RBC Lecture Flashcards
What is a Permeable Membrane?
- Everything can cross
- At equilibrium:
1. [solute] of A= [solute] of B
2. Volume of A= Volume of B
What is a Semi-Permeable Membrane?
- Only the solvent (H2O) can cross
- At equilibrium: osmotic pressure generated by the solute in A EQUALS the hydrostatic pressure generated by the extra solvent in A from B
What is a Permselective Membrane?
- Solvent can cross
- Solutes have DIFFERENT permeabilities
What is the osmotic pressure equation?
pi= pgh
- pi= osmotic pressure
- p= density of the solution
- g= gravitation constant
- h= height difference of fluid in the tubes
What is a non-electrolyte?
Molecules that don’t dissociate into multiple parts when put into solution
- Sucrose, urea, proteins, etc
What is the osmolarity for non-electrolytes?
Molarity=osmolarity
What is an electrolyte?
Molecules that dissociate into multiple parts when put into solution
What is the osmolarity for electrolytes?
Molarity x dissociation #= osmolarity
What is the Permeability Coefficient?
P= how fast things can cross the membrane
Osmolarity terms compare what?
solutions
What is Isoosmotic?
- generate the same pi; two solutions with the same osmolarity and generating equal osmotic pressure (pi)
ex:
A= 2mM sucrose= 2mOsm
B= 1mM NaCl= 2 mOsm
What is Hypoosmotic?
- generates a lower pi
- a solution having a lower osmolarity and osmotic pressure (pi) than another solution
ex:
A= 1mM sucrose= 1 mOsm is hypoosomotic to
B= 1mM NaCl= 2mOsm
What is Hyperosmotic?
- generates higher pi
- a solution having a greater osmolarity and osmotic pressure(pi) than another solution
Ex:
A= 2mM sucrose is hyperosmotic to
B= 0.5 mM NaCl
What does Isotonic mean?
no net H2O flow
What is an Isotonic solution? (compared to inside of cell)
no volume change
What does Hypotonic mean?
- if A is hypotonic to B then:
A -H2O-> B
What is a Hypotonic solution? (compared to inside of cell)
- cell swells; volume increases
- if too much then lysis of cells
What does Hypertonic mean?
- if A is hypertonic to B then:
B -H2O-> A
What is a Hypertonic solution? (compared to the inside of cell)
cell shrinks; volume decreases
What are the features of Red Blood Cells (RBCs)?
1) no nucleus
2) few internal structures
3) little lipid bilayer “bags” of hemoglobin (Hb)
What are the features and assumptions of the membrane of RBCs?
- selective permeable membrane
- H2O and urea cross the membrane quickly
- Assume K+, Na+, sucrose, and Hb don’t cross
What are the contents of plasma?
H2O and solutes
What are the contents of the Buffy Coat?
White blood cells (WBCs) and platelets
How is the Hematocrit (Hct) measured?
Hct= vol of RBCs / total volume
What is a Wintrobe tube used for?
used to measure the Hct; the % of total volume taken up by RBCs
Ex: 0.37 or 37%
What are the normal Hct values for men and women?
Women: 36%-46% (0.36-0.46)
Men: 41%-53% (0.41-0.53)
Why do men have a higher Hct than women?
- males have a higher Hct bc male androgens trigger RBC production
- females lose RBC bc of menstruation
What is the Hct level in anemia and was causes it?
Low Hct
- bleeding (lose RBC)
- low iron (need iron to make Hb and for maturation of RBCs)
- pregnancy (expansion of plasma vol)
- RBC breakage (hemolytic anemias, immune attack on RBCs)
- some types of kidney disease (decreased erythropoietin (EPO) production)
*EPO= hormones that makes RBCs
What is the level of Hct in polycythemia and what are the causes?
High Hct
- dehydration (decreased plasma vol)
- hereditary overproduction of RBCs (polycythemia vera)
- low blood oxygen (live at high altitude, heart/lung disease, smokers)
- blood packing (transfuse extra RBCs)
- EPO injections (make extra RBCs)
What is the equation of the total volume of RBCs?
V= W+b
- V= total volume of an RBC
- W= volume of H2O in an RBC (can cross)
- b=”osmotically inactive volume” (can’t cross- Hb, other solutes)
What is the equation of the solute concentration inside of an RBC? What is the assumption of S?
C= S/W
- C= [solute] inside of an RBC
- S= # of particles
- W= volume of H2O in an RBC
- Assume that solutes don’t cross the RBC membrane therefore S is constant
What is the Osmometer equation?
V/Vo= ((Co - (bCo/Vo)) (1/C) + (b/Vo)
- Describes the changes in RBC volume when RBCs are put into different tonicity solutions
What is the b/Vo value?
- where the line crosses the y-axis
- in humans: 0.4-0.45
- Hypertonic solutions plot closer to the origin, lower values
- Hypotonic solutions plot further from the origin, higher values
What is V/Vo?
V/Vo= H/Ho
- H= measured Hct
- Ho= Hct in an isotonic solution
- on the y axis; isotonic = 1
What are the axis on the plot for V/Vo and 1/C?
y-axis: V/Vo
x-axis: 1/C (mOsm^-1)
