. Biological transport. Biological transport; Biological Transport. BIOLOGICAL TRANSPORT Migration by more than one process As the level of a solute is increased, one frequently finds that the rate does not entirely stop increasing; instead it still continues to increase gradually in a linear fashion, as illustrated in Figure 19. This result shows that at least two processes participate, one satu- rable and one that fails to saturate within the range of study. (The latter probably includes not only diffusion but also, or instead, a hard-to-saturate passive mediation, like the process seen abov
. Biological transport. Biological transport; Biological Transport. BIOLOGICAL TRANSPORT Migration by more than one process As the level of a solute is increased, one frequently finds that the rate does not entirely stop increasing; instead it still continues to increase gradually in a linear fashion, as illustrated in Figure 19. This result shows that at least two processes participate, one satu- rable and one that fails to saturate within the range of study. (The latter probably includes not only diffusion but also, or instead, a hard-to-saturate passive mediation, like the process seen above to participate in the escape of amino acids from cells.) A situation of this kind has been studied for the isolated diaphragm in its uptake of radioactive a-aminoisobutyric acid in the presence or absence of added insulin (see Figure 19) (Akedo and Christensen, 1962b). In his analysis, Akedo separated these two components by in- tegrating the equation giving the total flux as the sum of two fluxes:. I I l I l I L 4 8 12 16 20 [a-Aminoisobutyrate] raM Figure 19 Uptake by two distinct mechanisms. a-Aminoisobutyr- ate entry into the isolated rat diaphragm in vitro. The upper curve shows the total rate of uptake (corrected for entry into the inulin space) as a function of the extracellular concentration. The middle curve shows the calculated rate of the saturable process; the lower curve, of the process not subject to saturation up to M. [Results of Akedo, H., and Christensen, H. N. (1962), /. Biol. Chevu, 237, 1180.] 5°. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Christensen, Halvor N. New York, W. A. Benjamin
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