When blood reaches the respiring tissues, haemoglobin
Correct answer: D. releases oxygen and picks up carbon dioxide
- A. releases carbon dioxide and binds more oxygen
- B. is destroyed by the cells
- C. holds its oxygen more tightly
- D. releases oxygen and picks up carbon dioxide
Explanation
Low oxygen pressure and high CO2 in the tissues make haemoglobin surrender oxygen and take on CO2 and H+, reversing what happened in the lungs. One molecule thus shuttles both gases on the same round trip.
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About Human Respiratory System
The human respiratory system conducts air to the alveoli, where oxygen and carbon dioxide exchange occurs across thin respiratory surfaces. Questions cover the nasal passage, trachea, bronchi, lungs, diaphragm and intercostal muscles, ventilation mechanics and gas transport, while distinguishing breathing and gaseous exchange from cellular respiration.
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