Carbohydrates

Carbohydrates are the foundation of our food. For example, glucose, fructose, starch, and cellulose are formed continuously in plant and animal cells. They are the most important energy material for the body.

Carbohydrates are the foundation of our food

Carbohydrates possess common properties. This allows you to detect carbohydrates, even in very small quantities. Color reaction Molisch is a beautiful way of their recognition.

We perform the following experiment. Pour into a clean tube about 1 ml of water and add a few grains of sugar (sucrose), glucose tablets part or piece of filter paper. Now add 2-3 drops of an alcoholic solution of resorcinol or thymol. Tilt the tube and gently pour 1-2 ml of concentrated sulfuric acid. Make sure that the sulfuric acid does not hit the skin! Secure the vial in an upright position. Acid sink to the bottom. On the border acid with water will be bright beautiful ring. When a chemical reaction Molisch all carbohydrates produce similar ring.

Let us remember the lessons of biology in school, that is, turn to starch. Starch is one of the most famous of carbohydrates. Learn how to properly prepare a starch paste. Pour into the pan a little cold water and add two teaspoons of starch. The mixture was stir well. You will receive a so-called starch milk. While stirring, add the boiling water and heat up until the solution is clear. Cool it. This is the starch paste, which is very good glues paper.

In the next experiment, try to make glucose from starch paste. Glucose is a carbohydrate needed to man. She is one of the main suppliers of energy. But in bread, potatoes and pasta contains mainly starch. In the body it is converted into glucose by the enzymes. Under the influence of water large starch molecules split into smaller carbohydrates. First formed soluble starch. Then dextrins are formed, and maltose. In the decay of maltose, glucose is formed. The finished product contains all of the transitional substances. In this form it is known as molasses.

Everyone knows that in the presence of iodine starch turns blue. Prepare a tube with a weak solution of iodine. Up to half a cup of starch paste, add 1-2 teaspoons diluted 10% sulfuric acid. When diluted sulfuric acid is required to pour the acid into the water, and not vice versa!

Boil the paste with an acid, adding water when it evaporates. From time to time take a spoon of liquid samples. After cooling them slightly, drip on them with a dilute iodine solution. Starch is colored blue, the dextrin will be painted in a reddish-brown color. Carbohydrates maltose and glucose is not painted at all. During the experiment, the color samples will vary. When the iodine stain disappears, the heating can be stopped. For a more complete decomposition of maltose is necessary to boil the mixture for a few minutes.

After boiling, let cool a little liquid. Gradually add while stirring it about 10 g of chalk powder to completely neutralize the sulfuric acid. The mixture will foam, because during the reaction of the acid with chalk produces carbon dioxide. Once foaming ceased, heat the resulting liquid on low heat to evaporate it by about two thirds. Filter the hot mixture through several layers of cheesecloth. Then boil the liquid once again in a water bath. You will get a thick sweet syrup, which is based on glucose.

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