Filter the above mixture through muslin cloth, centrifuge the filtrate at low speed, take the supernatant liquid in a measuring flask and make up the volume of the enzyme extract upto 100 ml.ģ.
of germinating barley seeds and 20 ml of water and grind them in mortar.Ģ. KI in 300 ml water and use it as iodine solution.ġ. of monobasic sodium phosphate (0.2 M) in 250 ml of distilled water and use it as buffer solution A.ĭissolve 17.92 mg of dibasic sodium phosphate (Na 2HPO 4.12H 2O) in 250 ml of water to get 0.2 M buffer solution B. of soluble starch in 50 ml of boiling water.Īdd 6.95 gm. Germinating barley seeds, mortar, water, muslin cloth, centrifuge, measuring flask, iodine solution prepared in potassium iodide), starch solution, test tubes, beaker, enzyme extract, pipette, Benedict’s solution, buffer solutions of known pH, diastase solution, water baths (7), stop watch. The enzyme diastase acts on starch and converts it to hexose sugar. Experiment to study the enzyme activity of diastase in germinating seeds of barley and to study the influence of pH and temperature: Amylase is actually an enzyme which catalyzes the breakdown of starch into monosaccharide units. It is released during the crushing process. The enzyme amylase is present in the germinating barley or pea seeds. It is a reducing sugar, and a product of hydrolysis of starch made of amylase and amylopectin. Formation of reddish-brown colour after the addition of Fehling’s solution confirms the presence of hexose sugar. After about 30 minutes, the entire starch in tube ‘B’ gets completely hydrolysed into hexose sugar.ĭue to this the iodine solution gives negative test for starch. In tube ‘B’, formation of reddish-brown colour is due to the fact that addition of seed extract supplied the enzyme amylase which partially hydrolysed the starch into maltose (a 12-carbon sugar). However, if a few drops of Fehling’s solution are added in tube ‘B’, a brick-red precipitate appears.įormation of blue colour in tube ‘A’ confirms the test of starch. After about 15 minutes, if iodine solution is added, it shows no positive test for starch in tube ‘B’. In test tube ‘B’, the contents show reddish- brown colour. In test tube ‘A’, the contents turn blue in colour. Keep both the tubes at a warm place (about 35°- 40☌) for about 30 minutes. Add the filterate of the crushed cotyledons or endosperm of barely in tube ‘B’.Ħ. Add a few drops of iodine solution in tube ‘A’ and observe the colour change.ĥ.
Pour the starch solution in two test tubes and mark them as ‘A’ and ‘B’.Ĥ. Ground the cotyledons along with distilled water in the mortar, and filter the contents through a funnel.ģ. In case of pea seedlings, remove their cotyledons. Take a little amount of ordinary starch and make a thin paste of it in about 50 ml boiling water. Starch powder, iodine solution, germinating barley or pea seeds, distilled water, test tubes, mortar, pestle, filter paper, and funnel.ġ. (i) Test tubes must be thoroughly washed with water before use. Therefore, heat kills enzyme activity but has little effect on the activity of a catalyst. The enzymes are functional at room temperature (test tube three) but heating destroys their activity (test tube four). The catalyst is not affected by heat as it is clear from evolution of oxygen in the second test tube.įresh liver or potato contains enzymes peroxidase and catalase that help in evolving oxygen from hydrogen peroxide. Manganese dioxide is a catalyst that helps to break hydrogen peroxide into water and oxygen. Oxygen bubbles are found to come out of solution in the first three test tubes but not in the fourth one. Add a pinch of manganesedioxde in the first test tube, pre-boiled and cooled 1 ml of manganese dioxide solution in the second, small piece of fresh liver or potato in third and pre-boiled and cooled piece of liver or potato in the fourth.Īll the test tubes are kept at room temperature if it is summer and warm water (kept at about 38☌) if it is winter. Pour 2 ml of H 2O 2 solution is each of the four test tubes. Four test tubes, manganese dioxide (MnO 2), water, beaker, spirit lamp, piece of fresh liver or potato, hydrogen peroxide, boiled and cooled piece of liver or potato, boiled and cooled manganese dioxide solution.
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