This is a passive process, which means it does not need energy. The oxygen diffuses across the partially permeable membrane of the alveoli cells and the capillary wall, into the red blood cells to ...

Transport across membranes All cells are enclosed by a cell membrane, which is selectively permeable. Molecules can move into or out of cells by diffusion and active transport. Cells can gain or ...

The ability to maintain concentration gradients and sometimes move materials against them is vital to cell health and maintenance. Thanks to membrane barriers and transport proteins, the cell can ...