Red blood cells (erythrocytes). Red cell metabolism
Survival of the red cell in the circulation depends
upon the continuous utilization of glucose for the production
of energy. Two chemical pathways are employed, and both
are essential forthe normal life of the red cell. An
extraordinary number of enzyme systems participate in
these reactions and direct the energy evolved into appropriate
uses. Red cells contain neither a nucleus nor RNA (ribonucleic
acid, necessary for protein synthesis), so that cell
division and production of new protein are impossible.
Energy is not necessary for oxygen and carbon dioxide
transport, which depends principally on the properties
of hemoglobin. Energy, however, is needed for another
operation. There is a tendency for the extracellular
cation, sodium, to leak into the red cell and for potassium
to leak out; energy is required to operate a pumping
mechanism in the red cell membrane to maintain the normal
gradients (differences in concentrations) of these ions.
Energy is also required to convert methemoglobin to
oxyhemoglobin and to prevent the oxidation of other
constituents of the red cell.
