What process is used for gas exchange in alveoli?

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Multiple Choice

What process is used for gas exchange in alveoli?

Gas exchange in the alveoli happens by diffusion, the passive movement of gas molecules down their partial pressure gradients across the respiratory membrane. Oxygen moves from the air in the alveoli (higher PO2) into the blood (lower PO2), while carbon dioxide moves from the blood (higher PCO2) into the alveolar air (lower PCO2) to be exhaled. The respiratory membrane is extremely thin and has a large surface area, which speeds diffusion and allows rapid equilibration of gas concentrations between air and blood. Oxygen and carbon dioxide diffuse without the input of energy, driven simply by these gradients and the inherent solubility and mobility of the gases. Other processes don’t account for this gas exchange. Osmosis involves water movement across membranes, not gases. Active transport requires energy and moves substances against gradients, not down them. Filtration involves bulk movement of fluid through capillary walls, driven by pressure differences, not the diffusion of gases.

Gas exchange in the alveoli happens by diffusion, the passive movement of gas molecules down their partial pressure gradients across the respiratory membrane. Oxygen moves from the air in the alveoli (higher PO2) into the blood (lower PO2), while carbon dioxide moves from the blood (higher PCO2) into the alveolar air (lower PCO2) to be exhaled. The respiratory membrane is extremely thin and has a large surface area, which speeds diffusion and allows rapid equilibration of gas concentrations between air and blood. Oxygen and carbon dioxide diffuse without the input of energy, driven simply by these gradients and the inherent solubility and mobility of the gases.

Other processes don’t account for this gas exchange. Osmosis involves water movement across membranes, not gases. Active transport requires energy and moves substances against gradients, not down them. Filtration involves bulk movement of fluid through capillary walls, driven by pressure differences, not the diffusion of gases.

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