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General Physiology

Acid-base balance Practice Questions

37 free Acid-base balance practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.

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Question 1 of 37 Medium

Normal arterial blood pH in humans is approximately:

  1. A 7.00
  2. B 7.20
  3. C 7.40
  4. D 7.60

Correct answer: 7.40

Arterial blood pH is tightly regulated around 7.40. Small deviations can significantly affect enzyme activity and cellular function.

Question 2 of 37 Medium

The primary buffer system in extracellular fluid is the:

  1. A Phosphate buffer system
  2. B Plasma protein buffer system
  3. C Intracellular hemoglobin buffer system
  4. D Bicarbonate buffer system

Correct answer: Bicarbonate buffer system

The bicarbonate buffer system is the most important extracellular buffer. It works in conjunction with the lungs and kidneys to regulate pH.

Question 3 of 37 Medium

Acidosis is defined as arterial blood pH:

  1. A Above 7.45
  2. B Below 7.35
  3. C Between 7.35 and 7.45
  4. D Below 7.50

Correct answer: Below 7.35

Acidosis occurs when blood pH falls below 7.35. It can impair cardiovascular and nervous system function.

Question 4 of 37 Medium

Respiratory acidosis is primarily caused by:

  1. A Loss of bicarbonate
  2. B Excess acid production
  3. C Hypoventilation
  4. D Renal failure

Correct answer: Hypoventilation

Hypoventilation leads to CO₂ retention. Increased CO₂ raises carbonic acid levels, lowering blood pH.

Question 5 of 37 Medium

The main compensatory response to respiratory acidosis involves the:

  1. A Lungs increasing ventilation
  2. B Kidneys excreting hydrogen ions
  3. C Intestines absorbing bicarbonate
  4. D Blood buffering proteins only

Correct answer: Kidneys excreting hydrogen ions

The kidneys compensate by increasing hydrogen ion excretion and bicarbonate reabsorption. This helps restore pH toward normal.

Question 6 of 37 Medium

Metabolic acidosis is characterized by a primary decrease in:

  1. A Carbon dioxide
  2. B Hydrogen ions
  3. C Bicarbonate
  4. D Oxygen

Correct answer: Bicarbonate

Metabolic acidosis results from loss of bicarbonate or accumulation of acids. This lowers blood pH.

Question 7 of 37 Medium

Which condition is a common cause of metabolic acidosis?

  1. A Hyperventilation
  2. B Diabetic ketoacidosis
  3. C Chronic lung disease
  4. D High altitude exposure

Correct answer: Diabetic ketoacidosis

Diabetic ketoacidosis leads to accumulation of organic acids. This consumes bicarbonate and lowers blood pH.

Question 8 of 37 Medium

The primary compensatory mechanism for metabolic acidosis is:

  1. A Renal bicarbonate excretion
  2. B Increased ventilation
  3. C Decreased hydrogen ion secretion
  4. D Reduced protein buffering

Correct answer: Increased ventilation

The lungs compensate by increasing ventilation to blow off CO₂. This reduces carbonic acid concentration.

Question 9 of 37 Medium

Respiratory alkalosis most commonly results from:

  1. A Hypoventilation
  2. B Renal failure
  3. C Hyperventilation
  4. D Loss of gastric acid

Correct answer: Hyperventilation

Hyperventilation causes excessive CO₂ loss. This reduces carbonic acid and raises blood pH.

Question 10 of 37 Medium

Which condition is associated with metabolic alkalosis?

  1. A Diarrhea
  2. B Renal tubular acidosis
  3. C Prolonged vomiting
  4. D Lactic acidosis

Correct answer: Prolonged vomiting

Prolonged vomiting leads to loss of gastric acid. This increases bicarbonate concentration, causing metabolic alkalosis.

Question 11 of 37 Medium

The Henderson-Hasselbalch equation relates blood pH to:

  1. A Dissolved carbon dioxide and oxygen tension
  2. B Bicarbonate and carbon dioxide
  3. C Hydrogen and chloride ions
  4. D Sodium and potassium

Correct answer: Bicarbonate and carbon dioxide

The equation describes pH as a function of bicarbonate concentration and CO₂ partial pressure. It explains acid-base regulation.

Question 12 of 37 Medium

Which buffer system is most important inside cells?

  1. A Bicarbonate buffer
  2. B Phosphate buffer
  3. C Hemoglobin buffer
  4. D Ammonia buffer

Correct answer: Phosphate buffer

The phosphate buffer system plays a major role intracellularly. It helps resist pH changes within cells.

Question 13 of 37 Medium

Hemoglobin contributes to acid-base balance primarily by:

  1. A Binding oxygen only
  2. B Acting as a strong acid
  3. C Buffering hydrogen ions
  4. D Transporting bicarbonate directly

Correct answer: Buffering hydrogen ions

Hemoglobin buffers hydrogen ions released during CO₂ transport. This helps maintain blood pH.

