# Shared Flashcard Set

## Details

"Membrane Transport"
9/10/07--for quiz 1
15
Physiology
Not Applicable
09/12/2007

## Additional Physiology Flashcards

Term
 What is volume and composition of body fluids?
Definition
 Total Body Water (TBW)50-70% body weightI) Intracellular fluid (ICF) ~2/3rds TBW -25 LII) Extracellular fluid~1/3rd TBW a) Interstitial Fluid-13 Lb) Plasma-3 L III) Transcellular--1L
Term
 What is difference b/w moles, osmoles, equivalents, and pX+?
Definition
 1) Mole: 6 X 1023 molecules of a substance2) Equivalent: amount of charged (ionized) solute and is the # of moles of solute multiplied by its valence. Example: 1 mole of CaCl2 dissociates into two equivalents of calcium and two equivalents of chloride. (Ca = 2+ , Cl = 1-)3) Osmole: number of particles into which a solute dissociates Example: 1 mmol/L of CaCl2 dissociates into 3 mOsm/L. (1 Ca particle, 2 Cl particles)
Term
 What is Fick's Law of Diffusion?
Definition
 J=-DA(dc/dx) J = Net rate of diffusion D = Diffusion coefficient A = Area of the plane diffusing across dc/dx = Concentration gradient
Term
 What is Einstein relation for calculating diffusion times?
Definition
 (Δx2)=2Dt Δx = change in diffusion distance Dt = change in time
Term
 What is the main idea behind Stokes-Einstein relation?
Definition
 D= kT/ 6πrη D = Diffusion coefficientK = Boltzmann’s constantT = absolute temperature (in Kelvins)R = molecular radiusη = viscosity of medium
Term
 How can various factors influence diffusion coefficient in the Stokes-Einstein relation?
Definition
 Parameters that influence diffusion coefficient:1) Viscosity of medium (intrinsic property)--syrup (higher viscosity, slower diffusion) --water (lower viscosity, more rapid diffusion) 2)Temperature- ↑ Temp = ↑ diffusion 3) Radius of molecule: ↑ radius = ↓ diffusion
Term
 What is osmosis and osmotic pressure?
Definition
 Osmosis: flow of water across a semipermeable membrane due to a difference in solute concentration.Osmotic pressure: pressure required to prevent the flow of water
Term
 What is Van't Hoff's Law? How can it be used to calculate osmotic pressure?
Definition
 Van’t Hoff’s Law: ∏= g C σ RTΠ = osmotic pressure (atm) g = particles per mole in solution (Osm/L) C = concentration (mmol/L) σ = reflection coefficient (0 to 1; 1 being impermeable, 0 is permeable) R = gas constant T = absolute temperature
Term
 What is difference between permeant and impermeant solutes? How can this lead to different definitions of osmolarity and tonicity?
Definition
 Permeant solute: moves freely across semipermeable membraneImpermeant solute: do not passively diffuse into or out of semipermeable membrane, usually creates hypertonic soln.osmolarity--(don't memorize this, but is= gC, where g=number of particles in solution and C=concentration of particles--it is important whether molecule DISSOCIATES in solution) measures number of dissolved particles in water. isoosmotic--same number of dissolved particlestonicity--measures tendancy of solution to resist expansion of intracellular volumeisotonic--no water movement. tonicity--describes
Term
 How do permeant v. impermeant solutes influence osmolarity and tonicity?
Definition
 Osmolarity: measures effective gradient for water assuming all the solute is completely impermeant (measured per L). Ex: 300 millimolar solution of glucose (1 osmole), a 300 millimolar solution of urea (1 osmole), and a 150 millimolar solution of NaCl (2 osmoles) each have the same osmolarity.Tonicity: describes the tendency of a solution to resist expansion of the intracellular volume. Sometimes referred to as “effective” osmolarity. Operational Definition Two solutions are isosmotic when they have the same number of dissolved particles, regardless of how much water would flow across a given membrane barrier. In contrast, two solutions are isotonic when they would cause no water movement across a membrane barrier, regardless of how many particles are dissolved.In the example given above, a 150 mM NaCl solution would be isosmotic to the inside of a cell, and it would also be isotonic--the cell would not swell or shrink when placed in this solution (cell is normally ~300 mM). On the other hand, a 300 mM urea solution, while still isosmotic would cause the cell to swell and burst (due to its permeability). This isosmotic urea solution is not isotonic. Instead it has a lower tonicity (hypotonic).If different osmotic pressures, then not isotonic. If different reflection coefficients (σ) or “permeability”, not isotonic.
Term
 What is Gibbs-Donnan equilibrium?
Definition
 Definition: Plasma contains impermeable negative charges that leads to a redistribution of permeant anions (Cl-) and cations (Na+) [Na+]o/[Na+]i= [Cl -]i/[Cl -]o-->Na is higher outside cell, Cl is higher inside cell--so [Na]o/[Na]i=[Ca]i/[Ca]o
Term
 What is anion gap? How is it calculated?
Definition
 Anion Gapplasma = [Na+]plasma - ([Cl-]plasma + [HCO3-]plasma) Useful for diagnosis of acid-base disorders. The anion gap is based upon the principle of electroneutrality: for any body fluid compartment (ie plasma), the concentrations of cations and anions must equal.
Term
 What is facilitated diffusion? What is good example of facilitated diffusion?
Definition
 -->A process whereby a substance passes through the membrane with the aid of an integral membrane protein--Substances move down their electrochemical gradient --Saturation, stereospecificity, competition are all relevant--Does not require energy (ATP) --Ex: ion channels, transporter (GLUT 4 for D-glucose
Term
 What is primary active transport? What is a good example of this?
Definition
 -->Movement of a substance uphill (against conc gradient); the energy source is directly coupled to the transport process. --Requires ATP--Ex: Na-K pump, Ca ATPase
Term
 What is secondary active transport? What is a good example of this?
Definition
 -->transport of two or more solutes is coupled--One molecule moves down conc gradient, provides energy for uphill movement of other molecule--ATP supplied “indirectly” via primary molecule--If uphill molecule moves in same direction as Na+ = cotransport or symport-Ex: Na-glucose cotransport--If uphill molecule moves in opposite direction as Na+ = countertransport-Ex: Ca-Na exchange in muscle
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