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2.3

Major VersionM

by Raghottam Joshi

Introduction

Yeast can respire - even in the absence of oxygen - breaking down sugar, releasing carbon dioxide and other by products.

Yeast is allowed to act on sugar water in a bottle, the mouth of which is sealed with a balloon. Over time, as the yeast starts to digest the sugar, the balloon starts to inflate!

This process is called anaerobic respiration and is used to make beer and wine.

Video Overview

    • Do not inhale/ingest yeast. It is a fungus!

    • Wash your hands thoroughly after handling yeast.

  1. Measure approximately 150 ml of water and pour it into a cut bottle or any available container. You can use: 17 ml glass test tube( 8 full glass test tubes)
    • Measure approximately 150 ml of water and pour it into a cut bottle or any available container. You can use:

    • 17 ml glass test tube( 8 full glass test tubes)

    • 6 ml plastic test tube (25 full plastic test tubes).

    • 3 ml droppers (50 full plastic droppers) or any other liquid measure available to you.

    • Transfer the measured 150 ml of water into a bottle.

  2. Measure 7 cm from one end of a straw and make a line with a sketch pen. Pinch the straw end (from where you measured) and tape it as shown in the picture [The pinching is done to avoid the powder sticking to the tape]. Cut the straw at the marked line. This straw piece measures 3 g of sugar.
    • Measure 7 cm from one end of a straw and make a line with a sketch pen.

    • Pinch the straw end (from where you measured) and tape it as shown in the picture [The pinching is done to avoid the powder sticking to the tape].

    • Cut the straw at the marked line. This straw piece measures 3 g of sugar.

  3. Fill the sugar completely, till the brim of measurement cup . One full unit contains  3 g of sugar. One full unit contains  3 g of sugar.
    • Fill the sugar completely, till the brim of measurement cup .

    • One full unit contains 3 g of sugar.

  4. Pour the sugar into the bottle and dissolve completely by gently shaking it. Pour the sugar into the bottle and dissolve completely by gently shaking it. Pour the sugar into the bottle and dissolve completely by gently shaking it.
    • Pour the sugar into the bottle and dissolve completely by gently shaking it.

  5. Fill the measuring cup till the brim with yeast; this is equal to about 2 g of yeast. Pour the yeast into the bottle, which contains the sugar solution. Shake the bottle well to mix the contents.
    • Fill the measuring cup till the brim with yeast; this is equal to about 2 g of yeast.

    • Pour the yeast into the bottle, which contains the sugar solution.

    • Shake the bottle well to mix the contents.

  6. Stretch the balloon and fix it over the mouth of the plastic bottle. Stretch the balloon and fix it over the mouth of the plastic bottle. Stretch the balloon and fix it over the mouth of the plastic bottle.
    • Stretch the balloon and fix it over the mouth of the plastic bottle.

  7. Secure the balloon to the bottle with rubber bands. Secure the balloon to the bottle with rubber bands. Secure the balloon to the bottle with rubber bands.
    • Secure the balloon to the bottle with rubber bands.

  8. Use insulation tape to further secure the balloon to the bottle to avoid any chance of gas leakage. Use insulation tape to further secure the balloon to the bottle to avoid any chance of gas leakage. Use insulation tape to further secure the balloon to the bottle to avoid any chance of gas leakage.
    • Use insulation tape to further secure the balloon to the bottle to avoid any chance of gas leakage.

  9. Shake the bottle for a few seconds, once in every half an hour. After one hour of incubation After two  hours of incubation
    • Shake the bottle for a few seconds, once in every half an hour.

    • After one hour of incubation

    • After two hours of incubation

    • After three hours of incubation

  10. You should observe the balloon inflate gradually, perhaps visibly so after about 3 hours of incubation.
    • You should observe the balloon inflate gradually, perhaps visibly so after about 3 hours of incubation.

  11. Once the reaction stops, say after a couple of hours, stretch the balloon slightly at the neck and twist it around 4-5 times. A neck area will form that you can secure with a thread. Tie the balloon using a cotton thread at the neck (twisted part) to prevent the gas from escaping the balloon. You may need the help of a friend to do this. Holding the free end of the cotton thread, remove the rubber bands, tape and balloon from the mouth of the bottle.
    • Once the reaction stops, say after a couple of hours, stretch the balloon slightly at the neck and twist it around 4-5 times. A neck area will form that you can secure with a thread.

    • Tie the balloon using a cotton thread at the neck (twisted part) to prevent the gas from escaping the balloon. You may need the help of a friend to do this.

    • Holding the free end of the cotton thread, remove the rubber bands, tape and balloon from the mouth of the bottle.

  12. Note the initial water level. Immerse the inflated balloon completely, as shown in the in picture. Note the final water level.
    • Note the initial water level.

    • Immerse the inflated balloon completely, as shown in the in picture.

    • Note the final water level.

    • Note down the increase in volume. This is nothing but the volume of the balloon.

    • You may also fill an un-graduated bucket with water to the brim. Place it in a tub. Immerse the balloon and allow the overflow to collect in the tub. And then measure the volume of the displaced water with a measuring jar.

  13. Make the filter paper cone as shown, following labelled Steps from 1-4. Put the above made filter paper in the bottle cut-out apparatus, using the bottom part as a filtering stand. Take about one and a half units of lime (CaO) powder, which is about 1-2 g. Add about 30 ml of water and mix thoroughly. Filter the solution using the filter paper setup, to get filtered lime water - Ca(OH)2.
    • Make the filter paper cone as shown, following labelled Steps from 1-4.

    • Put the above made filter paper in the bottle cut-out apparatus, using the bottom part as a filtering stand.

    • Take about one and a half units of lime (CaO) powder, which is about 1-2 g. Add about 30 ml of water and mix thoroughly. Filter the solution using the filter paper setup, to get filtered lime water - Ca(OH)2.

    • Make sure the filtrate is clear. If not, filter it again.

  14. Take about 4 ml of the prepared lime-water in a test tube, and attach the balloon to its mouth and after removing the string. Squeeze the balloon while holding it tight to enable the gas to enter the test tube quickly. Notice that as the gas from the balloon dissolves into the lime water, it should turn milky.
    • Take about 4 ml of the prepared lime-water in a test tube, and attach the balloon to its mouth and after removing the string.

    • Squeeze the balloon while holding it tight to enable the gas to enter the test tube quickly.

    • Notice that as the gas from the balloon dissolves into the lime water, it should turn milky.

    • You may shake the test tube vigorously to speed up the reaction.

    • No inflation in balloon -

    • Check for the complete dissolution of sugar.

    • Check the amount of sugar or yeast is adequate.

    • Check for the leakage in the balloon.

    • Allow sufficient time for the reaction to occur.

    • Lime water doesn't turn milky - Gas has escaped out,

  15. Try anaerobic respiration using a different food item (wheat flour) instead of sugar. Keep the amount of yeast constant and vary the substrate (sugar).  Try using glucose and jaggery. Try anaerobic respiration using lukeworm water and ice cold water.
    • Try anaerobic respiration using a different food item (wheat flour) instead of sugar.

    • Keep the amount of yeast constant and vary the substrate (sugar). Try using glucose and jaggery.

    • Try anaerobic respiration using lukeworm water and ice cold water.

    • For more variations, Go to Respiration - Anaerobic (Variations).

Finish Line

Madhushree HS

Member since: 05/02/2017

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