Question

Red blood cells in the lungs are sufficiently oxygenated to carry out aerobe glycolysis. Why do they, however, metabolize glycose to lactate?

Answer 1

answer: The conversion of glucose to lactate in the presence of oxygen has been termed aerobic glycolysis or aerobe glycolysis.

Erythrocyte :  red blood cell, which (in humans) is typically a biconcave disc without a nucleus. Erythrocytes contain the pigment haemoglobin, which imparts the red colour to blood, and transport oxygen and carbon dioxide to and from the tissues.

why do they ?

As erythrocytes lack mitochondria they are not able to use fats or generate energy from Krebs cycle. Though they have enzymes to synthesize glycogen the balance between synthesis and breakdown favours breakdown. Normal erythrocytes do not have glycogen and depend on a continuous supply of glucose to meet their energy requirements. Glucose enters the erythrocyte freely by facilitated diffusion. Insulin does not have any effect on the entry of glucose into the erythrocyte.

They erythrocyte( red blood cell) metabolism needs ATP as a source of energy and NADH and NADPH cofactors. The erythrocyte( red blood cell) does not synthesize nucleic acids but it has a small requirement for ribose to synthesize nucleosides for energy transfer The metabolic needs of erythrocytes ( red blood cell) are met by metabolism of glucose through three pathways glycolysis, the hexose monophosphate shunt and Rapport-Luebering glycolytic shunt.

how glycolysis work in red blood cell if there is no mitrocondria

Glycolysis is a process in which one molecule of glucose is converted to two molecules of pyruvate with the a net formation of two ATP and two NADH molecules. The energy released in the process stored as ATP. The electron released in the conversion of glyceraldehyde-3-phosophate to 1,3-bisphosphoglycerate is accepted by NAD⁺ Glycolysis can not proceed in the absence of an electron acceptor. NADH produced by glycolysis is transported to the mitochondria where it generates a net of 2 ATPs (3 ATP are generated but one is consumed to transport NADH into the mitochondria). Erythrocytes do not have mitochondria. Methaemoglobin reductase is the only sink for NADH. Glycolysis can proceed only if NAD⁺ is regenerated. Conversion of pyruvate to lactate by lactate dehydrogenase regenerates NAD⁺ allowing glycolysis. The end product of glycolysis in erythrocytes(red blood cells) is lactate.