RBC Lecture

Question 1

What is a Permeable Membrane?

Answer 1

• Everything can cross
• At equilibrium:
  1. [solute] of A= [solute] of B
  2. Volume of A= Volume of B

Question 2

What is a Semi-Permeable Membrane?

Answer 2

• 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

Question 3

What is a Permselective Membrane?

Answer 3

• Solvent can cross

- Solutes have DIFFERENT permeabilities

Question 4

What is the osmotic pressure equation?

Answer 4

pi= pgh

• pi= osmotic pressure
• p= density of the solution
• g= gravitation constant
• h= height difference of fluid in the tubes

Question 5

What is a non-electrolyte?

Answer 5

Molecules that don’t dissociate into multiple parts when put into solution
- Sucrose, urea, proteins, etc

Question 6

What is the osmolarity for non-electrolytes?

Answer 6

Molarity=osmolarity

Question 7

What is an electrolyte?

Answer 7

Molecules that dissociate into multiple parts when put into solution

Question 8

What is the osmolarity for electrolytes?

Answer 8

Molarity x dissociation #= osmolarity

Question 9

What is the Permeability Coefficient?

Answer 9

P= how fast things can cross the membrane

Question 10

Osmolarity terms compare what?

Answer 10

solutions

Question 11

What is Isoosmotic?

Answer 11

• 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

Question 12

What is Hypoosmotic?

Answer 12

• 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

Question 13

What is Hyperosmotic?

Answer 13

• 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

Question 14

What does Isotonic mean?

Answer 14

no net H2O flow

Question 15

What is an Isotonic solution? (compared to inside of cell)

Answer 15

no volume change

Question 16

What does Hypotonic mean?

Answer 16

• if A is hypotonic to B then:

A -H2O-> B

Question 17

What is a Hypotonic solution? (compared to inside of cell)

Answer 17

• cell swells; volume increases

- if too much then lysis of cells

Question 18

What does Hypertonic mean?

Answer 18

• if A is hypertonic to B then:

B -H2O-> A

Question 19

What is a Hypertonic solution? (compared to the inside of cell)

Answer 19

cell shrinks; volume decreases

Question 20

What are the features of Red Blood Cells (RBCs)?

Answer 20

1) no nucleus
2) few internal structures
3) little lipid bilayer “bags” of hemoglobin (Hb)

Question 21

What are the features and assumptions of the membrane of RBCs?

Answer 21

• selective permeable membrane
• H2O and urea cross the membrane quickly
• Assume K+, Na+, sucrose, and Hb don’t cross

Question 22

What are the contents of plasma?

Answer 22

H2O and solutes

Question 23

What are the contents of the Buffy Coat?

Answer 23

White blood cells (WBCs) and platelets

Question 24

How is the Hematocrit (Hct) measured?

Answer 24

Hct= vol of RBCs / total volume

Question 25

What is a Wintrobe tube used for?

Answer 25

used to measure the Hct; the % of total volume taken up by RBCs
Ex: 0.37 or 37%

Question 26

What are the normal Hct values for men and women?

Answer 26

Women: 36%-46% (0.36-0.46)
Men: 41%-53% (0.41-0.53)

Question 27

Why do men have a higher Hct than women?

Answer 27

• males have a higher Hct bc male androgens trigger RBC production
• females lose RBC bc of menstruation

Question 28

What is the Hct level in anemia and was causes it?

Answer 28

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

Question 29

What is the level of Hct in polycythemia and what are the causes?

Answer 29

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)

Question 30

What is the equation of the total volume of RBCs?

Answer 30

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)

Question 31

What is the equation of the solute concentration inside of an RBC? What is the assumption of S?

Answer 31

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

Question 32

What is the Osmometer equation?

Answer 32

V/Vo= ((Co - (bCo/Vo)) (1/C) + (b/Vo)

- Describes the changes in RBC volume when RBCs are put into different tonicity solutions

Question 33

What is the b/Vo value?

Answer 33

• 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

Question 34

What is V/Vo?

Answer 34

V/Vo= H/Ho

• H= measured Hct
• Ho= Hct in an isotonic solution
• on the y axis; isotonic = 1

Question 35

What are the axis on the plot for V/Vo and 1/C?

Answer 35

y-axis: V/Vo

x-axis: 1/C (mOsm^-1)