Cellulose why cant humans digest

The digestion of cellulose occurs in a four-chambered stomach. Cellulose is the most abundant organic polymer founded on the earth which occurs naturally. Introduction to what is Cellulose. Cellulose is a complex polymeric carbohydrate molecule that comprises thousands of glycosidic linkages in the form of a linear chain.

The chain is unbranched and straight consisting of linked D-Glucopyranose bonded by hydrogen bonds producing a substance which in its pure form is insoluble and inert. Structure of Cellulose. A large number of organisms ranging from the bacterium Acetobacter xylinum synthesizes cellulose from the forest trees. A good amount of cellulose is produced by A.

Xylinum and also this bacteria is used in the study of cellulose biosynthesis. The protein named enzyme cellulose synthase present in the membrane synthesizes cellulose as well as catalyzes the glucose polymerization from UDP- glucose into the product of cellulose.

There are many bacteria, Dictyostelium disodium, and higher plants from which genes for cellulose synthesis can be identified. From the Cellulose which is present in plants to the bacterial cellulose, all are arranged in a similar way from the microfibrils as chains of polysaccharide and from ribbon bundles of microfibrils.

In the human body, cellulose cannot be digested due to a lack of appropriate enzymes to break the beta acetal linkages. The human body does not have the digestive mechanism to break the monosaccharide bonds of cellulose.

Although cellulose is indigestible then also it helps in the smooth working of the intestinal tract. But, it plays a vital and necessary role in the human body because it is an excellent source of fiber. Every kind of sugar can be digested by the enzymes secreted from the human mouth, liver, and stomach except cellulose.

There are some foods like fermented food, grains, and vegetables which are hard to digest or are indigestible. By means of the symbiotic gut bacteria, cellulose can be digested by herbivores with the help of monogastric digestion. Herbivores are less efficient than ruminants in the case of extracting energy from the digestion of cellulose. Here, cellulose is digested by microbial fermentation.

Herbivores eat plant materials as their food and the cell walls in plants contain cellulose. Polysaccharides are carbohydrate polymers consisting of tens to hundreds to several thousand monosaccharide units. All of the common polysaccharides contain glucose as the monosaccharide unit. Polysaccharides are synthesized by plants, animals, and humans to be stored for food, structural support, or metabolized for energy.

The major component in the rigid cell walls in plants is cellulose. Cellulose is a linear polysaccharide polymer with many glucose monosaccharide units. The acetal linkage is beta which makes it different from starch.

This peculiar difference in acetal linkages results in a major difference in digestibility in humans. Humans are unable to digest cellulose because the appropriate enzymes to breakdown the beta acetal linkages are lacking. More on enzyme digestion in a later chapter. Undigestible cellulose is the fiber which aids in the smooth working of the intestinal tract. Animals such as cows, horses, sheep, goats, and termites have symbiotic bacteria in the intestinal tract.

These symbiotic bacteria possess the necessary enzymes to digest cellulose in the GI tract. They have the required enzymes for the breakdown or hydrolysis of the cellulose; the animals do not, not even termites, have the correct enzymes.

No vertebrate can digest cellulose directly. Even though we cannot digest cellulose, we find many uses for it including: Wood for building; paper products; cotton, linen, and rayon for clothes; nitrocellulose for explosives; cellulose acetate for films. The structure of cellulose consists of long polymer chains of glucose units connected by a beta acetal linkage. The graphic on the left shows a very small portion of a cellulose chain. All of the monomer units are beta-D-glucose, and all the beta acetal links connect C 1 of one glucose to C 4 of the next glucose.

Cellulose - Chime in new window. Carbon 1 is called the anomeric carbon and is the center of an acetal functional group. A carbon that has two ether oxygens attached is an acetal. The Beta position is defined as the ether oxygen being on the same side of the ring as the C 6. In the chair structure this results in a horizontal or up projection. This is the same definition as the -OH in a hemiacetal. Open graphic of hemiacetal in a new window Compare Cellulose and Starch Structures:.

Cellulose: Beta glucose is the monomer unit in cellulose.