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| Experiments on Respiration |
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| Put some germinating seeds in a conical flask. With the help of a thread suspend a small tube containing KOH in the flask. Through the hole of the cork pass a glass tube bent twice at right angles. One end of the tube is in the flask while the other end is in the beaker filled with water. Make the apparatus air tight. Note the level of water in the tube. Keep the apparatus for sometime and note the position of water. |
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| It is observed that water rises in the tube. The rise in the level of water is due to a partial vacuum created in the flask because the gas produced during respiration is absorbed by KOH. This shows that germinating seeds produce CO2 during aerobic respiration as KOH can absorb CO2. |
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| This is aerobic respiration as KOH can absorb CO2 produced by seeds using air available. |
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| Experimental Setup for Aerobic Respiration |
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| Fill a test tube with mercury and invent it over a petridish containing mercury. Introduce some germinating seeds into the test tube. The seeds will immediately rise to top. Leave the set up for about a day. |
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| It is noted that the mercury level in the tube falls and the space above the mercury is filled with a gas. Insert some crystals of caustic potash into the top of the tube. The gas will be quickly absorbed by KOH and the level of mercury rises to the top. Since KOH absorbs carbon dioxide it is evident that the gas is CO2. |
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| Experimental Setup for Anaerobic Respiration |
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| The germinating seeds did not get O2, so they are exhibiting anaerobic respiration. |
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| Take a test tube and add about 10 ml of 10% glucose solution in it. Add a pinch of dry baker's yeast into the glucose solution and cover the surface of the liquid carefully with an oily layer to prevent the contact with air. Fix a holed cork into the mouth of the test tube and pass a delivery tube through it. The other end of the delivery tube is dipped in lime water. The whole apparatus is made air tight. The test tube with glucose is kept in warm water (37oC - 40oC) in a beaker. |
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| Experimental Setup to Show Alcoholic Fermentation in Yeast |
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| It is observed that after sometime, air bubbles arise and they turn the lime water milky showing that the air evolved is carbon dioxide. |
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| Open the cork of the test tube containing sugar and yeast. The smell of alcohol is observed. |
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| This shows that the products of anaerobic respiration by yeast are ethyl alcohol and carbon dioxide. |
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