Membranes

A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, which provides the cell with structural support, protection, and acts as a filtering mechanism. The cell wall also prevents over-expansion when water enters the cell. They are found in plants, bacteria, archaea, fungi, and algae.

A cell membrane regulates what enters and exists the cell.
Active transport - Requires energy to push particles through the membrane. Passive transport - Occurs spontaneously in order to randomly distribute particles through the system and to achieve equilibrium.

The Metapolis Dictionary For Advanced Architecture defines a Membrane as: a thin layer of organic, elastic and resistant tissue which separate two cavities or envelops an organ.


Molecular structure of the primary cell wall in plants.


Scanning electron micrographs of diatoms showing the external appearance of the cell wall