Final answer:
High levels of lactic acid in someone with sickle-cell disease are due to impaired oxygen transport. The sickle-shaped red blood cells cannot effectively deliver oxygen, leading to anaerobic metabolism which produces lactic acid.
Step-by-step explanation:
Unusually high levels of lactic acid could be present in a person suffering from sickle-cell disease primarily because of impaired oxygen transport. Sickle-cell disease is a genetic disorder where red blood cells become sickle-shaped and lose their flexibility, making it difficult for them to pass through capillaries and thereby reducing oxygen perfusion to various tissues in the body. When tissues do not receive enough oxygen, the body relies on anaerobic glycolysis for energy, which produces lactic acid as a byproduct. This process leads to increased lactic acid levels in the absence of adequate oxygen delivery.
Sickle-cell disease is characterized by the presence of crescent-shaped, elongated, and stiffened red blood cells, which cannot effectively deliver oxygen. Consequently, the blood's ability to transport oxygen is compromised, leading to a condition where oxygen-carrying capacity is reduced. This causes a shift from aerobic to anaerobic metabolism, which increases lactic acid production due to the lack of oxygen for complete glucose breakdown.