CBSE Biology Experiment to Show that Carbon Dioxide is Given out During Respiration

Biology experiment - Experiment Showing that Carbon Dioxide is Given out During Respiration

When you think of the word 'respire', you probably think of breathing. In breathing, you are taking in oxygen and releasing carbon dioxide. This gaseous exchange is important for respiration, but while breathing is a physical process, respiration is more of a chemical process. All organisms, from a single bacterial cell to plants to a blue whale, undergo respiration.

Respiration takes place in all types of living cells, and it’s called cellular respiration. Energy stored in glucose is released during respiration and without it, these cells would die. There are two types of respiration:

• Aerobic respiration occurs in the presence of oxygen, in most cells most of the time.

• Anaerobic respiration occurs without oxygen.

Some of the energy liberated during the breakdown of the glucose molecule is in the form of heat, but a large part of heat energy is converted into chemical energy released by these ATP molecules.

Table of Content

•  Aim

• Theory

• Material Required

•  Procedure

• Observation

• Results

•  Precautions 

Aim

To experimentally show that carbon dioxide is given out during respiration.

Theory

Living organisms obtain their energy from the food material by the method of cellular respiration. Most of the organisms are aerobic wherein, oxygen is used to break-down glucose entirely into carbon dioxide and water and simultaneously release energy in the process. Organisms like yeast and certain bacteria can respire in the absence of oxygen by a process known as anaerobic respiration. In this process, glucose is converted to ethanol, and carbon dioxide and energy are released. This process of respiration in some microorganisms under oxygen depriving conditions is called fermentation. In this experiment, we are going to study the process of fermentation and the liberation of heat and carbon dioxide gas.

Materials Required

• Test tube

• Delivery tube

• Yeast 

• Sugar solution

• Paraffin wax

• Lime water

• Thermometer

• Thermos flask

Procedure

Step 1. Take some sugar solution in a test tube and keep it for a minute to remove the oxygen in it and cool it.

Step 2. Pour this sugar solution into the thermo flask.

Step 3. Add some yeast to the sugar solution.

Step 4. The presence of oxygen in the solution can be tested by adding a few drops of diazin green to the solution. The blue colour solution of diazin green turns pink if oxygen is absent in the solution.

Step 5. Pour liquid paraffin into the solution.

Step 6. Insert the thermometer and one end of the delivery tube into the Thermos flask and another end of the delivery tube into the conical flask containing lime water (as shown in the image).

Step 7. Leave the experimental set-up for 2 hours. Observe the mercury level of the thermometer and the appearance of lime water.

Experimental setup showing that carbon dioxide and heat are liberated during respiration

Observations

After two hours, we observe that the mercury level has risen due to the release of heat and the lime water turned milky white due to the absorption of carbon dioxide.

Result

The increase in the level of mercury in the thermometer indicates that carbon dioxide is produced during anaerobic respiration. The yeast respire and produce carbon dioxide, which is absorbed by the lime water and creates a milky appearance.

Precautions

1. There should be no air gaps while pouring paraffin wax.

2. Keep the conical flask clean.

3. Fix the end of the delivering tube in a Thermo flask so it becomes airtight.

4.  Use freshly prepared lime water solution.

Lab Manual Questions

1. What is the difference between aerobic and anaerobic respiration?

Ans: The differences between these two types of respiration are listed below:

• Aerobic respiration: It is the breakdown of glucose in the presence of oxygen.

• Anaerobic respiration: It is the breakdown of glucose in the absence of oxygen.

2. What is the role of lime water in this experiment?

Ans: Lime water solution absorbs the CO2 released during respiration and creates white turbidity.

3. How can you prove that heat is liberated during respiration?

Ans: The increase in the level of mercury in the thermometer indicates that carbon dioxide is produced during respiration.

4. Why do we use yeast in this experiment?

Ans: Yeasts undergo fermentation and convert carbohydrates into carbon dioxide.

Viva Questions

1. What is respiration?

Ans: The process of breakdown of food in the cell with the release of energy is called respiration.

2. What are the types of respiration?

Ans: There are two types of respiration: Aerobic and Anaerobic respiration.

3. What is anaerobic respiration?

Ans: When Respiration takes place in the absence of oxygen, it is known as anaerobic respiration. This process is also called fermentation.

4. What is the end product of anaerobic respiration?

Ans: The end products of anaerobic respiration are carbon dioxide, ethanol, and ATP molecules.

5. Name the energy currency of the cell.

Ans: The energy currency of the cell is ATP molecules.

6. Name two respiratory mediums for living beings.

Ans: Air and water are the two respiratory mediums.

7. Name some industrial products of fermentation.

Ans: Acetic acid, Citric acid, and Ethanol are products of fermentation.

8. Define RQ.

Ans: The RQ is the ratio of carbon dioxide production to oxygen consumption.

9. How does the use of lime water help to show that carbon dioxide is released during respiration in the above experiment?

Ans: Lime water solution absorbs the carbon dioxide released during respiration  and creates white turbidity.

10. Why is less energy released during anaerobic respiration?

Ans: Because the glucose molecules are partially broken down.

Practical Based Questions

1. Anaerobic respiration is

1. Intramolecular respiration

2. Molecular respiration

3. Intermolecular respiration

4. Intra-molecular respiration

Ans: D. Intra-molecular respiration

2. Anaerobic respiration is also called as

1. Fermentation

2. Respiration

3. Aerobic respiration

4. None of them

Ans: A. Fermentation

3. Which of the following processes is common for aerobic and anaerobic respiration?

1. Glycolysis

2. Krebs cycle

3. TCA cycle

4. None of these

Ans: A. Glycolysis

4.  Which is a product of anaerobic respiration?

1. Pyruvic acid

2. Citric acid

3. Ethyl alcohol/lactic acid

4. None of the above

Ans: C. Ethyl alcohol/lactic acid

5. R.Q. of anaerobic respiration is:

1. Zero

2. Infinity

3. Less than two

4. More than five

Ans: B. Infinity

6. Which of the following physiological processes does not require water as a reactant?

1. Anaerobic respiration

2. Digestion of dietary protein

3. aerobic respiration

4. photosynthesis

Ans: A. Anaerobic respiration

7. Substances that yeast cannot produce by anaerobic respiration are:

1. CO2

2. Pyruvate

3. Lactic acid

4. Alcohol

Ans: C. Lactic acid

8. Which of the following is true for anaerobic respiration?

1. Glucose + lactic acid = carbon dioxide + water

2. Glucose= Lactic acid + carbon dioxide

3. Glucose gives lactic acid

4. None of the mentioned

Ans: C. Glucose gives lactic acid

9. Compared with aerobic respiration, the main characteristic of anaerobic respiration is:

1. Decompose organic matter

2. release energy

3. Requires enzymes to catalyse

4. Incomplete decomposition of organic matter

Ans: D. Incomplete decomposition of organic matter

10.  The kind of respiration through which skeletal muscles of the human body get the energy is:

1. acidic respiration

2. anaerobic respiration

3. aerobic respiration

4. nitrogenous respiration

Ans: B. anaerobic respiration

Summary

Lime water solution absorbs the carbon dioxide released during the respiration of yeast, which creates white turbidity in the conical flask, causing a milky appearance in the lime water of the test tube. The rise in the level of mercury in the thermometer shows that heat is released during respiration.