Connect hydrogen ion concentration with pH, then distinguish the roles of buffers, ventilation and renal regulation. These questions explain basic physiology rather than treatment decisions.
8 questions · Estimated 6–8 minutes. Select your answer mentally, then open the explanation to check your reasoning.
Answer: C. 7.35–7.45
Normal arterial blood pH is commonly approximately 7.35–7.45. A value below this range indicates acidemia and a value above it indicates alkalemia. Acidosis and alkalosis refer to processes that tend to lower or raise pH.
Answer: A. Falls by one unit
pH is the negative base-10 logarithm of hydrogen ion activity, often approximated using concentration in introductory physiology. A tenfold increase therefore lowers pH by one unit. The pH scale is logarithmic, not linear.
Answer: D. To limit pH changes by accepting or releasing hydrogen ions
Buffers reduce the size of a pH change by reversibly binding or releasing hydrogen ions. Their capacity is finite. Buffering does not replace the need to eliminate carbon dioxide through the lungs or excrete nonvolatile acid through the kidneys.
Answer: B. Bicarbonate to dissolved carbon dioxide
The Henderson–Hasselbalch relationship links pH to bicarbonate relative to dissolved carbon dioxide. Dissolved carbon dioxide is proportional to its partial pressure. Ventilation regulates carbon dioxide, while the kidneys regulate bicarbonate and acid excretion.
Answer: C. Respiratory acidosis from carbon dioxide retention
Reduced alveolar ventilation causes carbon dioxide retention. The resulting increase in carbon dioxide partial pressure tends to lower pH, producing respiratory acidosis. With time, renal compensation can increase bicarbonate retention and acid excretion.
Answer: D. A primary decrease in bicarbonate
Metabolic acidosis involves a primary reduction in bicarbonate, such as through buffering of an added acid or loss of bicarbonate. Increased ventilation can lower carbon dioxide as compensation. A low bicarbonate value alone is not enough to identify the primary disorder without the rest of the acid–base findings.
Answer: A. Increased alveolar ventilation, lowering carbon dioxide partial pressure
Increased ventilation lowers carbon dioxide and helps move pH toward normal. Compensation does not remove the underlying metabolic cause. A carbon dioxide value outside the expected compensatory range suggests an additional respiratory disorder.
Answer: B. Increasing net acid excretion and adding new bicarbonate to blood
The kidneys can increase acid excretion as ammonium and titratable acid, adding new bicarbonate to blood. They also reclaim filtered bicarbonate. Reclaiming filtered bicarbonate prevents its loss; it is distinct from generating new bicarbonate.