CHAPTER 3
Cellular Aspects of Active Transport
ERNEST SCHOFFENIELS
Institut Leon Fredericq, University of Liege, Liege, Belgium
I. Introduction
137
II. The Permeability Characteristics of a Living Membrane .
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138
A. Origin of the Concentration Difference Existing between
Two Liquid Phases Separated by a Living Membrane .
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138
B. Origin of the Potential Difference Existing across Most
Living Membranes
154
III. Cellular Differentiation and Permeability Characteristics
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157
A. Amphibian Skin
157
B. Intestinal Epithelium of the Turtle
163
IV. Relations between Inorganic Ions, Sugars, Amino Acids, Fatty
Acids, and Bioelectric Potentials
164
V. Some Aspects of the Regulation of the Intracellular Pool of
Free Amino Acids
168
VI. Hormones and Permeability Characteristics of Cellular Membranes
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179
A. Neurohypophyseal Hormones
179
B. Other Hormones
182
VII. Alkaline Earths and Permeability Characteristics of Living Membranes .
183
A. Passive Permeability
184
B. Active Transport
187
C. Possible Mechanism of Action
188
VIII. Chemical Nature of the Structures Responsible for the
Permeability Characteristics of Living Membranes
190
IX. Conclusions
193
References
195
I. Introduction
The ultimate purpose of the studies on living membrane permeability
is not only to obtain information concerning the organization and the
chemistry of such membranes, but also to integrate the various functions
which can be ascribed to the membrane within the more general framework of cell metabolism. Despite the important progress made during
the last decade, we are far from having a coherent picture of what is
happening at the cell boundary. Most of the work done in the permea137