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In addition, cellulose is a straight chain polymer, and each cellulose molecule is long and rod-like. This differs from starch, which is a coiled molecule. A result of these differences in structure is that, compared to starch and other carbohydrates, cellulose cannot be broken down into its glucose subunits by any enzymes produced by animals.
The structural components of plants are formed primarily from cellulose. Wood is largely cellulose and lignin, while paper and cotton are nearly pure cellulose. Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many animals lack an enzyme to break the beta-linkages, so they do not digest cellulose.
Cellulose is an organic compound with the formula (C 6 H 10 O 5) n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. [3] [4] Cellulose is an important structural component of the primary cell wall of green plants, many forms of algae and the oomycetes.
Starch: Starch is an inexpensive biodegradable biopolymer and copious in supply. Nanofibers and microfibers can be added to the polymer matrix to increase the mechanical properties of starch improving elasticity and strength. Without the fibers, starch has poor mechanical properties due to its sensitivity to moisture.
Starch has been classified as rapidly digestible starch, slowly digestible starch and resistant starch, depending upon its digestion profile. [45] Raw starch granules resist digestion by human enzymes and do not break down into glucose in the small intestine - they reach the large intestine instead and function as prebiotic dietary fiber. [46]
Based on the structural difference, like backbone linkages and side groups, as well as other factors, like abundance and distributions in plants, hemicelluloses can be categorized into four groups as following: [4] 1) xylans, 2) mannans; 3) mixed linkage β-glucans; 4) xyloglucans.
Two common examples are cellulose, a main component of the cell wall in plants, and starch, a name derived from the Anglo-Saxon stercan, meaning to stiffen. [2] To name a polysaccharide composed of a single type of monosaccharide, that is a homopolysaccharide, the ending “-ose” of the monosaccharide is replaced with “-an”. [3]
Dietary fiber is defined to be plant components that are not broken down by human digestive enzymes. [1] In the late 20th century, only lignin and some polysaccharides were known to satisfy this definition, but in the early 21st century, resistant starch and oligosaccharides were included as dietary fiber components.