other.

Specificity to substances that enter
From electrochemical gradient of another solute
Where does Secondary active transport get its energy?
ATP or other chemical energy source
Where does Primary active transport get its energy?
a transmembrane protein that binds molecules on one side of a membrane and transports them to the other side by means of a conformational change, or a change in shape.
The volume of a cell is determined by the _______ of the solution surrounding it, which depends on the solute conc and the permeability of the membrane to the solutes that are present.
a solution that will not alter cell volume
a solution that draws water out of a cell causing the cell to shrink
a solution with a lower osmolarity than another
uptake of material into a cell via vesicles that pinch off from the plasma membrane

enable macromolecules and larger particles to enter cells.
transport of materail out of a cell via vesicles that fuse with the plasma membrane

involved in the cellular secretion of hydrophilic molecules
"cell eating"

The engulfing of extracellular materials or pathogens

the movement of extracellular materials into the cytoplasm by pinching the plasma membrane into a membranous vesicle.

common is WBC's
"cell drinking"

The introduction of fluids into the cytoplasm by enclosing them in membranous vesicles at the cell surface

Nonspecific process
Receptor-mediated endocytosis
Specific process

Receptor proteins on the plasma membrane bind specific molecules, triggering endocytosis.

Plasma membrane then indents around molecules, forming a vesicle that pinches off of the plasma membrane and enters the cell.
Coated pit
an indentation of the plasma membrane that eventually forms an endocytotic vesicle

Coated on its inner surface by specific proteins.
the # of molecules crossing a membrane in a given length of time

A measure of the rate at which a substance is being transported
proteins that actively transport molecules across a membrane