Biology 304
Membrane Physiology

The cell membrane is highly selective, though it is only adapted to control molecules with which it has had evolutionary experience. In other words, some of the molecules we used in lab would never be found in the blood of a pig or trout (or sparrow, or turtle), so one would not expect specific transporters or channels for these molecules. Ergo, if these unknown molecules can’t squeeze into transporters for similar molecules (e.g. thiourea fitting into a urea transporter), the molecule either has to be able to dissolve through the lipids of the membrane or it just doesn’t get inside the cell.

Use the data from your lab manual, as well as your knowledge of chemistry (and the chemical structures on page 16), as well as the data below, to determine how the molecules are getting through the membrane (if in fact they are).

 

  Figure 1. Stock solution and haemolysis tracings as recorded by a spectrophotometer and recorded by the iWorx data acquisition system. New stock solution was added to thiourea at the arrow; the tube was then inverted and immediately put into the spectrophotometer.

 

Average haemolysis times for test solutions on both pig and fish blood from five of the last six years' Biology 304 classes. The actual numbers aren’t as important as the order in which haemolysis occurs, within each group of solutions.

FISH BLOOD

 

 

 

 

 

 

  Time to haemolysis (s)

 

Solution

2008

2007

2005

2004

2003

 

urea

49

83

99

78

114

thiourea

37

44

43

62

52

 

 

 

 

 

 

ethylene glycol

63

12

8

11

9

glycerol

97

123

130

105

120

erythritol

298

327

480

1893

 

 

 

 

 

 

 

glucose

1375

442

660

2010

 

sucrose

1398

254

372

2280

 

xylose

1334

540

540

1740

 

 

 

 

 

 

 

methanol

27

10

12

12

7

 

 

 

 

 

 

1-propanol

48

8

10

13

5

1-butanol

 n/a

8

8

14

8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PIG BLOOD

 

 

 

 

 

 Time to haemolysis (s) 

 

Solution

2008

2007

2005

2004

2003

 

urea

9

10

5

22

16

thiourea

72

50

59

66

41

 

 

 

 

 

 

ethylene glycol

20

11

12

34

27

glycerol

309

42

197

103

134

erythritol

 

 

 

1465

412

 

 

 

 

 

 

glucose

 

 

 

1520

 

sucrose

 

 

 

2265

906

xylose

 

 

 

1814

121

 

 

 

 

 

 

methanol

7

8

6

9

5

 

 

 

 

 

 

1-propanol

9

9

8

11

7

1-butanol

 

10

10

11

9

Reprints:

Hunter, F.R. 1976. Permeability of trout erythrocytes to nonelectrolytes. Biol Bull 151: 322-330.

Concha, I.I., F.V. Velasquez, J.M. Martınez, C. Angulo, A. Droppelmann, A.M. Reyes, J.C. Slebe, J.C. Vera, and D.W. Golde. 1997.  Human Erythrocytes Express GLUT5 and Transport Fructose. Blood. 89: 4190-4195.

Jacobs, M.H. 1931. Osmotic Hemolysis and Zoölogical Classification. Proceedings of the American Philosophical Society. 70: 363-370.

Naccache, P. and R. I. Sha'afi. 1973. Patterns of Nonelectrolyte Permeability in Human Red Blood Cell Membrane. J Gen. Physiol. 62: 714-736. This reference is particularly useful.

Walsh, P.J., C.M. Wood, S.F. Perry and S. Thomas. 1994. Urea Transport by Hepatocytes and Red Blood Cells of Selected Elasmobranch and Teleost Fishes. J. Exp. Biol. 193: 321–335.

R.F. Lauff
Department of Biology
St. Francis Xavier University
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