Oxygen and carbon dioxide are exchanged in the lungs and through all cell membranes by:
a. Active transport
b. Diffusion
c. Filtration
d. Osmosis

Verified step by step guidance

1. Understand the process of gas exchange in the lungs and across cell membranes, which involves the movement of oxygen and carbon dioxide molecules between areas of different concentrations.
2. Recall that active transport requires energy to move substances against their concentration gradient, which is not typical for gases like oxygen and carbon dioxide during exchange.
3. Consider diffusion, which is the passive movement of molecules from an area of higher concentration to an area of lower concentration, a process that fits how gases move in the lungs and cells.
4. Evaluate filtration, which involves the movement of water and solutes through a membrane due to pressure differences, generally not applicable to gas exchange.
5. Review osmosis, which specifically refers to the movement of water across a semipermeable membrane, and is not the mechanism for gas exchange.

Key Concepts

Diffusion

Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration. In the lungs and across cell membranes, oxygen and carbon dioxide move by diffusion, allowing gas exchange without energy expenditure.

Active Transport

Active transport is the energy-dependent process where molecules move against their concentration gradient using cellular energy (ATP). It is not typically involved in the exchange of gases like oxygen and carbon dioxide in the lungs.

Osmosis and Filtration

Osmosis is the diffusion of water across a semipermeable membrane, while filtration involves movement of fluids through membranes driven by pressure differences. Neither process primarily facilitates gas exchange in the lungs or cells.