ACIDOSIS AND ALKALOSIS MCQs – 39 MCQs | Kenya MBChB

39 Year 3: Hematopathology exam questions on ACIDOSIS AND ALKALOSIS MCQs for medical students. Includes MCQs, answers, explanations and written questions. Sampl

This MCQ set contains 39 questions on ACIDOSIS AND ALKALOSIS MCQs in the Year 3: Hematopathology unit. Each question includes the correct answer and a detailed explanation for active recall and exam preparation.

Q1: What is the normal pH range of human blood?

  1. A. 7.00-7.20
  2. B. 7.35-7.45
  3. C. 7.50-7.65
  4. D. 6.80-7.00

Correct answer: B – 7.35-7.45

Blood pH is tightly regulated within a narrow range of 7.35 to 7.45. Even slight deviations from this range can have serious health consequences affecting various physiological processes.

Q2: A patient with chronic obstructive pulmonary disease (COPD) has ABG results showing pH 7.28, PaCO2 58 mmHg, and HCO3- 26 mEq/L. What is the primary acid-base disorder?

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

Correct answer: C – Respiratory acidosis

The pH is low (acidosis), PaCO2 is elevated ( 45 mmHg), and HCO3- is normal. This indicates respiratory acidosis caused by inadequate ventilation and CO2 retention, typical in COPD.

Q3: Which buffer system is the PRIMARY extracellular buffer system in the body?

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

Correct answer: C – Bicarbonate buffer system

The bicarbonate buffer system (H2CO3/HCO3-) is the primary extracellular buffer system, particularly in blood plasma, maintaining pH within the normal range of 7.35-7.45.

Q4: A diabetic patient presents with rapid, deep breathing (Kussmaul respirations). Which acid-base disorder is this compensatory mechanism addressing?

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

Correct answer: B – Metabolic acidosis

Kussmaul respirations (rapid, deep breathing) represent respiratory compensation for metabolic acidosis. The body increases ventilation to eliminate CO2, reducing carbonic acid and helping raise blood pH.

Q5: What is the normal range for arterial PaCO2?

  1. A. 20-30 mmHg
  2. B. 35-45 mmHg
  3. C. 50-60 mmHg
  4. D. 60-70 mmHg

Correct answer: B – 35-45 mmHg

Normal arterial PaCO2 is 35-45 mmHg. Values above 45 mmHg indicate respiratory acidosis, while values below 35 mmHg indicate respiratory alkalosis.

Q6: A patient with severe vomiting develops metabolic alkalosis. Which mechanism explains this?

  1. A. Retention of CO2
  2. B. Loss of gastric acid (HCl)
  3. C. Accumulation of lactic acid
  4. D. Renal failure

Correct answer: B – Loss of gastric acid (HCl)

Vomiting causes loss of gastric acid (HCl), leading to metabolic alkalosis due to the loss of hydrogen ions and relative excess of bicarbonate in the blood.

Q7: What is the normal range for serum bicarbonate (HCO3-)?

  1. A. 12-18 mEq/L
  2. B. 18-22 mEq/L
  3. C. 22-26 mEq/L
  4. D. 28-32 mEq/L

Correct answer: C – 22-26 mEq/L

Normal serum bicarbonate is 22-26 mEq/L. Values above 26 mEq/L indicate metabolic alkalosis, while values below 22 mEq/L indicate metabolic acidosis.

Q8: Which enzyme in renal tubular cells catalyzes the reaction between CO2 and water to form carbonic acid?

  1. A. Lactate dehydrogenase
  2. B. Carbonic anhydrase
  3. C. Alkaline phosphatase
  4. D. Creatine kinase

Correct answer: B – Carbonic anhydrase

Carbonic anhydrase catalyzes the reversible reaction between CO2 and water to form carbonic acid (H2CO3), which then dissociates into H+ and HCO3-, playing a crucial role in renal acid-base regulation.

Q9: A patient has ABG results: pH 7.50, PaCO2 30 mmHg, HCO3- 23 mEq/L. What is the diagnosis?

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

Correct answer: D – Respiratory alkalosis

The pH is high (alkalosis), PaCO2 is low (<35 mmHg), and HCO3- is normal. This indicates respiratory alkalosis caused by hyperventilation and excessive CO2 elimination.

Q10: What is the formula for calculating anion gap?

  1. A. Na+ + K+ - Cl
  2. B. Na+ - (Cl- + HCO3-)
  3. C. K+ - (Cl- + HCO3-)
  4. D. Na+ + Cl- - HCO3

Correct answer: B – Na+ - (Cl- + HCO3-)

Anion gap is calculated as Na+ - (Cl- + HCO3-). The normal range is typically 8-12 mEq/L. An increased anion gap suggests metabolic acidosis with unmeasured anions.

Q11: Which condition is characterized by an increased anion gap metabolic acidosis?

  1. A. Diarrhea
  2. B. Renal tubular acidosis
  3. C. Diabetic ketoacidosis
  4. D. Vomiting

Correct answer: C – Diabetic ketoacidosis

Diabetic ketoacidosis causes increased anion gap metabolic acidosis due to accumulation of unmeasured ketone bodies (β-hydroxybutyrate and acetoacetate), which are acids not measured in routine electrolyte panels.

Q12: A patient at high altitude develops dizziness and tingling in the extremities. Which acid-base disorder is most likely?

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

Correct answer: D – Respiratory alkalosis

High altitude causes hyperventilation (to compensate for low oxygen), leading to respiratory alkalosis. Symptoms include dizziness, tingling in extremities, and muscle cramps due to excessive CO2 elimination.

