Final answer:
Lactic acid is involved in exercise and anaerobic glycolysis, with levels used to identify medical conditions like meningitis or to understand muscular fatigue during intense activity, through lactate dehydrogenase (LDH) enzyme activities.
Step-by-step explanation:
Lactic acid (CH3CH(OH)CO₂H) is a by-product of anaerobic glycolysis and is involved in various physiological processes, including exercise and fermentation. Elevated lactic acid levels in the blood and muscle may contribute to fatigue during intense physical activity, though this is a more complex issue involving factors such as energy availability and perception of pain. Additionally, the concentration of lactic acid is increased in certain medical conditions, such as severe brain ischemia where it is produced due to anaerobic glycolysis. The normal lactic acid content of cerebrospinal fluid (CSF) ranges from 1.8 to 2.4 mg/dl, and measurements of lactic acid in CSF are utilized to differentiate between bacterial and viral meningitis. When levels are higher than the normal range, it can be an indicator of bacterial infection or other conditions leading to increased anaerobic glycolysis within the brain. Lactate dehydrogenase (LDH) is the enzyme that catalyzes the conversion of pyruvic acid to lactic acid and vice versa, playing a pivotal role in the metabolic processes during both exercise and rest states.