Lactic Acid Lowers Blood pH in Anaerobic Conditions

Steps:

• Anaerobic respiration in muscle cells occurs when oxygen is limited, producing ATP via glycolysis.
• Glycolysis ends with pyruvate converting to lactic acid (lactate + H+).
• Lactic acid diffuses from muscle cells into the bloodstream.
• In blood, lactic acid dissociates, releasing H+ ions that increase acidity and reduce pH.

Why C is correct:

• Lactic acid is a weak acid (CH3CH(OH)COOH ⇌ CH3CH(OH)COO- + H+) that ionizes in blood, elevating H+ concentration and lowering pH per the pH definition (-log[H+]).

Why the others are wrong:

• A: CO2 production occurs in aerobic respiration, not anaerobic, and its blood dissolution forms carbonic acid but isn't the primary anaerobic effect.
• B: Muscle cells produce lactic acid, not ethanol, which is a yeast fermentation product and doesn't affect pH similarly.
• D: Oxygen removal reduces hemoglobin saturation but doesn't produce acidic byproducts to alter pH.

Final answer: C