Important aspects of the metabolism of the red blood cell
- The RBC is highly dependent upon glucose as its energy source, for which its membrane contains high affinity glucose transporters.
- Glycolysis, producing lactate, is the mode of ATP production
- Because RBCS lack mitochondria, there is no production of ATP by oxidative phosphorylation.
- The RBC has a varitey of transporters that maintain ionic and water balance
- Production of 2,3 bisphosphoglycerate by reactions closely associated with glycolysis is important in regulating the ability of Hb to transport oxygen.
- The pentose phosphate pathway of the RBC metabolizes about 5 to 10% of the total flux of glucose and produces NADPH
- Hemolytic anemia due to deficiency of activity of glucose 6 phosphate dehydrogenase is common
- The iron of Hb must be maintained in ferrous state. Ferric ion is reduced to ferrous form by action of NADH dependnent methemoglobin reducatse system involving cytochrome b5 reducatse and cytochrome b5.
*While biosynthesis of glycogen, fatty acids, protein, nucleic acids does not occur in RBC , some lipids eg cholesterol in the red cell membrane can exchange with corresponding plasma lipids. - The RBC contain certain enzymes of nucleotide metabolism eg adenosine deaminase, pyrimidine nucleotidase, and adenylyl kinase. Deficiencies of these enzymes are involved in some cases of hemolytic anemia.
*When RBCs reach the end of their lifespan, the globin is degraded to aminoacids , the iron is released from heme and reutilized and the tetrapyrrole component of heme is comverted to bilirubin, which is mainly excreted into the bowel via bile.