L8 Cell wall

Cell Wall functions

Influence cell morphology, provide structural support, prevent excessive water uptake.

Primary Cell Wall

The first layer of the cell wall, primarily composed of cellulose, pectin, and hemicellulose.

Secondary Cell Wall

Stronger than primary cell wall, provides more strength and structure for specific cell types (eg. water transporting cells). Is only produced after cell growth has stopped.

Secondary cell wall components

More cellulose, less pectin, and lignin. Lignin is like the “filler” molecule.

Microfibrils

Long, ribbon-like structures composed of cellulose that provide strength to the cell wall.

Plasmodesmata

Intercellular connections in plants that allow communication and transport of materials between cells.

Turgor Pressure

Pressure exerted by the fluid contents of a cell against the cell wall, maintaining cell rigidity. Opposes osmosis.

Vacuole

A membrane-bound organelle in plant cells that stores water and maintains turgor pressure. (highly selective)

Hemicellulose

A heterogeneous group of polysaccharides found in the cell wall, providing rigidity and structure.

Pectin

Branching polysaccharides that bind water, providing gel-like properties to the cell wall.

Extensin

A protein that cross-links polysaccharides in the cell wall, regulating cell expansion and strength.

What synthesises cellulose?

Rossetes

Cell morphology

Influenced by orientation of microfibrils (cellulose).

randomly orriented= cell will expand equally in all directions

Oriented perpindicular to long axis of cell= will grow in length, but not width.

Protoplasts

Maintain structure by pushing against the cell wall. Need hydration to work. relates to turgor pressure