- One very common pump and found in
all the cells of the body is the sodium-potassium
pump. This pump is made up of three protein
molecules that span the cell membrane.
- It has three intracellular sites
that have a high affinity to sodium and two
extracellular sites that have a high affinity to
- It has also got ATPase activity
i.e. it can act as an enzyme to hydrolyse one
phosphate bond from an ATP molecule.
- When both the sodium and potassium
sites are full, the ATPase is activiated and
splits an ATP molecule into ADP, Phosphate group
- The energy is utilised to bring
about a conformational change in the proteins
whereas the sodium sites project into the
extracellular space and the potassium sites are
presented into the intracellular space. At the
same time the energy releases these ions.
- Thus this pump, removes three
sodium ions from the intracellular space and
exchanges them to two potassium ions.