Charlene Villanueva - Biology
Starch, Glycogen and Cellulose Independent Research
A polysaccharide is a long chain of monosaccharide molecules, held by glycosidic bonds. They are usually not sweet in taste, insoluble in water and often do not produce crystals when water is taken out.
Starch
Starch is a complex solid carbohydrate, consisting glucose molecules held together by glycosidic bonds. It is a storage polysaccharide. They can be found in fruits, seeds, roots and other parts of the plant.
The monomer of starch is glucose. Therefore, starch molecules can be made by polymerisation reaction, where glucose molecules are joined together to form a long chain. These starch molecules are held by glycosidic bonds.
Uses of starch * Forms parts of a cell wall * Energy storage * Can be digested by humans with amylase to make glucose for respiration * Plants use starch as stored energy for later use, breaking it down to glucose for respiration
Starch is a polysaccharide, so it has very large molecules. This means they are insoluble, so they are suitable for storage because they do not do osmosis, do not easily diffuse out of cells; is compact as a result of its glycosidic bonds’ angles giving it a coiled structure, making it possible for them to be stored in small places. It is also made up of small sub-units of alpha-glucose, making it easier for enzymes (amylase) to break down the molecule for an efficient release of glucose for respiration.
Glycogen
Glycogen is a highly branched polysaccharide which is the main form of storage in animals. It has a similar structure to starch, but glycogen has shorter chains. It is mostly stored in small granules in animals
Glycogen structure is similar to the structure of starch. Therefore, it is a large molecule, making it insoluble so it is suitable for storage in animals. It is also compact because of its glycosidic bonds giving it its coiled structure, so they can be
References: Anne Marie Helmenstine, Ph.D. (Unknown). Starch Definition. Available: http://chemistry.about.com/od/chemistryglossary/g/Starch-Definition.htm. Last accessed 25th Feb 2013. Wikipedia. (2002). Starch. Available: http://chemistry.about.com/od/chemistryglossary/g/Starch-Definition.htm. Last accessed 25th Feb 2013. Unknown. (Unknown). What are the different Polysaccharides?.Available: http://www.innovateus.net/science/what-are-different-polysaccharides. Last accessed 25th Feb 2013. Glenn & Susan Toole. (2008). Carbohydrates - disaccharides and polysaccharides; Starch, Glycogen and Cellulose. In: Nelson ThornesAQA AS Biology. Cheltenham: Nelson Thornes. 22, 156. J. France. (2005). Molecular difference between Alpha and Beta Glucose?. Available: http://www.thescienceforum.com/biology/15811-molecular-difference-between-alpha-beta-glucose.html. Last accessed 25th Feb 2013. Martin Chaplin. (2012). Cellulose. Available: http://www.lsbu.ac.uk/water/hycel.html. Last accessed 25th Feb 2013. Rene Fester Kratz, Donna Rae Siegfried. (2010). The Important Role of Cellulose to Plant and Animal Life. Available: http://www.dummies.com/how-to/content/the-important-role-of-cellulose-to-plant-and-anima.html. Last accessed 25th Feb 2013.