During the course of normal cellular metabolism, the body generates large quantities of acid. Despite this, normal blood pH is maintained at a slightly alkaline pH of 7.4. Removal of which of the following is most responsible for the maintenance of the alkalinity of extracellular fluids?
A) ammonia
B) carbon dioxide
C) ketones such as acetoacetate
D) lactic acid
E) phosphoric acid

Question

Quizplus · Accepted Answer

Carbon dioxide is removed from the body through respiration, and its regulation is crucial for maintaining blood pH. CO2 combines with water to form carbonic acid, which dissociates into bicarbonate and hydrogen ions, affecting pH balance. The vast majority of metabolic acid excretion is in the form of the volatile acid, CO₂, which is removed via the lungs. Much smaller quantities of nonvolatile acids must be excreted in the urine. Within erythrocytes, metabolically produced CO₂ is combined with H₂O forming carbonic acid, which then ionizes to form a bicarbonate ion and a proton. The protons bind to hemoglobin displacing O₂, which not only provides the necessary oxygen for metabolism but also results in increased CO₂ removal. During periods of increased acidity, referred to as metabolic acidosis, chemoreceptors sense a deranged acid-base balance and compensate by increasing respiration rate, hyperventilation, to increase the rate of CO₂ removal.

During the Course of Normal Cellular Metabolism, the Body Generates