Cellulose
Cellulose, the major component of cell walls in plants, strengthens roots, leaves, and stems, making them rigid. It is a polysaccharide, a long molecule composed of oxygen, hydrogen, and sugar, and is very similar to the structures of sugars and starches. The hydroxide groups in cellulose are isotactic--that is, they are on alternating sides of the main chain. These pendant groups bind with others on long cellulose molecules to form microfibrils. French chemist Henri Braconnet (1780-1855), a leading figure in the field of animal and plant chemistry, verified the existence of cellulose in 1819, discovering the component in mushrooms and calling it fungine. He then began experimenting with the effects of sulfuric acid on wood. Braconnet eventually succeeded in creating a nitrated cellulose, which he called xyloidine, by adding wood or potato starch to nitric acid.
In 1834, Anselme Payen, another French chemist, succeeded in isolating cellulose from wood. He named it cellulose because it is found in the cell walls of most plants. In 1838, Theophile-Jules Pelouze (1807-1867), a French chemist, also developed nitrocellulose--just one achievement in his long and significant career in chemistry. His career began as a lab assistant and student of Joseph Gay-Lussac. He became a professor at Lille in 1830 and then moved on to teach at Ecole Polytechnique, conducting many successful experiments with Gay-Lussac and on his own. Pelouze eventually established a private laboratory school for chemistry in Paris, where he trained students and allowed foreign chemists to conduct private research. He died in Paris in 1867.
Not until the late 1930s did we know how cellulose is formed. Wanda Farr, an American scientist, solved the mystery. Until Farr's research, scientists only knew that small cellulose granules would appear in the protoplasm of plant cells. Farr graduated from Ohio University with a doctorate in science and went on to study botany and mathematics. She studied at the Barnard Skin and Cancer Clinic and learned how to grow living cells in a petri dish.
While studying a single-cell plant from Bermuda, Farr saw a green plastid manufacture a substance later analyzed as cellulose. She theorized that plastids were responsible for cellulose production in other plants but were unseen because their refractive index was so close to that of the mounting fluid. When the cells were remounted, the plastids were easily visible under a microscope.
Today cellulose is part of a number of common products. Rayon and cellophane are made by treating cellulose with an alkali and then exposing it to fumes of carbon disulfide, which yields threads and films. Cellulose acetates are used in photographic safety film and certain fabrics, and as a substitute for glass and a molding material. Cellulose ethers are used in paper sizings, adhesives, soaps, and synthetic resins. When mixed with nitric and sulfuric acids, cellulose forms flammable and explosive compounds, known as cellulose nitrates. Such nitrates include pyroxylin, found in various lacquers and plastics; collodion, used in medicine, photography, and artificial leather manufacture; and guncotton, an explosive.
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