What Is Passive Transport?

If the cell is to carry out process of respiration and protein synthesis, it must obtain supplies of sugar, oxygen and amino acids and it must be able to get rid of waste products that accumulate as a result of these processes.

Passive transport is one of the methods by which cells take up substances through their membranes. It includes the processes of diffusion and osmosis.  Diffusion occurs when the molecules of a dissolved substance are unevenly distributed.

If the cell membrane is permeable to the molecules, the concentrations of either sides of it would eventually become equal, no matter how uneven they were initially. Diffusion could thus account for the movement of oxygen, glucose and amino acid into the cell and water and carbon dioxide out of the cell.

As respiration occurs inside the cell, the concentration of glucose and oxygen would eventually decrease as these substances are used up. There concentration, in the tissue fluid outside the cell would be greater. Therefore, in order to restore balance, these two substances would diffuse into the cell.  Similarly, carbon dioxide and water accumulated inside the cell would diffuse out.

The cell membrane exercises control over what enter and exits a cell. Entries of harmful substance are restricted.