They move to an area where they are less concentrated
Explanation:
In a cell the surface that separates the system from the surrounding environment is the cell membrane and the exchange of substances between the cell and the medium must occur through this membrane. This exchange is essential to maintain the integrity of the cell and to provide the different chemical species necessary for the metabolic processes that occur permanently within it. As we saw, substances move driven by their gradient of chemical or electrochemical potential. Every substance is formed by molecules that have a certain amount of thermal energy that is indicative of their spontaneous movements, a result of thermal movement is diffusion. A large part of the passage of molecules through the cell membrane is produced by simple diffusion. When one molecule is more concentrated on one side of the membrane than on the other and the membrane is permeable to it, there is a tendency for the molecule to diffuse through the membrane in favor of its concentration gradient. This dezplacement occurs without external energy expenditure (passive transport).
An important example is the oxygen uptake of a cell by performing cellular respiration. Dissolved oxygen diffuses into the cell through the cell membrane. As cellular respiration consumes the entering O2, diffusion within the cell will continue because the concentration gradient favors movement in that direction. The same happens, but in the opposite direction, with carbon dioxide. Then you can see the process in the following animation.
In simple diffusion through a biological membrane, small non-polar solute molecules (no charge) move directly through the membrane in favor of their concentration gradient. Oxygen and carbon dioxide can diffuse rapidly through the membrane. The simple diffusion rate is directly related to the solute concentration; The more concentrated the solute, the faster the diffusion.
