Functions

It maintains turgor pressure within the cell which gives plant cells their characteristic polyhedral shape.
They serve as skeletons for both the cell and the organism.
Protects against damage from abrasion and pathogens
Mediates cell-cell interactions.

Composition

They contain a fibrous element embedded in a non-fibrous gel-like matrix.
Cellulose makes up the fibrous elements of the cell wall. They are organized into microfibrils that make the cell wall rigid and add tensile strength.
- Microfibrils are often organized in cross-hatching fashion, where the microfibrils of one layer are oriented perpendicular to those of adjacent layers.
- Cellulose is synthesized via cellulose synthase on the cell surface.
The cell matrix consists of the non-fibrous parts which are synthesized within the cytoplasm
- Hemicellulose - branched polysaccharides that bind and cross-link microfibrils to form a resilient network
- Pectins - negatively charged glacturonic acid-containing polysaccharides. They form a hydrated gel that fills the space of the fibrous elements.
- There are proteins that facilitate dynamic activities
  - Expansins - facilitates relaxation of the cell wall at certain sites.
  - Kinases - transmit signals from cell-wall to cytoplasm.

They arise from a thin cell plate which then matures by incorporate additional materials.
Primary Cell Walls are the flexible walls of growing cells. Secondary Cell Walls are the thicker walls found in mature plant cells.
- The transition from primary to secondary occurs due to an increase in cellulose.
- They often incorporate lignin for additional structural support.