Harvard-MIT Division of Health Sciences and Technology HST410J: Projects in Microscale Engineering for the Life Sciences, Spring 2007 Course Directors: Prof. Dennis Freeman, Prof. Martha Gray, and Prof. Alexander Aranyosi Lecture 4
February 15, 2007
HST.410J16.021J
Dissolution Transport
and diffusion through
through
water
lipid bilayer channels
Transport
Pumps
Figure from Weiss, T. F. Cellular Biophysics,
Vol. I. Cambridge, MA: MIT Press, 1996.
Courtesy of MIT Press. Used with permission.
Intracellular
Membrane
A
U
Extracellular
lipid
bilayer
I
I
""Ir
0
- 0
0.01
0
1
Figure from Weiss, T. F. Cellular Biophysics,
Vol. I. Cambridge, MA: MIT Press, 1996.
Courtesy of MIT Press. Used with permission.
2
3 4 5 6
Time (h)
7
8
~
0
:
, ,
,
1
3 4 5 6
Time (h)
2
, ,
, ,
7
8
Vial 1
Vial 2
Vial 3
Vial 4
Vial N
Cells loaded
with solute n
0.
tI,
..
•
--"
,-
Flow tube
Sampling chambers
u u u u u
Figures from Weiss, T. F. Cellular Biophysics,
Vol.I. Cambridge, MA: MIT Press, 1996.
Courtesy of MIT Press. Used with permission.
Solution free
of solute n
0.05
1
,
0
10
20
Time (ms) 30 integral
membrane solute
protein
\ f
lipid
bilayer
I
membrane
Figure from Weiss, T. F. Cellular Biophysics,
Vol.I. Cambridge, MA: MIT Press, 1996.
Courtesy of MIT Press. Used with permission.
0
0
30
60
90
Time (minutes)
Image removed due to copyright restrictions.
Illustration of a water channel in a cell membrane
120
Water transport in digestive system
Daily trafflc
.
.
.
800 g food + 1.2 L water ingested daily
1.5 L saliva
2 L gastric secretions
0.5 L bile
7 L digestive fluids
1.5 L pancreatic secretions
1.5 L intestinal secretions
ancrear
I
15 pounds ofwater (10% of body weight)
secreted and reabsorbed daily
Osmosis Observations
..
.
Henri Dutrochet (early 1800s)
first described phenomenon and called it osmosis
developed first osmometer: animal bladder filled
with test solution, plunge into water, swlls, turgid
pressure greater for solutions Vvlth more solute
water
..
..
Wllhelm Pfeffer (mid 1800s)
osmosis can be stopped with hydraulic pressure
thistle tube + animal bladder (or artificial membrane by late 1800s)
- water flows in direction to equalize sugar concentration
- hydraulic pressure develops
- flow stops vvtlen osmotic pressure = hydraulic pressure
pressure proportionalto concentration of solute
pressure increases slightly Vvlth temperature
Thistle
1
Water
1
Figure from Weiss, T. F. Cellular Biophysics,
F'o'ol. I. Cambridge, MA: MIT Press, 1996.
Courtesy of MIT Press. Used with permission.
..
..
Henricus van't Hoff (1886)
formulated mathematical law
count number of particles in volumeV
measure temperatureT
osmotic pressure = pressure produced by gas with same
number of particles, same volume, and same pressure
van't Hoff's Law
"/\-
pressure
molar gar
concentration
'
8.314 Jl(mo1.K)
.
salts are different
..
.
Svante Arrhenius (1884) PhD (age 25): dissolution of salts into ions NaCl + Na+ + C I (;. conducts electricity) count ions as separate particles + van' t Hoff s law works for salts as well
osmdic
pressure
[Pa=Nlm2]
-
Arbacia eggs
Figure from Weiss, T. F. Cellular Biophysics,
Vol.I. Cambridge, MA: MIT Press, 1996.
Courtesy of MIT Press. Used with permission.
I
I
I
I
Tune (minutes)
Tune (minutes)
Time (mrnutes)
Figure from Weiss, T. F. Cellular Biophysics, Vol.I. Cambridge, MA: MIT Press, 1996. Courtesy of MIT Press. Used with permission.