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3.3 Gas Exchange — Test 1
Q1. Which enzyme catalyses the conversion of bicarbonate back to CO₂ in the pulmonary capillaries (and CO₂ to bicarbonate in tissues)?✓ Carbonic anhydrase
Q2. The chloride shift (Hamburger phenomenon) is essential for the transport of:✓ Carbon dioxide
Q3. Hamburger's phenomenon is also known as the:✓ Chloride shift
Q4. Which factor will shift the oxygen–haemoglobin dissociation curve to the right (lower affinity)?✓ Increased hydrogen ion concentration (lower pH)
Q5. The partial pressure of CO₂ is highest in the:✓ Systemic (tissue) venous blood
Q6. Oxygen moves from the alveoli into the blood because it diffuses from:✓ High partial pressure to low partial pressure
Q7. The gas exchange between alveolar air and blood (external respiration) occurs by:✓ Simple diffusion across the alveolar–capillary membrane
Q8. In tissues, oxygen is released from haemoglobin more readily because the tissue environment is:✓ Warm, acidic and high in CO₂
Q9. Most carbon dioxide is transported in the blood as:✓ Bicarbonate ions
Q10. Carbonic anhydrase, which speeds CO₂ handling, is located mainly in the:✓ Red blood cells
Q11. If lung pO₂ is 100 mmHg (Hb ~97% saturated) and tissue pO₂ is 25 mmHg (Hb ~45% saturated), the approximate oxygen released is:✓ About 50%
Q12. The metabolic (non-respiratory) functions of the lung include:✓ Converting angiotensin I to angiotensin II and inactivating some hormones
Q13. Prostaglandins circulating in the blood are rapidly inactivated mainly in the:✓ Lungs
Q14. Internal respiration refers to gas exchange between:✓ Blood and the body tissues
3.3 Gas Exchange — Test 2
Q15. During strenuous exercise, oxygen supply to active muscles increases partly because:✓ The oxygen dissociation curve shifts right, unloading more O₂
Q16. The amount of oxygen carried dissolved in plasma (not bound to haemoglobin) is:✓ Very small (about 1.5% of total O₂)
Q17. At the tissues, the uptake of CO₂ into the blood promotes oxygen release; this interaction is the:✓ Bohr effect
Q18. The driving force for the diffusion of each respiratory gas across the alveolar membrane is its:✓ Partial-pressure gradient
Q19. During hyperventilation, the resulting low CO₂ can cause dizziness because it leads to:✓ Cerebral vasoconstriction from respiratory alkalosis
Q20. Oxygen is carried in the blood mainly:✓ Bound to haemoglobin in red cells
Q21. Carbon dioxide is mainly transported in the blood as:✓ Bicarbonate ions in plasma
Q22. The exchange of gases between alveoli and blood occurs by:✓ Diffusion down partial-pressure gradients
Q23. The oxygen–haemoglobin dissociation curve is S-shaped (sigmoid) because of:✓ Cooperative binding of oxygen to haemoglobin
Q24. A rise in temperature shifts the oxygen dissociation curve:✓ To the right (lower affinity)
Q25. At the tissues, oxygen leaves the blood because tissue oxygen partial pressure is:✓ Lower than in the blood
Q26. The enzyme that speeds the conversion of CO₂ and water to carbonic acid in red cells is:✓ Carbonic anhydrase
Q27. External respiration refers to gas exchange between:✓ Alveoli and the blood
Q28. The chloride shift accompanies CO₂ transport to:✓ Maintain electrical neutrality as bicarbonate leaves red cells