ANAEROBIC RESPIRATION

The respiration which takes place in the absence of oxygen is called anaerobic respiration. Ex; yeast and some kinds of bacteria. 
The end products of anaerobic respiration are : lactic acid and carbondioxide (with very little amount of heat ) in bacteria and 
Ethyl alcohol and carbondioxide (with little amount of heat) in yeast. 
When we make dough by adding yeast for making buns, pizza bases, bread etc we observe a peculiar smell of ethyl alcohol. Here yeast undergoes anaerobic respiration reacting with sugar in white flour and releasing carbondioxide gas which gets trapped in the dough due to which holes are formed in the dough. 
DEMOSTRATING ANAEROBIC RESPIRATION IN THE LABORATORY
we can demonstrate anaerobic respiration in the laboratory by a simple experiment. Let's see the complete activity. 
LAB ACTIVITY 
AIM: To  demonstrate anaerobic respiration in yeast 
APPARATUS (MATERIALS)REQUIRED:  A thermometer, bent tube, small test tube and a beaker , glucose solution, yeast powder, diazene green solution, liquid paraffin 
PROCEDURE: 
1. Make gucose solution by adding some sugar in a glass of water. 
2. Boil the glucose solution to remove the dissolved oxygen from it. Immediately cool it and add yeast powder. 
3. Add few drops of diazene green solution or Janus  green B solution. This dye changes the solution to pink in colour in the absence of oxygen. 
4. Now pour 1cm layer of liquid paraffin to stop the flow of oxygen into the solution. 
5. Cover the mouth of the test tube with a two holed rubber stopper. 
6. Through one hole pass thermometer to check the heat evolved and through another hole insert a bent tube whose other end should be in a beaker filled with lime water. 
7. Keep this set up for 7 to 8 hoursand observe. 
OBSERVATION: 
 We observe that the lime water changes to milky white in colour , a peculiar smell from the test tube and there is a rise in thermometer reading after 7 to 8 hours. 
RESULT : Based on the given observation we can say that yeast has undergone anaerobic respiration producing carbondioxide which changes lime water to milky white precipitate and heat is evolved during this process. And peculiar smell from the test tube  because of the ethyl alcohol formed during the respiration. 
 
This process of anaerobic respiration by yeast is also called as fermentation which is commercially used in making if alcoholic beverages like beer, champagne, etc 



 FERMENTATION:
 The process in which yeast converts the natural sugars present in cereals to ethyl alcohol and carbondioxide us called as fermentation. 


Comments

Post a Comment

Popular posts from this blog

Mohl's half leaf experiment

Image
Experiment to demonstrate Moll’s half-leaf experiment for showing that CO 2 , light, chlorophyll and water are necessary requirements for photosynthesis: Requirements: A potted plant, caustic potash, wide- mouthed bottle, iodine, split cork, water Method: 1. De-starch a potted plant by putting it in complete darkness for two days. 2. Fill partly a wide-mouthed bottle with strong solution of caustic potash and fit a split cork on its mouth. 3. Insert about half of the portion of a leaf of the de-starched plant into the bottle through the split cork (Fig. 36). 4. Place the whole apparatus in light after applying grease on the upper portion of split cork, and test the leaf for stach after about 10 hours. Observations: Portions of the leaf inside the bottle as well as in between the split cork show negative test for starch indicating the absence of photosynthesis while the portions outside the split cork show positive test for starch indicating the presence of process of photosynthesis in
Read more

EUTROPHICATION

Image
When water bodies such as lakes, estuaries and slow moving streams receive excess nutrients ,it results in excessive plant (algal) growth . This process is called eutrophication. This excessive growth of plants such as  Water hyacinth and algae reduces the dissolved oxygen (BOD- biological oxygen demand) in water. The water body then becomes incapable of supporting fishes and  other forms of aquatic life. Excessive growth of algae in such water bodies is described as algal bloom. Nitrates and phosphates are the two main substances(nutrients) that causes such condition, which is a direct result of pollution. These nutrients come from a variety of sources,such as fertilizers applied to agricultural fields and golf courses, excessive use if detergents, erosion of soil containing nutrients,untreated sewage and discharges from sewage treatment plants. EUTROPHICATION not only leads to reduced oxygen but also produce foul odour and slow death of water body. Thus, biodiversity in t
Read more

Hydrilla plant experiment

Image
Experiment to demonstrate that oxygen is evolved during the process of photosynthesis: Answer Requirements: Beaker, water, test tube, funnel, Hydrilla plant. Method: 1. Fill the beaker with the water and take an aquatic plant, such as Hydrilla, in the beaker. 2. Cut the bases of the plants, tie them with a thread and cover them with an inverted funnel in such a fashion that the cut ends of plants are towards the neck of the funnel.  3. Fill a test tube with the water and invert it on the upper end of the funnel. 4. Keep the whole apparatus in sunlight and observe for some time. Observations: From the cut ends of the plant some bubbles are coming out continuously and they are collected at the top of the test tube by displacing the water.  Test for the gas: To test the gas released, bring a burning match stick near the mouth of the test tube which would burst into flames. This shows that the gas released is oxygen.  Results: The liberated gas is oxygen and it is evolved due to the photol
Read more