Q13: In the proximal tubule, hydrogen ions are secreted into the tubular lumen primarily in exchange for which ion?

  1. A. Potassium (K+)
  2. B. Sodium (Na+)
  3. C. Chloride (Cl-)
  4. D. Calcium (Ca2+)

Correct answer: B – Sodium (Na+)

In the proximal tubule, hydrogen ions are secreted into the tubular lumen by specialized transporters primarily in exchange for sodium ions through Na+/H+ exchangers.

Q14: Which pharmacological agent inhibits carbonic anhydrase and promotes bicarbonate excretion?

  1. A. Furosemide
  2. B. Acetazolamide
  3. C. Sodium bicarbonate
  4. D. Potassium chloride

Correct answer: B – Acetazolamide

Acetazolamide inhibits carbonic anhydrase, preventing bicarbonate reabsorption in the kidneys and promoting its excretion, leading to metabolic acidosis correction in conditions like metabolic alkalosis.

Q15: A patient with lactic acidosis due to septic shock would most likely present with which type of acid-base disorder?

  1. A. Respiratory acidosis with normal anion gap
  2. B. Metabolic acidosis with increased anion gap
  3. C. Metabolic alkalosis
  4. D. Respiratory alkalosis

Correct answer: B – Metabolic acidosis with increased anion gap

Lactic acidosis from tissue hypoperfusion in septic shock causes metabolic acidosis with increased anion gap due to accumulation of lactate, an unmeasured anion.

Q16: What is the primary role of hemoglobin in acid-base balance?

  1. A. Eliminates CO2 from lungs
  2. B. Acts as intracellular protein buffer binding hydrogen ions
  3. C. Produces bicarbonate in kidneys
  4. D. Regulates aldosterone secretion

Correct answer: B – Acts as intracellular protein buffer binding hydrogen ions

Hemoglobin acts as an intracellular protein buffer by binding with hydrogen ions, helping prevent large fluctuations in pH within red blood cells and contributing to overall buffering capacity.

Q17: A patient with severe diarrhea develops metabolic acidosis. What is the mechanism?

  1. A. Retention of CO2
  2. B. Loss of bicarbonate-rich intestinal fluids
  3. C. Accumulation of ketones
  4. D. Hyperventilation

Correct answer: B – Loss of bicarbonate-rich intestinal fluids

Severe diarrhea causes loss of bicarbonate-rich intestinal fluids, resulting in metabolic acidosis due to decreased bicarbonate levels in the blood without an increased anion gap.

Q18: Which hormone promotes sodium reabsorption and can indirectly influence pH regulation?

  1. A. Antidiuretic hormone (ADH)
  2. B. Aldosterone
  3. C. Parathyroid hormone (PTH)
  4. D. Insulin

Correct answer: B – Aldosterone

Aldosterone promotes reabsorption of sodium and bicarbonate ions in the kidneys, leading to increased blood pH and indirectly influencing acid-base regulation.

Q19: A patient receives excessive intravenous bicarbonate. Which acid-base disorder will likely develop?

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

Correct answer: B – Metabolic alkalosis

Excessive bicarbonate intake causes metabolic alkalosis due to an excess of bicarbonate in the blood, increasing pH above the normal range.

Q20: What compensatory mechanism does the body employ in metabolic alkalosis?

  1. A. Increased ventilation
  2. B. Decreased ventilation to retain CO2
  3. C. Increased renal H+ secretion
  4. D. Decreased renal bicarbonate reabsorption only

Correct answer: B – Decreased ventilation to retain CO2

In metabolic alkalosis, the respiratory system compensates by decreasing ventilation rate to retain CO2, increasing carbonic acid levels and thereby lowering blood pH toward normal.

Q21: Which buffer system is most important in regulating intracellular pH and urine pH?

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

Correct answer: C – Phosphate buffer system

The phosphate buffer system (HPO4²-/H2PO4-) plays a significant role in buffering intracellular fluids and urine, accepting or donating hydrogen ions depending on pH.

Q22: A patient with anxiety disorder hyperventilates during a panic attack. What immediate acid-base change occurs?

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

Correct answer: D – Respiratory alkalosis

Hyperventilation during anxiety causes excessive elimination of CO2, leading to respiratory alkalosis characterized by decreased PaCO2 and increased pH.

Q23: What is the normal range for the anion gap?

  1. A. 2-6 mEq/L
  2. B. 8-12 mEq/L
  3. C. 15-20 mEq/L
  4. D. 22-26 mEq/L

Correct answer: B – 8-12 mEq/L

The normal anion gap is typically 8-12 mEq/L. Values greater than 12 mEq/L suggest metabolic acidosis due to unmeasured anions like lactate, ketones, or toxins.

Q24: Which clinical finding is characteristic of severe metabolic acidosis?

  1. A. Muscle tetany
  2. B. Kussmaul respirations
  3. C. Decreased respiratory rate
  4. D. Hypoventilation

Correct answer: B – Kussmaul respirations

Kussmaul respirations (rapid, deep breathing) are characteristic of severe metabolic acidosis, representing the body's attempt to compensate by eliminating CO2 and raising pH.

Q25: A patient with chronic kidney disease cannot excrete hydrogen ions effectively. Which acid-base disorder develops?

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

Correct answer: B – Metabolic acidosis

Renal failure impairs the kidneys' ability to excrete hydrogen ions and generate bicarbonate, leading to metabolic acidosis due to accumulation of acids.

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