Question 14 of 37 Medium

Which organ is primarily responsible for long-term regulation of acid-base balance?

  1. A Lungs
  2. B Kidneys
  3. C Liver
  4. D Heart

Correct answer: Kidneys

The kidneys regulate acid-base balance by excreting hydrogen ions and adjusting bicarbonate levels. This provides long-term control.

Question 15 of 37 Medium

Renal excretion of hydrogen ions occurs mainly in the:

  1. A Proximal convoluted tubule exclusively
  2. B Descending limb of the loop of Henle
  3. C Distal tubule and collecting duct
  4. D Glomerular filtration membrane

Correct answer: Distal tubule and collecting duct

The distal tubule and collecting duct actively secrete hydrogen ions. This process is essential for acid elimination.

Question 16 of 37 Medium

Which substance allows the kidney to excrete acid without excessively lowering urine pH?

  1. A Bicarbonate
  2. B Ammonia
  3. C Chloride
  4. D Phosphate only

Correct answer: Ammonia

Ammonia buffers hydrogen ions in the tubular fluid. This allows excretion of acid as ammonium.

Question 17 of 37 Medium

In uncompensated metabolic acidosis, arterial blood gases show:

  1. A Low pH and high CO₂
  2. B Low pH and low bicarbonate
  3. C High pH and low CO₂
  4. D Normal pH with low bicarbonate

Correct answer: Low pH and low bicarbonate

The primary disturbance is reduced bicarbonate. This leads to decreased pH before respiratory compensation occurs.

Question 18 of 37 Medium

Which acid-base disorder is characterized by elevated bicarbonate and elevated pH?

  1. A Respiratory acidosis
  2. B Respiratory alkalosis
  3. C Metabolic acidosis
  4. D Metabolic alkalosis

Correct answer: Metabolic alkalosis

Metabolic alkalosis involves excess bicarbonate. This raises blood pH above normal.

Question 19 of 37 Medium

Hypercapnia refers to increased levels of:

  1. A Oxygen
  2. B Bicarbonate
  3. C Carbon dioxide
  4. D Hydrogen ions only

Correct answer: Carbon dioxide

Hypercapnia indicates elevated carbon dioxide in blood. It commonly leads to respiratory acidosis.

Question 20 of 37 Medium

Which of the following best describes complete compensation of an acid-base disorder?

  1. A pH returns fully to normal range
  2. B Primary disturbance is eliminated
  3. C Both pH and primary variable are abnormal
  4. D No compensatory mechanisms are active

Correct answer: pH returns fully to normal range

Complete compensation restores blood pH to the normal range. The primary disturbance remains but is counterbalanced.

Question 21 of 37 Medium

The Henderson-Hasselbalch equation expresses pH as a function of which two variables?

  1. A Bicarbonate and oxygen
  2. B Partial pressures of carbon dioxide and oxygen
  3. C Bicarbonate and carbon dioxide
  4. D Sodium and potassium

Correct answer: Bicarbonate and carbon dioxide

The Henderson-Hasselbalch equation relates pH to the ratio of bicarbonate (HCO3−) to dissolved carbon dioxide (CO2). This ratio determines the acid-base status of blood.

Question 22 of 37 Medium

Which organ plays the most important role in long-term regulation of acid-base balance?

  1. A Lungs
  2. B Kidneys
  3. C Pancreas
  4. D Heart

Correct answer: Kidneys

The kidneys regulate acid-base balance by excreting hydrogen ions and reabsorbing bicarbonate. This provides long-term control compared to rapid respiratory adjustments.

Question 23 of 37 Medium

Respiratory acidosis is most commonly caused by:

  1. A Hyperventilation
  2. B Hypoventilation
  3. C Excess bicarbonate
  4. D Dehydration

Correct answer: Hypoventilation

Hypoventilation leads to retention of CO2, increasing carbonic acid and lowering blood pH. This results in respiratory acidosis.

Question 24 of 37 Medium

Which condition is characterized by decreased pH and decreased bicarbonate concentration?

  1. A Respiratory alkalosis
  2. B Metabolic alkalosis
  3. C Metabolic acidosis
  4. D Respiratory acidosis

Correct answer: Metabolic acidosis

Metabolic acidosis involves a primary decrease in bicarbonate, leading to a reduction in blood pH. It is commonly seen in conditions like diabetic ketoacidosis.

Question 25 of 37 Medium

Which acid-base disorder is characterized by elevated pH and decreased CO2?

  1. A Respiratory acidosis
  2. B Respiratory alkalosis
  3. C Metabolic acidosis
  4. D Metabolic alkalosis

Correct answer: Respiratory alkalosis

Respiratory alkalosis is the only disorder that pairs a high pH with a low CO2: hyperventilation blows off CO2, carbonic acid falls and pH rises. Respiratory acidosis is its mirror image, with CO2 retained and pH low. Metabolic acidosis also shows a low CO2, but only as respiratory compensation for an acidic pH. Metabolic alkalosis raises pH too, yet CO2 rises as breathing slows to compensate.

