According to the oxygen-hemoglobin dissociation curve, what happens as the partial pressure of oxygen increases?
Oxygen binds less effectively to hemoglobin
Carbon dioxide displaces oxygen from hemoglobin
Hemoglobin is unable to transport oxygen
A greater number of oxygen molecules bind to heme
The Correct Answer is D
A. Oxygen binds less effectively to hemoglobin: As the partial pressure of oxygen (PaO₂) increases, oxygen actually binds more effectively to hemoglobin, not less. The affinity of hemoglobin for oxygen rises as more oxygen molecules occupy heme sites, demonstrating cooperative binding, which is the basis of the sigmoidal shape of the dissociation curve.
B. Carbon dioxide displaces oxygen from hemoglobin: Carbon dioxide can influence oxygen release through the Bohr effect, where increased CO₂ and H⁺ lower hemoglobin’s affinity for oxygen. However, when PaO₂ increases, oxygen loading occurs in the lungs, and CO₂ does not displace oxygen under these conditions.
C. Hemoglobin is unable to transport oxygen: Hemoglobin’s ability to transport oxygen is directly dependent on its oxygen saturation and PaO₂. Higher partial pressures enhance oxygen binding, enabling hemoglobin to transport more oxygen to tissues rather than impairing its transport function.
D. A greater number of oxygen molecules bind to heme: As PaO₂ rises, more oxygen molecules attach to the available heme sites on hemoglobin. This cooperative binding leads to higher oxygen saturation, allowing hemoglobin to efficiently pick up oxygen in the lungs and deliver it to tissues, which is reflected in the steep portion of the oxygen-hemoglobin dissociation curve.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. It increases: When oxygen demand rises, such as during exercise or metabolic stress, chemoreceptors in the carotid bodies and medulla detect lower oxygen levels and higher carbon dioxide levels. The respiratory center in the brainstem responds by increasing the rate and depth of breathing to enhance oxygen intake and carbon dioxide elimination, meeting the body’s metabolic needs.
B. It decreases: A decrease in respiratory rate would reduce oxygen intake and carbon dioxide removal, worsening hypoxia and hypercapnia. This response is contrary to physiological needs during increased oxygen demand and would be maladaptive.
C. It remains the same: Maintaining a constant respiratory rate would be insufficient to meet elevated oxygen demands, leading to tissue hypoxia. The body naturally adjusts ventilation to match metabolic requirements rather than keeping it unchanged.
D. It stops: Complete cessation of breathing, or apnea, prevents oxygen delivery and carbon dioxide removal, which is life-threatening. The body automatically increases ventilation rather than stopping it when oxygen demand rises.
Correct Answer is {"dropdown-group-1":"D"}
Explanation
A. Glucose: Glucose is a primary energy source for cellular metabolism but is not directly involved in gas exchange in the lungs. Ventilation-perfusion (V/Q) coupling does not influence glucose uptake or distribution, as this process is unrelated to pulmonary oxygenation or CO₂ elimination.
B. Hydrogen: Hydrogen ions are involved in acid-base balance and blood pH regulation but are not directly carried or exchanged through ventilation-perfusion matching. Their levels are influenced indirectly by CO₂ removal but are not the primary target of pulmonary gas exchange.
C. Nitrogen: Nitrogen is an inert gas in the lungs and does not participate in metabolic gas exchange. V/Q coupling does not optimize nitrogen uptake or removal, as it remains largely unchanged in pulmonary circulation.
D. Oxygen: Proper ventilation-perfusion coupling ensures that alveoli receive sufficient air (ventilation) relative to the blood flow (perfusion) in surrounding capillaries. This optimization maximizes oxygen uptake into the blood and facilitates carbon dioxide removal, maintaining effective gas exchange and supporting tissue oxygenation.
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