PH1 01: Cell Membranes and Transmembrane Transport
Last Modified: 2016-03-08
What is the ratio of ECF to ICF?
What is the ratio of interstitial fluid (ISF) to plasma?
ECF : ICF
1 : 2
ISF : plasma
3 : 1
How is it measured?
millimeters height of Hg in a 1 cm2 area (mmHg)
How is it measured?
mol/L = osmol = Osm
osmol = molarity in mol/L x dissociation constant of substance
substances that do not dissociate, dissociation constant = 1
How would two solutions with equal osmolarity be termed in relation to one another?
solution of higher osmolarity is hyperosmotic to lower solution
in hypotonic solution, water enters it
hypertonic = more solutes than cell
in hypertonic solution, water leaves it
What two factors predict tonicity?
predicted by osmolarity and permeability of a membrane to solutes
they remain behind barrier to 'pull' water across membrane
tonicity is not a question of osmolarity
but also membrane permeability to particular solutes
osmolarity = number of particles in a solution
equivalence = valence of ions
2 mol/L (osmol)
2 charge equivalents
CaCl2 --> Ca2+ + 2Cl-
3 mol/L (osmol)
4 charge equivalents
RBCs burst in urea solution, but not sucrose
Which is the effective osmole?
urea enters cell, drawing water in
sucrose cannot cross membrane
sucrose is effective osmole
RBCs shrink in hypertonic solution
(more solutes outside, water leaves RBC)
non-polar = hydrophobic = no water can pass
more cholesterol makes membrane less permeable to water
= concentration gradient of A x membrane permeability to A x surface area of membrane
diffusion rate increased by
higher concentration gradient
higher membrane permeability
higher membrane surface area
A = R-GlcNAc -- Gal -- Fuc -- GalNAc
B = R-GlcNAc -- Gal -- Fuc -- Gal
AB = both A and B
List the types of transporters
one molecule at a time
two or more molecules at a time
two or more molecules in one direction
two or more molecules in opposite directions
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