Membrane transport
gradients exist of that are created store the potential energy required to transmit a message or move material between the two compartments
concentration
of substances necessary for optimum function a cell will vary from one substance to the next.
Greater (extracellular)
Na and glucose and Cl.
Greater (intracellular)
K, Mg, PO4 and amino acids.
Diffusion
osmosis- diffusion of solvent. no energy.
Carrier
facilitated diffusion, active transport.. They have to use protein channel to get in and out
Simple diffusion
movement of a solute from an area of high concentration to an area of low concentration. until net diffusion results in an equilibrium or maximum disorganization (highest entropy)
What are factors increase the rate of diffusion?
-the greater concentration gradient
-smaller molecule
-shorter the distnace between two gradients
-greater the surface area between two gradients.
-higher the temperature
Diffusion across the membrane
molecules that are lipid soluble easily follow their concentration gradient and diffuse through cell membrane. (gases, steroid hormones, fatty acids, alcohol)
Osmosis
net diffusion of water across a selectively permeable membrane that separates two solutions that vary in the concentration of at least one of the solutes.
water will move what?
throught across thememrbae in the direction of the higher solute concentration in order to dilute the solute and produce equilibrium between the two solutions.
Water in interstitial fluid will return to the blood plasma, why?
the solute concentration is higher in the blood than in the in interstitium.
how to prevent the movement of water across the membrane?
exert a pressure (osmotic pressure) that offsets the water gradient. Measure assigns a value to a solution based on its ability to draw water.
Molarity
one mole of solute (6.02 X 10 23 molecules) diluted with water up to 1 liter.
Molality
one mole of solute + 1.0 L aka one kg of water
osmolality
the expression for the total molality of a solution and depends on the ratio of the solute to solvent.
Example for osmolality
180g/L of glucose = 1 Osm
180g/L of fructose= 1 Osm
360 g/L of glucose= 2 Osm
180 g/L glucose + 180g/L fructose- 2 Osm.
the ions
affect the Osm of the resulting solution if a substance dissociate in water.
NaCl
dissociate in water to form Na and Cl. It will be 2 Osm
Freezing point
depression of water is used. One mole per liter will decrease the freezing point by -1.86 C.
300 mOSm
normal osmotic concentration of blood plasma
Two commonly used solutions in healthcare
5% dextrose; .3 m and 300 mOsm
-normal saline: .15m NaCl; 300 mOsm.
Ionicity
describes the effect of a solution on the osmotic movement of water.
Isotonic
when the concentration of two solutions is the same
Hypertonic
solution containing a greater number of solutes and will draw water across a membrane. ( RBCs crenate in salt water, RBCs approx .9% NaCl)
Hypotonic
solution containing fewer solutes, thus water moves from this solution, across a membrane and into the compartment with more solutes. (RBCs lyse in pure water)
Carrier transport
Molecules too large, non lipid solube, and polar need help getting in
Faciliaed diffusion
a process of diffusion, a form of passive transport facilitated by transport proteins (transmembrane proteins creating channels )
active transport
Energy-requiring process that moves material across a cell membrane against a concentration difference
Steps of active transport
- the transport molecule binds to the carrier protein
-ATP is converted into ADP and P
-Conformational change in the carrier moves the molecule across the membrane.
-The molecule is released into the opposite compartment and the carrier returns to startin
Na/K pump
Active transporter that moves three Na+ out of a cell and two K+ into the cell against their respective concentration gradients.
primary active transport for pump
move three Na out of the cell. (12% of the ATP used in the body is used by the pump)
Secondary active transport
ATP not directly required. to move two K ions into the cells.
Antiport
A membrane transport process that carries one substance in one direction and another in the opposite direction.
When Na is too high?
the pump will turn on.
membrane potential
exist when there is a charge difference on either side of a plasma membrane. (voltage.)
Concentratoin of a ion
the greater the difference, the greater the potential
Permability
greater the permeability, the more a particular ion will influence the potential.
Fixed anions
nucleic acids, some porein and amino acids, PO4 groups, etc that are contained within the cell and imperable to the plasma membrane.
K+ these cations
are attracted to the fixed anions and are the must permale of the small cations.
What is the intracellular and extracellular for K+?
150 mEq/L---plasma----5.0 mEq/L (extracellular)
Milliequievalent
is the millimolar concentration x valence
Na+
much less permeable to the plasma membrane
intracellular and extracellular for Na.
12 mEq/L---plasma----145 mEq/L
The equilibrium potential
the voltage achieve across a membrane when a single ion is allowed to diffuse to equilibrium. (Nernst equation)
RMP
resting membrane potential, happens when a cell is not producing an impulse.
K, Mg, CA and Cl
all contributed to the RMP in cells
K
most permable
The range of RMP
-65 mv to -85 but neurons are at -70mv