Epithelial cells energy

Active reabsorption occurs when the movement of a given substance across the luminal surface or the basolateral surface of the tubular epithelial cell requires energy. Substances that are actively reabsorbed from the tubule include glucose amino acids and Na+, POy3, and Ca++ ions. Three generalizations can be made regarding the tubular reabsorption of sodium, chloride, and water ... 

Reabsorption of Na+ ions is an active process 80% of the total energy expended by the kidneys is used for sodium transport out of the tubular epithelial cell. 

Figure 5. Doses averaged over all epithelial cells in the bronchial and alveolar regions of the lung per unit exposure to potential alpha-energy as a function of aerosol size, compared with doses to basal cells for several models of airway size and clearance behaviour.

Figure 6. Doses averaged over epithelial cells in segmental bronchi per unit exposure to potential alpha-energy.

Ferin, J. (1977). Effect of particle content of lung on clearance pathways. In Pulmonary Macrophage and Epithelial Cells (Sanders, C.L., Schneider, R.P., Dagle, G.E. and Ragan, H.A., Eds.). Technical Information Center, Energy Research and Development Administration, Springfield, VA, pp. 414-423. 

Since the intracellular concentration of most amino acids is considerably greater than that in the plasma (Table 8.2), the transport of these amino acids is an energy-requiring process. This is achieved via the Na+ gradient across the plasma membrane, which is maintained by the ATP-dependent Na pump the NaVK+ ATPase (Figure 8.5). This is similar to that of the transport of glucose across the luminal membranes of epithelial cells in the gut and in the tubules is the kidney cortex. 

The fatty acids of triacylglycerols furnish a large fraction of the oxidative energy in animals. Dietary triacylglycerols are emulsified in the small intestine by bile salts, hydrolyzed by intestinal lipases, absorbed by intestinal epithelial cells, reconverted into triacylglycerols, then formed into chylomicrons by combination with specific apolipoproteins. 

Figure 11. Selected ion monitoring from mass spectrometry of glycolipids of epithelial cells of the two rat strains. A total of 200 fig each of the permethylated-reduced mixture was evaporated by a temperature rise of 5°C/min, and mass spectra were recorded each 38 sec. Electron energy was 34 eV, acceleration voltage 4 kV, trap current 500 fiA, and ion source temperature 290°C.

A typical cross section of a cilium shows a ring formed by nine pairs of microtubules and two central tubules, i.e., the so-called nine + two pattern. Each doublet contains an A and a B subfibril with an inner and an outer dynein arm (a complex protein with ATPase activity) located on the A subfibril with radial spokes extending toward the central doublet. The ciliary membrane, which is an extension from the cell membrane of the epithelial cell, encloses the microtubules. The motion of the cilia is dependent on the sliding of the outer doublets past one another with the energy provided by adenosine triphosphate (ATP) through dynein ATPase activity. 

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