Cellulose forms microfibrils which is important for primary and secondary cell wall - Phase 1.
Phase 2 = Matrix
The matrix involves hemicellulose and pectin
Hemicellulose is a group of heterogenous that is cross linked with cellulose from microfibrils that contribute to the structure of cellulose.
Pectin is gel-likepolysaccharides that fill the spaces between cellulose microfibres and provides primary flexibility and retainswater. They are also negatively charged and branched
Protein extensin has a rough amino acid sequence and the extensibility can be controlled by extensin cross linking of pectin and cellulose
Cross linking pectin and cellulose will:
dehydrate cell wall
reduces extensibility
increases strength
Exocytosis transports material out of the cell or delivers it out the cell surface or releases extracellular matrix proteins.
Synthesis of the primary cell wall
the cellulose-producing rosettes move parallel to the cortical microtubules.
Regulating cell is called cell morphology
Cell morphology is the orientation of cellulose microfibrils influences cell morphology.
They are randomly oriented, where they expand in all directions
They have right angles to the long-axis of the cell
The cell wall provides structural support by the protoplast pushing against the cell wall and so the cells become more rigid. Water loss reduces the protoplast volume, which wilting occurs.
The cell wall prevents excessive water uptake as when water enters the cell wall by osmosis, the protoplast pushes and expands against the cell wall. The pressure from this limits the amount of water taken up.
Vacuole structure
It is an organelle surrounded by a single membrane. They are highly selective and controls what comes in and out of the vacuole
Vacuoles regulate the shape by the high concentrations of solutes inside.
Not all plants have a secondary cell wall. This is produced after the cell growth as stopped. They are thicker and stronger than the primary cell wall and provides more structural support.
The secondary cell wall is made up of multiple layered cellulose microfibrils. Microfibrils in each layer have different orientations and strengthens the wall.
Chemical characteristics of secondary cell wall
More cellulose
Less pectin
Lignin
Lignin is the second most important organic macromolecule and a complex polymer. It adds strength and rigidity to the secondary cell wall and acts to exclude water.
The plasmodesmata, the intercellularconnects and enables cell to cell communication. it is continuous and is small enough to prevent organelle movements. They also allow the free exchange of small molecules.