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# Exchange of Gases The steady state volume of oxygen consumed by body cells is equal to the volume of oxygen entering the blood in the lungs per unit time. Similarly, the rate of carbon dioxide production by body cells entering the systemic blood equals the rate at which it leaves the blood in th...

# Exchange of Gases The steady state volume of oxygen consumed by body cells is equal to the volume of oxygen entering the blood in the lungs per unit time. Similarly, the rate of carbon dioxide production by body cells entering the systemic blood equals the rate at which it leaves the blood in the lungs. However, the amounts are not always equal; this depends on which nutrients are used for energy. The **respiratory quotient (RQ)** describes the ratio of CO2 produced to O2 consumed. * RQ = 1 for carbohydrates * RQ = 0.7 for fats * RQ = 0.8 for protein * For a mixed diet, RQ is approximately 0.8 (meaning for every 10 molecules of O₂ consumed, 8 molecules of CO₂ are produced). ## Partial Pressures of Gases and Mixtures 1. **Dalton's Law:** In a mixture of gases, the pressure exerted by each gas is independent of the pressures exerted by the other gases. Total pressure is the sum of individual gas pressures. Pressure depends on temperature, concentration and altitude. 2. **Henry's Law:** When a liquid is exposed to air containing a gas, the amount of gas dissolved in the liquid is directly proportional to the partial pressure of that gas and the solubility of the gas.