DSA Osmotic Pressure Flashcards
Diffusion Definition
What are solutes in the body?
Movement of solute across membrane down concentration gradient (High –> Low)
Ions, proteins
Osmosis Definition
When does this occur?
What fluids are involved?
Movement of solvent across membrane
Occurs only if solute can’t move
Intracellular (ICF) & Extracellular (ECF)
Which ion concentrations are greater in the ECF and ICF?
What maintains these differences?
What is the relationship between osmolarity of the ICF and ECF in the body? What does this mean?
Na, Cl, Ca, Bicarbonate higher in ECF
K higher in ICF
ATPases
They are the same, so there is no gradient for osmosis to occur
Osmolarity Equation and what each variable means
What do different g values mean?
Osmolarity = g x [C]
g = dissociation & [C] = molar concentration of substance
g = 1 –> solute doesn’t dissociate
g > 1 –> solute dissociates
Comparing Osmolarities
[Solute] is same in both solutions
[Solute] in one solution < [Solute] in solution it is compared to
[Solute] in one solution > [Solute] in solution it is compared to
Isosmotic
Hypoosmotic
Hyperosmotic
Osmotic Pressure Definition
Estimating Osmotic Pressure Equation
What does the reflection coefficient mean?
Pressure gradient created by difference in solute concentration on either side of semi-permeable membrane
Osmotic Pressure = g[C] x σRT
Reflection Coefficient (σ) = measure of permeability
If σ = 0 –> solute completely permeable and osmosis will not occur
If σ = 1 –> solute completely impermeable and osmosis must occur
What is the average normal osmotic pressure?
What is the normal osmotic pressure range?
290 mOsm
270-300 mOsm
What percentage is Normal saline solution?
Relationship between ICF & ECF?
0.9%
Isosmotic
What is equation for Estimating Osmolality?
Estimated Osmolality = (2x[Na]) + ([glucose]/18) + ([BUN]/2.8)
How does a cell’s volume change in Isosmotic solutions?
How does a cell’s volume change in Hypoosmotic solutions?
How does a cell’s volume change in Hyperosmotic solutions?
No change in cell’s volume because there is no gradient for water
Higher water concentration than in cell so cell will swell/rupture
Osmolarity of solution is greater than cell (lower water concentration) so water moves out of cell and cell shrinks/crenate
How is Tonicity determined?
Isotonic?
Hypotonic?
Hypertonic?
Cell’s response to being put into the solution (not the numbers)
Cell didnt change volume
Cell swelled/lysed as water moved into cell
Cell shrank/crenated as water moved out of cell
