Cellulose << SEHL yuh lohs >> is a fibrous natural material that helps to strengthen plants and maintain their shape. Cellulose is also useful to people and other living things.
Cellulose is found within plant cells, where it is part of the cell wall. The cellulose makes the cells more rigid. Cellulose also is made by many kinds of algae, a group of aquatic animals called tunicates, and some bacteria.
Cellulose in fruits, vegetables, and whole grains provides essential dietary fiber. People cannot digest fiber, but it is important to healthy functioning of the intestines (see Fiber, Dietary). Industry uses plant matter rich in cellulose to manufacture such products as clothing, furniture, paper, and plastics. In addition, some cellulose in organisms that died millions of years ago became such fossil fuels as coal and oil.
Animals such as cattle and termites can digest cellulose with the help of microbes in the gut. Cellulose in dead plant material also provides food for bacteria, fungi, and other organisms. In fact, cellulose ranks as the most abundant biological material on Earth.
Structure.
Cellulose is a long chain of sugar molecules. Such a chain of molecules is known as a polymer. Many cellulose polymers crystallize (solidify together in an ordered way) into a cellulose fibril. The cablelike fibril has a tiny diameter but is quite long. Cellulose fibrils are often thousands of times as long as they are wide. For its small diameter, the fibril is exceptionally strong.
Plant cells make cellulose in the plasma membrane, immediately inside the cell wall. The sugar molecules used to build cellulose are made through photosynthesis. A specialized structure in the plasma membrane links together the sugar molecules into cellulose fibrils. The fibrils assemble with other carbohydrates and proteins to form the cell wall.
Industrial use.
People have used plant materials rich in cellulose to provide fuel, shelter, and clothing since prehistoric times. Commonly used materials include wood and cotton. Wood is about 40 to 55 percent cellulose. Cotton fibers are about 95 percent cellulose. Today, industry makes thousands of products using cellulose.
Cellulose is an essential component of many paper, packing, and hygiene products. Paper made from wood consists mostly of cellulose. Cotton fibers are spun into yarn for the manufacture of clothing and other textiles.
Manufacturers may use chemicals or other methods to release individual polymers from cellulose fibrils. These cellulose polymers can be processed into plastics such as cellophane and fabrics such as rayon. Other products made from cellulose include filters, glues, insulation, and thickeners.
Industry also can convert the cellulose in plant matter into fuels known as biofuels. These fuels can be used in place of such fossil fuels as gasoline. Biofuels from cellulose are attractive in part because cellulose is so abundant. Also, new plants can be grown, making such biofuel a renewable resource. In addition, biofuel can be made from the cellulose in agricultural waste or inedible plants. Some of these plants grow quickly on soil unsuitable for food crops. However, processing cellulose into biofuel has proven relatively costly. Scientists continue to develop improved technologies to make biofuel from cellulose at lower cost.
