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Karen Chung

on 22 April 2013

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Transcript of Starch

Starch Why the need for this material? Starch is used as a chief form of storage for excess glucose sugars by most plants. Glucose is made as a product of photosynthesis in plants and is converted to starch though a process known as polymerisation. This is important as plants may not use all the glucose it produces immediately, therefore, plants store it in the form of starch and can be broken down for future usage. What bonding (intra/inter) exists in the material? Starch is a polysaccharide that is made of many monosaccharides held together by glycosidic (covalent) bonds. The glycosidic bonds join carbon 1 of one glucose molecule to carbon 4 of another glucose molecule and forms one long chain of glucose molecules. When the glucose molecules are bonded together, a water molecule is released as part of the synthesis of two glucose molecules. This is known as a condensation reaction. What is the overall structure starch? Starch can be broken down into two different molecules, amylose and amylopectin. Glucose molecules are linked linearly in amylose but has an overall spiral structure. How does the bonding influence the chemical and physical properties? Starch is generally insoluble in water or alcohol due to the intramolecular hydrogen bonding in its structure but becomes soluble when heated as the granules swell and burst, destroying the semi-crystalline structure. The amylose molecules contained in starch is released by the granule and forms a network that holds water. This also increases the viscosity of the solution. When cooked, starch increases viscosity. This is known as starch gelatinisation. Gelatinisation breaks down the intermolecular forces of starch. When cooled or prolonged storage of starch, the semi-crystalline structure partially recovers, and water is released, thickening the solution. The insolubility of starch also makes it good for storage as it does not interrupt the osmotic balance in the plant.

The molecule is also very simple, allowing it to be broken down easily by enzymes. The linear arrangement of amylose and the branched strcuture of amylopectin enables molecules to be compact and good for storage. Starch molecules can also be easily converted to glucose when necessary due to the structure of starch.

Starch has a autoignition temperature of 410 degrees Celsius and a density of 1.5g/cm^3. What are the raw materials? Starch is primarily made up of many glucose monosaccharides joined together by glycosidic bonds. A glucose (C6H12O6) molecule consists of Carbon, Hydrogen and Oxygen at a ratio of 1:2:1.

Glucose is stored in plants as starch. Glucose is made naturally by plants through photosynthesis by converting light energy to chemical energy and is then converted into starch through polymerisation. What is the environmental impact of biopolymers? Biopolymers are polymers produced by living things, therefore have little negative environmental impact on the environment. Biopolymers can be sustainable, carbon neutral and are always renewable. It is sustainable because it is extracted from plant materials that come from agricultural non-food crops; it is carbon neutral because as it decomposes, it releases carbon dioxide but is reabsorbed by crop grown, therefore they are carbon neutral. Biopolymers are also biodegradable because they can be broken down into carbon dioxide and water by microorganisms.

Starch itself is environmentally friendly and has little or no environmental impact as it is naturally produced by plants. However, the production of sugars do have have negative impacts on our environment. Sugar production can affect our biodiversity as many forest areas have been cleared for sugar production, which leads to the destruction of natural habitats and may result in the extinction of endangered species who live in these areas. Increased air pollution and soil degradation have also occurred as a result of sugar cultivation from excess production of plants in an concentrated area and from burning "cane trash" (cane stalks and leaves). Starch or glucose (sugar) is generally carbon neutral but the high demand for sugar production has resulted in a negative impact for our environment. Bibliography Kinnear, Judith and Martin, Marjory, Nature of Biology Book 2 (4E), Jacaranda, Page 13-14 on 5/04/13

Biodegradable Polymers (Biopolymers) (2007) Retrieved on 10/04/13 from:http://www.biodeg.net/biopolymer.html

Chaplin, Martin, Starch (2012) Retrieved on 5/04/13 from:http://www.lsbu.ac.uk/water/hysta.html

Encyclopaedia Britannica, Starch (2013) Retrieved on 18/04/13 from:http://www.britannica.com/EBchecked/topic/563582/starch

Fisher, Matthew A., Starch (2013) Retrieved on 5/04/13 from:http://www.chemistryexplained.com/St-Te/Starch.html

Ophardt, Charles E., Starch (2003) Retrieved on 7/04/13 from:http://www.elmhurst.edu/~chm/vchembook/547starch.html

Wikipedia, Starch (2013) Retrieved on 6/04/13 from: http://en.wikipedia.org/wiki/Starch

Amylose Structure Amylopectin Structure What is starch? Starch is a complex carbohydrate (sugar), made up of glucose monomers, found in plants as a form of storage for excess glucose. It is used in cooking, industry (paper, adhesives, textiles) and other means. Starch is commonly found in foods such as potatoes, corn, wheat and rice. The basic chemical formula for starch is (C6H10O5)n.

Starch usually appears as a white, odourless and tasteless powder. For Amylopectin, glucose molecules are linked in a linear arrangement and have different linkages between two adjacent glucoses, forming branches in the structure. There is generally more amylopectin than amylose in plant starch at a ratio of 20:80 or 30:70. Starch has a semi-crystalline structure. Each glucose molecule has a hexagonal ring structure containing six carbon atoms. Starch is made up of long chains of glucose molecules connected by glycosidic bonds between carbon 1 of a glucose molecules and carbon 4 of the next glucose molecule. Starch also has intramolecular hydrogen bonds. These bonds are mostly found between hydrogen and oxygen atoms of starch molecules. Part of a starch molecule. Starch, as carbohydrates, make up a large portion of our diet as it is found in nearly all foods we consume, such as vegetables and fruits. When we consume these plants that store glucose as starch, the starch within these plants will be broken down into glucose as our body digests it by two enzymes amalayse and maltase. Amylase hydrolyses (breaks down) starch into maltose (disaccharide) and maltase hydrolyses maltose into two glucose molecules (monosaccharide). Glucose then becomes a source of energy for our cells to undergo biochemical processes such as cellular respiration in the mitochondrion of our cells.

Starch is also used for cooking and paper making to increase the strength of the paper. By Karen Chung Starch vs. Glucose Differences between Cellulose, Starch and Glycogen Cellulose, starch and glycogen are all complex carbohydrates and are formed by multiple glucose molecules bonded together. The main differences between these three materials is that cellulose is a structural polysaccharide in plants, starch is a storage polysaccharide in plants and glycogen is a storage polysaccharide in animals. There are also different types of bondings within each polysaccharide. Environmental Impacts of Sugar Production (2013) Retrieved on 10/04/13 from:http://www.sugarcoconut.com/blogs/21-environmental-effects
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