Question 26 of 37 Medium

Which intracellular buffer system is most significant?

  1. A Bicarbonate
  2. B Phosphate buffer
  3. C Protein buffers
  4. D Carbonic acid

Correct answer: Protein buffers

Protein buffers, including intracellular proteins, play a major role in buffering inside cells. They can accept or donate hydrogen ions.

Question 27 of 37 Medium

The normal arterial blood pH range is approximately:

  1. A 6.80–7.00
  2. B 7.00–7.20
  3. C 7.35–7.45
  4. D 7.50–7.70

Correct answer: 7.35–7.45

Normal arterial pH ranges from 7.35 to 7.45. Values outside this range indicate acid-base disturbances.

Question 28 of 37 Medium

Which mechanism is the primary compensation for metabolic acidosis?

  1. A Decreased ventilation
  2. B Increased renal bicarbonate excretion
  3. C Increased ventilation
  4. D Decreased renal acid excretion

Correct answer: Increased ventilation

In metabolic acidosis, the body compensates by increasing ventilation to eliminate CO2. This reduces carbonic acid and raises pH.

Question 29 of 37 Medium

Hypercapnia refers to an increase in:

  1. A Oxygen levels
  2. B Carbon dioxide levels
  3. C Bicarbonate levels
  4. D Hydrogen ion concentration

Correct answer: Carbon dioxide levels

Hypercapnia is the accumulation of carbon dioxide in the blood. It is commonly associated with respiratory acidosis.

Question 30 of 37 Medium

Which renal process generates new bicarbonate ions?

  1. A Glomerular filtration
  2. B Excretion of ammonium ions
  3. C Tubular secretion of sodium
  4. D Potassium reabsorption

Correct answer: Excretion of ammonium ions

Ammonium excretion in the kidneys leads to the generation of new bicarbonate. This helps maintain acid-base balance.

Question 31 of 37 Medium

Which condition is commonly associated with metabolic alkalosis?

  1. A Diarrhea
  2. B Vomiting
  3. C Renal failure
  4. D Lactic acidosis

Correct answer: Vomiting

Vomiting leads to loss of gastric acid (HCl), resulting in increased bicarbonate and metabolic alkalosis. It is a common clinical cause.

Question 32 of 37 Medium

Which buffer system is most important in red blood cells?

  1. A Phosphate buffer
  2. B Protein buffer
  3. C Bicarbonate buffer
  4. D Hemoglobin buffer

Correct answer: Hemoglobin buffer

Hemoglobin acts as an important buffer in red blood cells by binding hydrogen ions. It plays a key role in transporting CO2.

Question 33 of 37 Medium

Respiratory alkalosis is most likely caused by:

  1. A Hypoventilation
  2. B Renal failure
  3. C Sedative overdose
  4. D Hyperventilation

Correct answer: Hyperventilation

Hyperventilation leads to excessive loss of CO2, decreasing carbonic acid and increasing pH. This results in respiratory alkalosis.

Question 34 of 37 Medium

Which renal mechanism helps excrete hydrogen ions without excessively lowering urine pH?

  1. A Ammonia buffer system
  2. B Bicarbonate excretion
  3. C Glucose filtration
  4. D Protein reabsorption

Correct answer: Ammonia buffer system

The ammonia buffer system allows hydrogen ions to be excreted as ammonium, preventing excessive acidification of urine. This is essential for acid-base balance.

Question 35 of 37 Medium

Which parameter primarily reflects the metabolic component of acid-base balance?

  1. A Partial pressure of oxygen
  2. B Partial pressure of carbon dioxide
  3. C Hemoglobin level
  4. D Bicarbonate concentration

Correct answer: Bicarbonate concentration

Bicarbonate concentration reflects the metabolic component of acid-base balance. Changes in HCO3− indicate metabolic disturbances.

Question 36 of 37 Medium

Complete compensation of an acid-base disorder means:

  1. A pH remains abnormal
  2. B Primary disorder is corrected
  3. C CO2 levels normalize only
  4. D pH returns to normal range

Correct answer: pH returns to normal range

Complete compensation occurs when the pH returns to the normal range despite the underlying disorder. However, other parameters may still be abnormal.

Question 37 of 37 Medium

Which change occurs in respiratory acidosis?

  1. A Increased bicarbonate
  2. B Decreased CO2
  3. C Decreased bicarbonate
  4. D Increased oxygen

Correct answer: Increased bicarbonate

In respiratory acidosis, CO2 retention leads to increased bicarbonate as a compensatory mechanism. The kidneys retain bicarbonate to buffer excess acid.

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