ACTIVE TRANSPORT ;;
It is a process in which specific carriers move the molecules and ions against concentration electrical or pressure gradient like facilitated diffusion it is saturable however it differs from facilitated diffusion in that net movement always occurs against a gradient and requires energy which is supplied by atp (adenosine tri phosphate)
sodium potassium atp ase (na+k+atpase)enzyme is the specific active transport carrier for na+and k+across excitable cell membranes of nerves and muscles this transport system is known as na+k+atp ase pump energy supplied by the breakdown of atp allows the carrier to pick up Na+ ions from inside of the cell and drops them off outside after this the carrier changes the shape pick up K+ions and drop them off inside additional energy is required to repeat the process the carrier may move empty handed or change the shape in either direction this process keeps the excitable membranes polarized positively charged outside due to high concentration of Na+ and negatively charged inside due to high concentration of Cl- that is associated with k+
in addition to Na+ k+ ATPase pump there is Na+ ATPase pump transporting Na+Ca++ATPase pump transporting Na+Ca++and H+K+ATPase pump responsible for acid secretion in stomach in non excitable cells these pumps (Na+K+ATPase Ca++ATPase )help in maintaining the normal ionic composition that is essential for the regulation of intracellular activities the active transport of Na+is also important for the regulation of cellular volume
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