What does the term "partial pressure of gas" refer to?

The term "partial pressure of gas" specifically refers to the individual pressure exerted by a particular gas in a mixture, which can also be understood as the concentration of that gas within the mixture. In various scientific contexts, including respiratory physiology, it is important to note that partial pressure contributes to the overall behavior and movement of gases within different systems, such as diffusion in the lungs and circulation.

Partial pressure is derived from the ideal gas law and helps to quantify how much of a specific gas is available or concentrated within a given space, influencing its ability to be absorbed or to diffuse into other environments, such as blood or tissues. This concept is vital for understanding processes like oxygen delivery and carbon dioxide removal in the body, as well as the overall gas exchange in the respiratory system.

The other options address related but distinct concepts; the total pressure of all gases would refer to atmospheric or barometric pressure, while diffusion is influenced by concentrations or gradients, but is not the definition of partial pressure itself.