CO2 diffuses more easily through the respiratory membrane than O2 because it is
**Core Concept**
The facilitation of CO2 diffusion through the respiratory membrane is primarily due to the higher solubility of carbonic acid in blood compared to oxygen. This difference in solubility is a result of the chemical properties of CO2 and O2.
**Why the Correct Answer is Right**
CO2 is a weak acid that readily reacts with water in the blood to form carbonic acid (H2CO3), which dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+). This reaction increases the concentration of CO2 in the bloodstream, allowing it to diffuse more easily through the respiratory membrane. In contrast, oxygen is a smaller, non-reactive molecule that does not readily form complexes with water or other molecules, making it less soluble in blood. Additionally, the presence of hemoglobin in red blood cells binds to CO2, facilitating its transport and diffusion through the respiratory membrane.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not provide a scientifically supported reason for the increased diffusion of CO2 through the respiratory membrane.
**Option B:** This option is incorrect as it does not accurately describe the properties of CO2 or its reaction with water in the bloodstream.
**Option C:** This option is incorrect as it does not provide a relevant explanation for the increased diffusion of CO2 through the respiratory membrane.
**Clinical Pearl / High-Yield Fact**
The Bohr effect describes the decrease in oxygen binding affinity of hemoglobin in response to increased CO2 levels, which facilitates the diffusion of CO2 through the respiratory membrane. This is a crucial concept in understanding respiratory physiology and gas exchange.
**Correct Answer: C. Its reaction with water to form carbonic acid increases its solubility in blood.**