cell wall is a rigid and dense shell above the cytoplasmic membrane.This element is characteristic for cells of bacteria, fungi and plants.In addition to protecting cells, performs a hard shell and a number of other equally important functions.
cell wall: the basics
cell wall of each organism has a number of features.For example, in bacteria it consists essentially of murein.Incidentally, the bacterial strains are divided into two types - gram and gram - precisely because of the peculiarities of the structure of the rigid shell.This determines the sensitivity to antibiotics.
If we talk about the cell walls of fungi, they are considered to be major components of chitin and glucans.But algae shell may consist of various polysaccharides - mostly glucose and its compounds.By the way, the composition of the cell wall of algae is very important taxa.It is necessary to recall the group of diatoms, whose members own wall synthesized from silica.
plant cell wall and its function
Principles rigid structure of the cell membrane is most convenient to study the example of a plant cell.Although mechanical protection - this is one of the most important functions of the cell wall, it has a far greater significance:
- provides mechanical and chemical resistance of the cell;
- prevents rupture the cells in hypotonic medium;
- cell wall is an ion exchanger and as it is carried through the uptake and release of ions;
- takes part in the transport of organic compounds.
structure of the cell wall
The plant wall is divided into three main components: the frame matrix and incrusting substance.
frame plant cell wall consists of cellulose.Owing to the formation of hydrogen bonds, cellulose molecules form strong microfibrils that are immersed in the ground substance, or matrix.
Matrix cell wall is about 60% of its total mass.It fills the space between the microfibrils and creates strong bonds between the macromolecules, provides elasticity and strength of the cellular structure.The major matrix components are hemicellulose and pectin.
- hemicellulose is a polysaccharide, its structure similar to cellulose, but with shorter and branched chain monomers.
- Pectic substances also include polysaccharides, but their composition also includes residues of methyl alcohol.Due to the formation of chemical bonds with the ions of calcium and magnesium, pectin takes part in the formation of the middle of the plate - a place where two adjacent cells are interconnected.By the way, a large amount of pectin contained in the fruit of plants.
encrusted material in most cases represented the lignin, which is about 30% of the dry weight of the cell wall.
- Lignin can be deposited in the form of a continuous layer or in the form of separate elements - coils, meshes or rings.This material acts as a cement - it holds the cellulose fibers together.Thanks lignification, cell walls become more resistant and watertight Me.By the way, the lignin is responsible for the plant lignification.
Quite often, the outer surface of the cell membrane deposited substances such as cutin, wax and Suberin.
Suberin deposited on the inside of the cell membrane, ensuring the process suberization.Such a cell is absolutely impervious to moisture, so its contents are rapidly dying out, and the space is filled with air.
The main function of a waxy substance and the cuticle - is to protect cells from infection control, and reducing water evaporation.
can say that the cell wall - a very important element of the plant cell, which ensures its normal development.
