Adenosine triphosphate , hydrolysis active transport

Active Transport. Maintenance of the appropriate concentrations of K" and Na" in the intra- and extracellular fluids involves active transport, ie, a process requiring energy (53). Sodium ion in the extracellular fluid (0.136—0.145 AfNa" ) diffuses passively and continuously into the intracellular fluid (<0.01 M Na" ) and must be removed. This sodium ion is pumped from the intracellular to the extracellular fluid, while K" is pumped from the extracellular (ca 0.004 M K" ) to the intracellular fluid (ca 0.14 M K" ) (53—55). The energy for these processes is provided by hydrolysis of adenosine triphosphate (ATP) and requires the enzyme Na" -K" ATPase, a membrane-bound enzyme which is widely distributed in the body. In some cells, eg, brain and kidney, 60—70 wt % of the ATP is used to maintain the required Na" -K" distribution. 

The transport is directly coupled to adenosine triphosphate (ATP) hydrolysis, which is known as primary active transport. 

The Na, K -ATPase is known to actively pump Na out and into a cell against their concentration gradients. The active transport of these ions is tightly coupled to hydrolysis of adenosine 5 -triphosphate (5 -ATP). For every molecule of 5 -ATP... 

Direct coupling of adenosine triphosphate (ATP) hydrolysis is an example of an active transport process. The most important of these in the nephron is Nafi K -ATPase, which is located on the basolateral membranes of the tubulo-epithelial cells (Figure 45-6). This enzymatic transporter accounts for much of renal oxygen consumption and drives more than 99% of renal sodium reabsorption. Other examples of primary active transport mechanisms are a Ca " -ATPase, an H -ATPase, and an H, K -ATPase. These enzymes establish ionic gradients, polarizing cell membranes and thus driving secondary transport processes. 

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