What allows small particles to move through cell membranes?
Is it diffusion?
Yes, diffusion is one of the processes that allows small particles to move through cell membranes. Diffusion is the passive movement of particles from an area of higher concentration to an area of lower concentration. This movement occurs due to the random motion of particles, and it does not require any energy input from the cell.
In the context of a cell membrane, diffusion allows small particles, such as gases (oxygen and carbon dioxide), water (through osmosis), and lipid-soluble molecules, to move across the lipid bilayer. These particles can pass directly through the phospholipid molecules, which make up the cell membrane. Since small particles will naturally move from an area of high concentration to low concentration, they will diffuse across the cell membrane until equilibrium is reached, where the concentrations on both sides are equal.
It is important to note that large molecules, such as proteins or complex ions, cannot passively diffuse through the cell membrane. For their movement, specialized transport mechanisms, such as facilitated diffusion or active transport, are required.