Problem Set 4

 

1)                  Draw the following structures:

cis-9-decenoic acid

 

18:1cD11

 

Saturated FA w/ Tm < 30oC

 

 

2)                  If Iextract the membrane lipids from 4.74*109 erythrocytes and spread them out on the surface of water in a tray, they form a monolayer of 0.89 m2.The surface area of an average erythrocyte is ~ 100 mm2.Show that the membrane is a bilayer.

 

 

3)                  How many moles of K+ will diffuse across the erythrocyte membrane in one minute under the following conditions?

[K+]in = 100 mM

[K+]out = 15 mM

Surface Area of erythrocyte: 100 mm2 = 100*10-12 m2

Permeability P of K+ = 2.4*10-10 cm-sec-1 (from Table 10.6)

 

4)                  If the erythrocyte volume is 100 mm3, what percent of the internal K+ will leak out in 1 minute?

 

 

5)                  A membrane-bound cell has [NaCl] = 0.1 M on the outside and 0.01 M on the inside at a temperature of 37oC.What is the membrane potential when the membrane is permeable to:

a.       Na+?

 

 

b.      Cl-?

 

 

c.       Both?

 

 

6)                  In the nerve cells from a Roswell alien, you find the following cellular and extracellular monovalent ion concentrations:

 

 

K+

Na+

Cl-

Inside

55 mM

312 mM

88 mM

Outside

310 mM

80 mM

250 mM

 

����������������������� Relative permeabilities:

 

Na+

1.0

K+

0.07

Cl-

0.25

 

����������������������� What�s the membrane potential at equilibrium?