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Plant cell walls have two main functions: to provide rigidity for the cell, and to prevent expansion when water enters the cell. The term turgor is used to describe this pressure that is induced by excess water inside the plant cell.
The cell wall is generally permeable to anything entering the cell in solution unless impregnated with lignin in wood or suberin in cork tissue to produce wood.
The primary cell wall, built by the plant first, is composed of cellulose microfibril s aligned at all angles. Microfibrils are held together by hydrogen bonds to provide a high tensile strength. After the maximum size necessary has been reached, a secondary wall is constructed below. Unlike the primary wall, the microfibrils are aligned mostly in the same direction, and with each additional layer the orientation changes slightly.
Cell walls of neighbouring cells are held together by a shared gelatinous membrane called the middle lamella, which contains magnesium and calcium pectate s (salts of pectic acidPectic acid is a transparent and gelatinous acid existing in ripe fruit and some forms of vegetable. It has a chemical composition of CHO.).
Made of insoluble cellulose fibres meshed in to a matrix of carbohydratesCarbohydrates (literally hydrates of carbon are chemical compounds that act as the primary biological means of storing or consuming energy, other forms being fat and protein. Relatively complex carbohydrates are known as polysaccharides. Carbohydrates are called pectates and hemicelluloses, they give the plant strength and support.
Cell walls of bacteria are primarily used for protection against hostile environments or, in the case of pathogenA pathogen is a biological agent that can cause disease to its host. A synonym of pathogen is " infectious agent". The term "pathogen" is most often used for agents that disrupt the normal physiology of a multicellular animal or plant. However, pathogensic bacteria, against the immune systemThe immune system is any system present in an organism to prevent predation by biological agents. All living organisms have these protective measures, although they vary radically in scope and mechanism. In humans and domesticated animals, the immune syst of the hostIn biology, a host is an organism that harbors a parasite, mutual partner, or commensal partner, typically providing nourishment and shelter. See symbiosis. Examples: A cell can be host to a virus, a legume plant can be host to helpful nitrogen-fixing bac. They contain peptidoglycanPeptidoglycan also known as murein, is a homogenous layer lying outside the plasma membrane in prokaryotes. The peptidoglycan layer is thicker in Gram-positive bacteria (20 to 80 nm) than in Gram-negative bacteria (7 to 8 nm). It forms around 90% and 10%, which can be made visible in Gram-positiveGram-positive bacteria are those that are stained dark blue or violet by gram staining, in contrast to gram-negative bacteria, which are not effected by the stain. The stain is caused by a high amount of peptidoglycan in the cell wall, which typically lac bacteria by Gram stainingGram staining is a method for staining samples of bacteria that differentiates between the two main types of bacterial cell wall. It is named after the inventor, the Danish scientist Hans Christian Gram (1853-1928), who developed the technique in 1884 to. The cell walls of bacteria are also vital for containing the high osmotic pressure inside bacterial cells caused by the high concentration of solutes in the cytoplasm, which can often be as high as 15 atmospheres. Many antibiotics, including penicillin and its derivatives, target the cell wall of bacteria.