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CLASS- X EPISODE-2 STATE SYLLABUS

RESPIRATION    Factors

The process of respiration is dependent on a number of factors.Understanding the factors that control the process of respiration goes a long way in preservation of fruits, vegetable and food items. It is also useful in treatment of diseases and in control of pests.

What are the factors that control respiration? the factors that control respiration are……

1) Oxygen 2) Temperature

We have learnt in the study on photosynthesis how oxygen is important. If oxygen is not present NADH and FADH2 are not oxidized and ATP, most essential for energy,is not produced.

Very few organisms like yeast and bacteria can live in the absence of oxygen. Yeasts derive energy by glycolysis and by fermenting the sugars to alcohol. Bacteria produce lactic acid in the absence of oxygen.Other than these few micro organisms, animals and plants cannot survive without oxygen. Rate of respiration increases to obtain more oxygen and expel carbon dioxide in an atmosphere of low oxygen.

To understand how respiration can occur both in aerobic (presence of oxygen) and anaerobric(absence of oxygen) conditions can be demonstrated by an experiment.

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Animate- story board1). Take two bottles with cork to close the mouth.3). Put a small beaker with lime water in each beaker.4). Put dry seeds in one bottle and germinating seeds in another bottle.5). Close the mouth and apply grease or Vaseline to prevent air going out of the bottle.6). Keep the bottles undisturbed for two days.7). After two days in the bottle with germinating seeds there is greater amount of precipitate.8). It demonstrates that CO2 is released during respiration by germinating seeds.Another experiment to demonstrate anaerobic respiration we will use the same bottles. Instead of seeds add 150 to 200ml of glucose solution and baker yeast. The glucose solution is now covered with oil to prevent the solution from contact with air. After one or two days when we remove the cork the smell of alcohol is sensed. This proves that respiration does take place in the absence of oxygen or anaerobic conditions.

What is the second factor?The second factor controlling respiration is temperature. As the temperature increases there is an increase in the rate of respiration. You could have felt the same thing in summer. You can observe it very clearly in dogs. The rate of respiration doubles for every 100C increase in temperature. However beyond 450C the rate of respiration decreases.

The temperature at which the rate of respiration is high is called as OPTIMUM TEMPERATURE.

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At low temperatures enzymes are not active. The rate of respiration reduces. This knowledge has been utilized by man to devise technology to preserve food, fruits, vegetables etc. at low temperatures. Frozen food will not spoil for a long time.At high temperatures enzymes are denatured or killed and become inactive.

How is energy liberated?Oxidation of food involves the liberation of some amount of energy in the form of heat. This can be demonstrated by an experiment.Animate

1. Take some seeds in a beaker.2. Soak them in water for a day.3. Place these seeds in a thermos flask and close the mouth of flask with

cork. The cork should have a hole in the center.4. Take another bottle and put dry seeds in it and close it like the other

bottle.5. introduce a thermometer into each flask through the hole in the cork.6. Seal the hole with grease or Vaseline.7. Note the temperature every hour for 24 hours.

8.In the first bottle the temperature rises very little while in the second bottle show the rise of temperature as the seeds germinate.

You will observe that the temperature in the bottle having soaked seeds and which have started germinating increases and is higher than the bottle containing dry seeds. This proves that heat is generated during respiration.

Having understood the factors controlling respiration let us now study the organs of respiration in different animals.

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