Cellular exchange
Cellular exchange
Definition:
Cellular exchange is the movement of substances in and out of the cell. This occurs through the following processes: Diffusion, osmosis, active transport and facilitated diffusion.
Definition of some terms:
- A solute: This is a substance that dissolves in a solid. g. sugar, salt etc.
- A solvent: This is any liquid in which the solute dissolves. E.g. water, kerosine, alcohol etc
- A solution: It is a uniform mixture formed from a solute and a solvent.
- Concentration gradient: This is the difference between the concentrations of two solutions.
Types of solutions
There are 3 types of solutions: hypertocic, hypotonic and isotonic solutions.
- Hypotonic solution: This is a solution with a lower concentration when compared with another solution or contains a lower number of solute molecules.
- Hypertonic solution: This is a solution with a higher concentration when compared with another solution or contains a higher number of solute molecules.
- Isotonic solution: This is a solution of equal concentration when compared with another solution or contains equal number of solute and solvent molecules.
Definition:
This is the movement of molecules from a region of higher concentration to a region of lower concentration until equilibrium is reached. E.g. when perfume is sprayed a a certain corner in a room, the smell would be gotten at the other end in seconds. The movement of the perfume molecules in air is seen in the diagram below
Osmosis
Definition: This is the movement of water molecules only from a region of higher concentration to a region of lower concentration across a selectively permeable membrane.
Exosmosis and Endosmosis
Endosmosis is the movement of water molecules from the surrounding environment into the cells.
Exosmosis is the movement of water molecules from within cells into the surrounding environment
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