Transport of sucrose

As before, by dividing Pe by PABL, the transport kinetics is seen to be 32% ABL-controlled, or, upon dividing Pe by Pm the overall transport of sucrose is seen to be 51% collagen matrix-controlled by molecular size restricted diffusion. 

The inulin-containing vacuoles also often contain vesicles (Kaeser, 1983), more so in cells adjacent to the interfascicular cambium, and decreasing in number with increasing distance from the cambium. The largest are localized within the vacuole and contain fibrous or granular material. It is thought that the vesicles form in the cytoplasm and function in the transport of sucrose into the vacuole (for additional details, see Section 10.8). 

Inulin synthesis in the tubers occurs in the vacuoles of storage parenchyma cells. Kaeser (1983) proposed a model for the transport of sucrose into the central vacuole that involves the formation of vesicles within the cytoplasm that contain sucrose and inulin synthesis enzymes. The vesicles transfer their contents into the vacuole via two possible mechanisms (1) the cytoplasmic vesicle fuses with the tonoplast and through pinocytosis releases its contents into the vacuole, or (2) vesicles originating from plasmalemma invaginations are tied off into the vacuole, resulting in... 

Transport of sucrose from leaf cells into sieve... 

This discussion has indicated that the companion cells of the phloem may be involved in supplying energy to the sieve tubes both for the initial transport of sucrose into and out of sieve tubes and for its transport within the tubes. They may also be involved in the polarised... 

Wyse, R.E., Zamski, E. Tomos, A.D. (1986). Turgor regulation of sucrose transport in sugar beet tap root tissue. Plant Physiology, 81, 478-81. 

Figure 1. The correlation of transepithelial electrical resistance (TEER) with the transepithelial transport of 14C-sucrose in MDCK cell monolayers grown on microporous filters.

Figure 4. Transcellular transport of l4C-sucrose in filter-grown MDCK cell monolayers. Confluent MDCK monolayers in Transwells were treated at the basal compartment (closed squares) and the apical compartment (open squares) with 14C-sucrose (1 pCi/mL).

Ussing, H. H., Anomalous transport of electrolytes and sucrose through the isolated frog skin induced by hypertonicity of the outside bathing solution, Ann. N. Y. Acad. Sci. 1966, 137, 543-555. 

De Luca [3.5] recommends furthermore the addition of e. g. tertiary butylalcohol (TBA), to increase the transport of water vapor out of the product and to avoid collapse in sucrose-,... 

Sugar The hydrolysis of sucrose in the intestine produces both glucose and fructose, which are transported across the epithelial cells by specific carrier proteins. The fructose is taken up solely by the liver. Fructose is metabolised in the liver to the triose phosphates, dihydroxy-acetone and glycer-aldehyde phosphates. These can be converted either to glucose or to acetyl-CoA for lipid synthesis. In addition, they can be converted to glycerol 3-phosphate which is required for, and stimulates, esterification of fatty acids. The resulting triacylglycerol is incorporated into the VLDL which is then secreted. In this way, fructose increases the blood level of VLDL (Chapter 11). 

Complexes of alkali metals and alkaline-earth metals with carbohydrates have been reviewed in this Series,134 and the interaction of alkaline-earth metals with maltose has been described.135 Standard procedures for the preparation of adducts of D-glucose and maltose with the hydroxides of barium, calcium, and strontium have been established. The medium most suitable for the preparation of the adduct was found to be 80% methanol. It is of interest that the composition of the adducts, from D-glucose, maltose, sucrose, and a,a-trehalose was the same, namely, 1 1, in all cases. The value of such complex-forming reactions in the recovery of metals from industrial wastes has been recognized. Metal hydroxide-sugar complexes may also play an important biological role in the transport of metal hydroxides across cell membranes. 

FIGURE 20-35 Conversion of stored fatty acids to sucrose in germinating seeds. This pathway begins in glyoxysomes. Succinate is produced and exported to mitochondria, where it is converted to oxaloacetate by enzymes of the citric acid cycle. Oxaloacetate enters the cytosol and serves as the starting material for gluconeogenesis and for the synthesis of sucrose, the transport form of carbon in plants. 

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