Buna is a census-designated place in Jasper County, Texas, United States. The population was 2,142 at the 2010 census.
Gas Exchange. Gas exchange is the process by which oxygen and carbon dioxide (the respiratory gases) move in opposite directions across an organism's respiratory membranes, between the air or water of the external environment and the body fluids of the internal environment.
Gas exchange is the uptake of molecular oxygen (O2) from the environment and the discharge of carbon dioxide (CO2) to the environment. 1  While often called respiration, this process is distinct from, but linked to, the production of ATP in cellular respiration.