Several kinds of bacteria can digest cellulose, breaking it down into its component elements. Cellulose-consuming animals, from termites to ruminants such as cattle, have populations of those bacteria living symbiotically in their stomachs.
Humans don't, so the cellulose in your foods has no nutritional value. You can chew it and swallow it, but it passes undigested through your intestines. That isn't necessarily a bad thing. The cellulose in plant-based foods is familiar to nutrition-label readers as dietary fiber, which plays an important role in human health.
In fact, it's precisely because cellulose is indigestible that it's important. As cellulose passes through the stomach and into the intestines, it provides much of the bulk that your digestive system uses for stool formation. The residue of your other foods is essentially "piggybacked" on the cellulose, making it possible for you to have regular bowel movements of predictable consistency.
There is a second type of dietary fiber, which -- although not digestible -- is at least soluble in water. When stored starch granules are removed from plants and placed in water they swell and release two types of material; amylose and amylopectin. Amylose is the simpler of the types of molecule and is largely linear chains of C1-to-C4 glysosides, several thousand units in length. Amylopectin is more complex and these molecules are branched using a combination of C1-to-C4 bonds and C1-to-C6 bonds about every 25 glucose units along the chain.
Such large, complex molecules do not dissolve well in water. Glycogen is also made by linking together glucose molecules. Like starch, it is used by animals to store sugar and provide energy. It is similar to amylopectin in structure, but branched with a C1-to-C6 glycosidic bond about every ten glucose units. Click here to. Components of Cells. Search for:.
Carbohydrates Learning Objectives Give examples of monosaccharides and polysaccharides Describe the function of monosaccharides and polysaccharides within a cell.
Think about It Why do monosaccharides form ring structures? Figure 3. Common disaccharides include maltose, lactose, and sucrose. Think about It What are the most biologically important polysaccharides and why are they important?
Key Concepts and Summary Carbohydrates , the most abundant biomolecules on earth, are widely used by organisms for structural and energy-storage purposes.
Carbohydrates include individual sugar molecules monosaccharides as well as two or more molecules chemically linked by glycosidic bonds. Monosaccharides are classified based on the number of carbons the molecule as trioses 3 C , tetroses 4 C , pentoses 5 C , and hexoses 6 C. They are the building blocks for the synthesis of polymers or complex carbohydrates.
Disaccharides such as sucrose, lactose, and maltose are molecules composed of two monosaccharides linked together by a glycosidic bond. Polysaccharides , or glycans , are polymers composed of hundreds of monosaccharide monomers linked together by glycosidic bonds.
The energy-storage polymers starch and glycogen are examples of polysaccharides and are all composed of branched chains of glucose molecules. The polysaccharide cellulose is a common structural component of the cell walls of organisms.
Other structural polysaccharides, such as N-acetyl glucosamine NAG and N-acetyl muramic acid NAM , incorporate modified glucose molecules and are used in the construction of peptidoglycan or chitin. Multiple Choice By definition, carbohydrates contain which elements?
Carbohydrates contain carbon, hydrogen, and oxygen. Show Answer Answer d. Monosaccharides may link together to form polysaccharides by forming glycosidic bonds. Matching Match each polysaccharide with its description. C Glycogen is an energy storage polymer found in animal cells and bacteria.
D Starch is a energy storage polymer in plants. A Cellulose is a structural polymer found in plants. Think about It What are monosaccharides, disaccharides, and polysaccharides? The figure depicts the structural formulas of glucose, galactose, and fructose.
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