cellulose, chief constituent of the cell walls of plants. Chemically, it is a carbohydrate that is a high molecular weight polysaccharide. Raw cotton is composed of 91% pure cellulose; other important natural sources are flax, hemp, jute, straw, and wood. Cellulose has been used for the manufacture of paper since the 2d cent. Insoluble in water and other ordinary solvents, it exhibits marked properties of absorption. Because cellulose contains a large number of hydroxyl groups, it reacts with acids to form esters and with alcohols to form ethers. Cellulose derivatives include guncotton, fully nitrated cellulose, used for explosives; celluloid (the first plastic), the product of cellulose nitrates treated with camphor; collodion, a thickening agent; and cellulose acetate, used for plastics, lacquers, and fibers such as rayon.

C₂H₃O₂⁻ ion, a salt, ester, or acylal derived from acetic acid. Acetates are important in the biochemical synthesis of fats from carbohydrates in plants and animals. Industrially, metal acetates are used in printing, vinyl acetate in plastic production, cellulose acetate in photographic films and textiles (one of the first synthetic fibres, often called simply acetate), and volatile organic esters as solvents.

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Complex carbohydrate (polysaccharide) consisting of 1,000–3,000 or more glucose units in a linear chain structure that can pack into fibres of great tensile strength. The basic structural component of plant cell walls, cellulose is the most abundant of all naturally occurring organic compounds (90percnt of cotton and 50percnt of wood). Mammals (including humans) cannot digest cellulose, but bacteria in the rumens of cattle and other ruminants and protozoans in the gut of termites produce enzymes that can break it down. Soil fungi can also break down cellulose. Its most important uses are in wood, paper, and fibre products, as an ethanol and methanol source, and specialized applications. Cellulose derivatives are used in plastics, photographic films, rayon fibres, cellophane, coatings, explosives (e.g., nitrocellulose), and foods (e.g., the stabilizer and thickener carboxymethylcellulose).

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