In metabolism, which parameter is determined by the respiratory effect?

• A. Determines the amount of CO2 exhaled with each breath
• B. Determines oxygen uptake per breath
• C. Determines pH of blood
• D. Determines tidal volume

Answer: (A)

The key idea is that ventilation directly controls how much CO2 the body can remove. Metabolism constantly produces CO2, and the respiratory system adjusts breathing to expel it. The parameter directly determined by this respiratory effect is the amount of CO2 exhaled with each breath—more ventilation means more CO2 is blown off, less ventilation means CO2 accumulates in the blood. Oxygen uptake per breath depends on gas diffusion and oxygen delivery, not the direct impact of ventilation on CO2 elimination. Blood pH is influenced by CO2 levels, but it’s a consequence of the CO2 balance rather than a per-breath parameter set by ventilation. Tidal volume is a ventilatory measure that affects how much air moves per breath, but it is not the specific per-breath outcome determined by the respiratory effect on CO2 removal.