Glucose extracellular transfer

Figure 19. P-NMR spectra of aerobic glucose-grown Escherichia coli. The arrows indicate the frequencies of the low-power pulses used in B to saturate the nucleotide triphosphate (NTP) peak. The peaks labelled P-" and Pf correspond to intracellular and extracellular Pj, respectively. Peak NTP, consists of approximately 50% ATP and 50% nonadenine nucleotide triphosphates. The difference spectrum A — B) shows transfer of saturation from NTP, to P, (from [36]).

Besides being used as adsorbent for gas molecules, both SWCNTs and MWC-NTs can be cast as a random network or a porous thin film on metal electrodes [57-59] or used as a three-dimensional scaffold [41,42] for biosensors. CNTs serve both as large immobilization matrices and as mediators to improve the electron transfer between the active enzyme site and the electrochemical transducer. Various enzymes, such as glucose oxidase and flavin adenine dinucleotide (FAD) can adsorb onto the CNT surface spontaneously and maintain their substrate-specific enzyme activity over prolonged times [57]. Recently, cells have been grown on CNT scaffolds which provide a three-dimensional permeable environment, simulating the natural extracellular matrix in a tissue [60-62]. 

Dehydroascorbic acid, the two-electron oxidised form of the vitamin, was taken up by human monocytic U-937 cells on the glucose transporter and reduced to ascorbate to a much greater extent than ascorbate itself was accumulated in the cells (May et al. 1999). In contrast to dehydroascorbic acid, ascorbate entered the cells on a sodium- and energy-dependent transporter. Intracellular ascorbate enhanced the transfer of electrons across the cell membrane to extracellular ferricyanide. Rates of ascorbate-dependent ferricyanide reduction was... 

Phosphorus is more readily absorbed from the intestinal tract than calcium. Approximately two-thirds of the phosphorus excreted is found in the feces, one-third in the urine. Between 10 and 20 % of phosphorus is found in tissues other than bone, and this phosphorus appears to have metabolic priority. The mechanisms which regulate deposition and release of phosphorus from bone are the same as those for calcium. Phosphorus in soft tissues plays a very vital role in many metabolic processes. The importance of adenosine triphosphate (ATP) in energy transfer systems has been discussed previously (p. 203, Chapter 16). Phosphorylation appears to be essential for the absorption of a number of nutrients, e.g., fatty acids and glucose. The phosphate radical is bound to proteins, fatty acids, carbohydrates, and enzymes. Phosphate is the chief inorganic anion of intracellular fluid, and phosphates of extracellular fluid participate in acid-base regulation. The inorganic phosphate level of blood ranges from 2 to 4 mg. per 100 ml. in adults and 3 to 5 mg. per 100 ml. in children. 

In MFC, the electrons are transferred via microbes constituting an electron transport system. The electron transport system may consist of a series of components in the bacterial extracellular matrix. Figure 1.18 gives the detailed description of the microbes and their respective mediators used for glucose substrates. 

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