Chapter 53: Red Blood Cells: Structure & Function

Red Blood Cells: Structure & Function details the specialized structure of mature erythrocytes, which lack organelles such as mitochondria and nuclei to maximize hemoglobin content, relying on a flexible cytoskeleton composed of spectrin, actin, and ankyrin to maintain their biconcave shape and navigate capillary beds. The text explains the unique metabolic requirements of red blood cells, which depend exclusively on anaerobic glycolysis for ATP production via the glucose transporter GLUT1, and utilizes the 2,3-bisphosphoglycerate shunt to stabilize the T-state of hemoglobin for optimal oxygen delivery. Significant attention is given to the management of oxidative stress through the pentose phosphate pathway and glutathione production, highlighting how glucose-6-phosphate dehydrogenase (G6PD) deficiency leads to hemolytic anemia due to the inability to neutralize reactive oxygen species. The summary covers the critical role of the NADH-cytochrome b5 reductase system in preventing methemoglobinemia by reducing ferric iron back to the ferrous state required for oxygen binding. Furthermore, the chapter elucidates the molecular basis of the ABO blood group system, defined by specific glycosyltransferases that attach distinct sugar residues to H substance glycosphingolipids. Membrane dynamics are also explored, including the function of Band 3 (anion exchange protein) in chloride-bicarbonate transport and the pathologies associated with cytoskeletal defects, such as hereditary spherocytosis and elliptocytosis. Finally, the biochemistry of platelets is examined, including their formation from megakaryocytes, the contents of their dense and alpha granules, and the genetic basis of bleeding disorders like von Willebrand disease and Glanzmann thrombasthenia.