3. CELLULAR ASPECTS OF ACTIVE TRANSPORT
195
In most of the studies dealing with the transfer of ions or molecules
we do not encounter too much difficulty in demonstrating the metabolic
dependence of a transport. We find, however, a challenging problem
when we try to give a physical meaning to the various constants appearing in our flux equations. A simple model, the pore membrane, has been
proposed on the basis of these equations. However, it is still a fact that
this model is far from being completely satisfactory. Such a mechanistic
model might be inadequate to explain the apparently simple behavior
of water, urea, thiourea, and so on.
Finally, it may be proposed that the comparative study of membrane
permeability illustrates two useful concepts in comparative biochemistry.
It has been pointed out that in the field of membrane permeability, the
differentiation seems to be achieved mainly through a spatial arrangement of permeability characteristics at the cell surface. This therefore
constitutes a good example of physiological radiation.
On the other hand, in the light of available data, we may speculate
on the chemical nature of the molecular architecture responsible for the
various permeability characteristics. It may tentatively be proposed that
the biochemical systems involved are closely related chemically. The
permeability characteristics of living membranes could then be considered as heterotypic expressions of a common biochemical system.
References
1. V. Koefoed-Johnsen and Η. H. Ussing, Acta Physiol Scand. 28, 60-76 (1953).
2. Η. H. Ussing and K. Zerahn, Acta Physiol Scand. 23, 110-127 (1951).
3. E. Schoffeniels, Arch, intern, physiol et biochem. 63, 361-365 (1955).
4. D. D. Van Slyke and G. M. Meyer, /. Biol Chem. 16, 197-233 (1913).
5. D. L. Oxender and Η. N. Christensen, /. Biol. Chem. 234, 2321-2324 (1959).
6. E. F. Gale, Advances in Protein Chem. 8, 285-391 (1953).
7. Η. N. Christensen, Τ. R. Riggs, and Ν. E. Ray, /. Biol. Chem. 194, 41-51
(1952).
8. E. Negelein, Biochem. Z. 323, 214-234 (1952).
9. R. M. Johnstone, Can. J. Biochem. and Physiol. 37, 589 (1959).
10. Η. N. Christensen, Μ. Κ. Cushing, and J. A. Streicher, Arch. Biochem. 23,
106-110 (1949).
11. Η. N. Christensen, Τ. R. Riggs, H. Fischer, and I. M. Palatine, J. Biol. Chem.
198, 15-22 (1952).
12. T. R. Riggs, B. A. Coyne, and Η. N. Christensen, /. Biol. Chem. 209, 395-411
(1954).
13. Η. N. Christensen and T. R. Riggs, /. Biol. Chem. 220, 265-278 (1956).
14. G. Wiseman, /. Physiol. (London) 120, 63-72 (1953).
15. H. Akedo, T. Sugawa, S. Yoshikawa, and M. Suda, /. Biochem. (Tokyo) 47,
124-130 (1960).
16. M. Baillien and E. Schoffeniels, Biochim. et Biophys. Acta 53, 521-536 (1961).
17. Η. N. Christensen and T. R. Riggs, /. Biol. Chem. 194, 57-68 (1952).
18. L. M. Birt and F. J. R. Hird, Biochem. J. 70, 277-286 (1958).
195
In most of the studies dealing with the transfer of ions or molecules
we do not encounter too much difficulty in demonstrating the metabolic
dependence of a transport. We find, however, a challenging problem
when we try to give a physical meaning to the various constants appearing in our flux equations. A simple model, the pore membrane, has been
proposed on the basis of these equations. However, it is still a fact that
this model is far from being completely satisfactory. Such a mechanistic
model might be inadequate to explain the apparently simple behavior
of water, urea, thiourea, and so on.
Finally, it may be proposed that the comparative study of membrane
permeability illustrates two useful concepts in comparative biochemistry.
It has been pointed out that in the field of membrane permeability, the
differentiation seems to be achieved mainly through a spatial arrangement of permeability characteristics at the cell surface. This therefore
constitutes a good example of physiological radiation.
On the other hand, in the light of available data, we may speculate
on the chemical nature of the molecular architecture responsible for the
various permeability characteristics. It may tentatively be proposed that
the biochemical systems involved are closely related chemically. The
permeability characteristics of living membranes could then be considered as heterotypic expressions of a common biochemical system.
References
1. V. Koefoed-Johnsen and Η. H. Ussing, Acta Physiol Scand. 28, 60-76 (1953).
2. Η. H. Ussing and K. Zerahn, Acta Physiol Scand. 23, 110-127 (1951).
3. E. Schoffeniels, Arch, intern, physiol et biochem. 63, 361-365 (1955).
4. D. D. Van Slyke and G. M. Meyer, /. Biol Chem. 16, 197-233 (1913).
5. D. L. Oxender and Η. N. Christensen, /. Biol. Chem. 234, 2321-2324 (1959).
6. E. F. Gale, Advances in Protein Chem. 8, 285-391 (1953).
7. Η. N. Christensen, Τ. R. Riggs, and Ν. E. Ray, /. Biol. Chem. 194, 41-51
(1952).
8. E. Negelein, Biochem. Z. 323, 214-234 (1952).
9. R. M. Johnstone, Can. J. Biochem. and Physiol. 37, 589 (1959).
10. Η. N. Christensen, Μ. Κ. Cushing, and J. A. Streicher, Arch. Biochem. 23,
106-110 (1949).
11. Η. N. Christensen, Τ. R. Riggs, H. Fischer, and I. M. Palatine, J. Biol. Chem.
198, 15-22 (1952).
12. T. R. Riggs, B. A. Coyne, and Η. N. Christensen, /. Biol. Chem. 209, 395-411
(1954).
13. Η. N. Christensen and T. R. Riggs, /. Biol. Chem. 220, 265-278 (1956).
14. G. Wiseman, /. Physiol. (London) 120, 63-72 (1953).
15. H. Akedo, T. Sugawa, S. Yoshikawa, and M. Suda, /. Biochem. (Tokyo) 47,
124-130 (1960).
16. M. Baillien and E. Schoffeniels, Biochim. et Biophys. Acta 53, 521-536 (1961).
17. Η. N. Christensen and T. R. Riggs, /. Biol. Chem. 194, 57-68 (1952).
18. L. M. Birt and F. J. R. Hird, Biochem. J. 70, 277-286 (1958).