. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PHOSPHATE TRANSPORT BY H. DIMINUTA 341 0 25 - 0 20 - 0 15 -. 0 10 - 0 05 - FIGURE 2. Absorption of radiophosphate by Hymenolepis diminula as a function of phosphate con- centration ( mA/). Each point is an average value from two experiments. S = phosphate concentra- tion in mA/, V = /^mol/g ethanol-extracted dry wt/2 min. • = Total uptake; O = mediated component; • = diffusive component. Effect of substrate concentration The absorption process was a straight line relationship over a substrate concentra- tion range of 0
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PHOSPHATE TRANSPORT BY H. DIMINUTA 341 0 25 - 0 20 - 0 15 -. 0 10 - 0 05 - FIGURE 2. Absorption of radiophosphate by Hymenolepis diminula as a function of phosphate con- centration ( mA/). Each point is an average value from two experiments. S = phosphate concentra- tion in mA/, V = /^mol/g ethanol-extracted dry wt/2 min. • = Total uptake; O = mediated component; • = diffusive component. Effect of substrate concentration The absorption process was a straight line relationship over a substrate concentra- tion range of mA/ to 20 mA/ suggesting diffusion might be involved. At lower substrate concentrations ( mA/") uptake was nonlinear and appeared to be a combination of mediated uptake and diffusion (Fig. 2). Subtracting the diffusive com- ponent obtained by deleting sodium from the incubation medium from the overall rate, the mediated process was unveiled with calculated Vmax and Km values of jumol ethanol-extractable radioactive inorganic phosphate/g ethanol-extracted dry wt/2 min and mA/, respectively (Figs. 3, 4), obtained from the Lineweaver-Burk plot. Using Hanes-Woolf plot, the corresponding values of yumol ethanol-ex- tractable radioactive inorganic phosphate/g ethanol-extracted dry wt/2 min and mA/ were obtained. From studies with 3H-PEG, it was found that after rinsing and blotting dry three times, only to /j,\ of the incubation medium was carried over as unstirred layer per sample of worm ( g ethanol-extracted dry weight). Since this was only a minute volume and it did not significantly affect the calculated results, the unstirred layer was not labelled in the subsequent incubation studies. With increasing concentrations of stable phosphate in the incubation medium, the initial rate of uptake of mA/labelled phosphate decreased and then levelled off (Fig. 5). This result supported the hypothesis that mediated transport was
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
