transport of water

Question 1

Two pathway exist for rapid flux of water

Answer 1

10% via interlipid pathway (via h2o concentration gradient

90% transmembrane flux occurs thru aquaporins (selective integral protein structures) through facilitated diffusion

Question 2

Definition of osmosis

Answer 2

displacement of volume due to the net movement of water down its concentration gradient across a semi permeable membrane
(needs to be impermeable to one solute to be semipermeable)

Impermeable solute particles are referred as osmolytes (and are osmotically active)

Osmotic pressure: counter hydrostatic pressure required to prevent a change in compartment volume (a colligative properties) depends upon the relative number of particles of solute and solvent in solution and degree of dissociation of the solute particles from each other
(osmotic difference)=number of dissociated particles per molecule* concentration difference* osmotic coefficient (how easily it dissociates)

Ideal semi permeable conditions: solute is completely dilute, absolutely impermeable to solutes

Psi (osmotic coefficient)= zero if it completely aggregates into a single particle

Question 3

osmolality

Answer 3

C (osm) = psi * n * c(solute)

osmolal concentration= osmoles/ kg water

Question 4

tonicity of a physiological salt solution

Answer 4

refers to its effect on the volume of a cell placed in it

isotonic= maintains the cell volume

Hypotonic= cell expands (less osmolyte concentration extracellularly)- cell lysis

hypertonic = cell shrinks (more osmolyte concentration) ie crenation

Question 5

quantitative description of the passive sources of energy driving the transcellular flux of water

Answer 5

Jv= hydraulic conductivity,( concentration difference, plus hydrostatic pressure difference)

psi and n are equal in the body typically

net filtration pressure= capilarry hydrostatic pressure+ osmotic ISF pressure- Pif- osmotic pressure of capillary

Pif is zero