Molecular Biology

What is Starch

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"What is Starch"
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Starch is an age-old substance that can be traced down the history line. Romans use it to augment their looks as a cosmetic; Egyptians being more technical used it as paste to stiffen weaved clothes and as adhesive; Chinese were literal about its use to improve paper quality, while Persians and Indians ate it as a dish.

Starch is a complex (polysaccharide) which is made up of smaller units called glucose, which are adhere together by glycosidic bonds. Its source is very natural, being produced by the relatively low organism, green plants. In pure form, it is a white, odourless and tasteless substance composed of two molecules: amylose and amylopectin. With amylopectin being the larger of the two by 80% to 20% in plants.

Plants use the process of photosynthesis to produce glucose by using sunlight and carbon dioxide. The glucose is then assembled together as semi-crystalline starch granules which are stored in the plants as food.

Its biosynthesis requires micro processes in green plants. The primary unit glucose-1-phosphate is converted to adenophosphate glucose with the use of ATP (Adenotriphosphate), this process is facilitated by the enzyme glucose-1-phosphate adenyltransferase.

ADP-glucose is then bonded (1, 4-alphaglycosidic bond) to a growing chain of other glucose residue; this second process is catalysed by the enzyme glucose syntase. ADP is released during this second process to produce amylase. 1, 6-alpha glycosidic bond is introduced into these chains to produce the branched amylopectin. Then isomylase, the starch debranching enzyme, remove some of these branches. After these processes the starch produced is stored in chloroplast and amyloplast of plants.

When animals eat starch in plants it is stored as glycogen; a branched form of amylopectin. The enzyme that breaks (hydrolysis) starch down is known as amylase. It can be found in saliva and pancrease. However other digestive enzymes find it difficult to digest starch.

Thus, in the small intestine it is digested poorly, while in the colon it is subjected to bacterial degradation. Starch is very important in nutrition of animals including humans. It constitutes the bulk of our foods, whether it is pasta, porridge, noodles, tapioca, potatoes or plain rice. Its calories are high and it provides sufficient energy for day-to-day workings of the body

Starch is soluble in water in high temperature turning into a gelatine-like substance (paste) by losing its semi-crystalline form. During prolong cooling it recovers its semi-crystalline form back, hence solidify. This explains it efficient usage as an adhesive.

As a food additive it serves as congealer, aiding the thickening of foods, such as custard, gravies, salad dressings and so on; also as a sugar for lots of foods and drinks. And in pharmacology it is used as bulk agents for lots of drugs, particularly capsules. Its commercial uses is a lot pronounced in paper making, where it is used to coat the paper to make it white as well as strengthens it. It s adhesive property cannot be overemphasised in industrial application.

As a glue it is used to for to hold together corrugated boards together to provide a lasting bond. In the laundry business, it is formulated into easy-to-use product that gives clothes a hardness that pronounces grace and style. Other industries it is used include: textile, printing, bioplastic, biofuel, oil exploration and hydrogen production.

More about this author: Damilola Owoyele

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