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Enzymes accelerate for many chemical reactions, h o do it selectively. Each of them has its own narrow specialty, the same process is accelerated sometimes several enzymes. We now verify.

Consider destroying enzymes starch attach to his "pieces" of water molecules, i.e. hydrolytic enzymes. Among them - amylase, which we have already talked on the page "Experiments with carbohydrates". Because the essence of the action of such enzymes you already know, will immediately comparative experiments: let's see how to act on the starch amylase humans and animals.

Source of amylase person will serve as saliva. Amylase animal you will find in the honey bee.

Cook first five solutions. First solution: collect in a test tube 0.5 ml of saliva and dilute with cold boiled water twenty times. Second solution: very liquid starch paste (a quarter teaspoon of cornstarch per Cup of water). Third solution: diluted with water twenty times pharmacy iodine tincture. Fourth solution: two-three drops of honey, diluted with water ten times and thoroughly mixed. The fifth solution: half a teaspoon of baking soda in ten spoons of water

You will need nine tubes. In all test tubes pour about 5 ml of paste. In tubes 1, 4 and 7 add by pipette 5 drops of vinegar, and in tubes 2, 5 and 8 - the same amount of soda solution. In the other test tube add 5 drops of pure water. The contents of all tubes, mix and each dispense 10 drops of diluted saliva.

After 10 min in test tubes 1, 2 and 3 add one or two drops of a solution of iodine and stir the mixture. Observe the colour change. Even after 15 minutes add the same dose of iodine in tubes 4, 5 and 6, and another 10 min in the remaining tubes. Starch and dextrins, as you remember, give a different color from the hearth, and as the destruction of starch by amylase color changes. So it is possible to judge not only the disintegration of the starch, but also about what the environment is acidic, neutral or alkaline - more favorable for this process.

Experience with bee honey is just the same. The activity of amylases in different samples can vary greatly, so perhaps the time of hydrolysis is necessary to decrease or increase. For example, in the saliva of smokers amylase contains very little.

For the next experiment will need barley malt is germinated barley grain. Soak the grain in water for a few hours and leave them to sprout and saucer for 4-5 days, each day adding a little water. The seedling remove, rinse with water and carefully RUB a wooden pestle or spoon. The dilute slurry of double distilled water and squeeze through tight cloth into a glass. This extract contains two enzymes: alpha-amylase and beta-amylase. Additional processing can destroy one of them to observe the action of another. Alpha-amylase will destroy the heat. To one part of the extract from barley, add three parts water, stir the mixture and heat it for 20 min in a water bath at 70°C, mixing thoroughly. The cooled solution contains beta-amylase.

Now, to obtain a solution of alpha-amylase, it is necessary to destroy the beta-amylase acid. About 5 ml of the extract to cool up to 2-3°C in the refrigerator or on ice, add incomplete teaspoon of the cooled vinegar and fill the tube almost to the top with cold water. The mixture stir and leave for 15-20 min, and then neutralize the solution by adding powder of chalk to stop shedding vesicles. Again stir the mixture, dilute twice with water, let it settle and pour off the liquid above the sediment into a clean tube. This training experience is over.

Ten tube pour 1 ml of starch solution and 9 ml of water. In test tubes 1-5, add by pipette ten drops of a solution of alpha-amylase, in the other tubes, the same solution of beta-amylase. The contents of all tubes, mix well. After 3 min in tubes 1 and 6 add one drop of a solution of iodine and stir. Do the same with the tubes 2 and 7 after 5 min, 3 and 8 through 10 min, 4 and 9 through 20 min, 5 and 10-30 minutes

You will notice that in the presence of alpha-amylase colour changing rapidly: blue-purple - pink-yellow: the formation of dextrins - fragments of molecules of starch. Beta-amylase is another: it is as if "bites off" pieces from the starch molecules, and therefore the coloration with iodine remains blue, but in the process of disintegration of starch, its brightness decreases.

The results of this experience clearly show a variety of properties even at similar enzymes. In living organisms, the enzymes usually act together. What if this transformation is much more than those relatively simple reactions that you observed in test tubes. But the simple knowledge is the first step to knowledge difficult.

O. Holguín. "Experiments without explosions"
M., "Chemistry", 1986


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