Biological Sciences 300/301, Smith College | Neurophysiology Case 2: Why do red blood cells need pumps?
	PART A
	Mature red cells lack mitochondria and RNA, and the Krebs cycle is inactive. These cells are incapable of hemoglobin synthesis. Energy is derived from glucose via the Emden-Meyerhof pathway and the hexose monophosphate shunt. Survival of red cells within the circulation depends upon the persistence of energy producing metabolic processes. These are necessary to maintain cationic gradients across the red cell membrane. By means of an active transport mechanism that depends on interaction between the membrane and ATP, sodium is pumped out of the cell and potassium moves inward. When ATP is reduced, erythrocytes tend to become more spherical because of inward movement of sodium and water. Mountcastle, Medical Physiology, 12th ed.
	Table 12.1. Extracellular and Intracellular Ion Concentrations Concentration (mM) Ion Intracellular Extracellular Mammalian cell (eg, erythrocyte) K+ 140 5 Na+ 5-15 145 Cl- 4 110 Ca2+ 0.0001 2.5-5   Squid axon K+ 400 20 Na+ 50 440 Cl- 40-150 560 Ca2+ 0.0001 10 Cooper: The Cell, a molecular approach, 2nd ed