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Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a biological membrane that forms the boundary between an organism and its extracellular environment.
If no bulk flow occurs in an element of length dx, the rates of diffusion of two ideal gases (of similar molar volume) A and B must be equal and opposite, that is =. The partial pressure of A changes by dP A over the distance dx. Similarly, the partial pressure of B changes dP B. As there is no difference in total pressure across the element ...
At the end of each tracheal branch, a special cell provides a thin, moist interface for the exchange of gases between atmospheric air and a living cell. Oxygen in the tracheal tube first dissolves in the liquid of the tracheole and then diffuses across the cell membrane into the cytoplasm of an adjacent cell. At the same time, carbon dioxide ...
The process of breathing does not fill the alveoli with atmospheric air during each inhalation (about 350 ml per breath), but the inhaled air is carefully diluted and thoroughly mixed with a large volume of gas (about 2.5 liters in adult humans) known as the functional residual capacity which remains in the lungs after each exhalation, and ...
Respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. The overall reaction occurs in a series of biochemical steps, some of which are redox reactions. Although cellular respiration is technically a combustion reaction , it is an unusual one because of the slow, controlled release of energy from the series ...
Fick's first law relates the diffusive flux to the gradient of the concentration. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low ...
As oxygen continues to flow down the concentration gradient from areas of higher concentration to areas of lower concentration, it must pass through barriers such as the alveoli walls, capillary walls, capillary blood plasma, red blood cell membrane, interstitial space, other cell membranes, and cell cytoplasm. The partial pressure of oxygen ...
In contrast, paracellular transport is the transfer of substances across an epithelium by passing through an intercellular space between the cells. It differs from transcellular transport, where the substances travel through the cell passing through both the apical membrane and basolateral membrane; Renal physiology. Transcellular transport is ...