Cellular Transport Mechanisms

Diffusion-
Diffusion involves the movement of atoms across the cytolemma from a region of higher concentration to a region of lower concentration. Atoms move across the cell membrane by by going between the lipid molecules that make up the cell membrane. Small atoms diffuse the easiest across the membrane. No outside chemical energy is needed for simple diffusion.

Facilitated Diffusion-

Diffusion is facilitated by cell membrane proteins that provide a way for atoms or molecules to more easily diffuse across the membrane.




Osmosis-

Osmosis is the simple diffusion of water molecules across a semipermeable membrane. It occurs when the concentration of solutes in the solution on the two sides of a semipermeable membrane are different moves from a solution with a higher water concentration to a solution with lower water concentration.

Active Transport-

Chemical energy in the form of ATP is used to begin this process. A membrane carrier is used and the direction can be from high to low concentration or from low to high concentration. Active transport can enable a cell to move items across the membrane against a concentration gradient.