1. How do the body derive energy for its various activities? How do living things get oxygen?

The living things get energy of their life  activities by the oxidation of nutrients.

They receive oxygen from the atmospheric air taken in during inspiration.

2. Explain the term "respiratory surface".

In respiration a surface is needed for the exchange of gases. This surface is called respiratory surface.

3. How does exchange of gases take place in respiration?

In respiration exchange of gases takes place through diffusion.

4. How does the difference in the concentration of respiratory gases in the protoplasm inside the unicellular organism, the water surrounding them help in exchange of gases?

The concentration of oxygen in the water surrounding the organism is greater than that in the protoplasm inside. So oxygen diffuses from the surrounding to the protoplasm.

5. Even though tracheal respiration is the most efficient mechanism in respiration, it is not seen in higher animals, Why is it so?

Tracheal method of respiration is not successful in tracheal tubes of more than two centimetres in length. Therefore tracheal system is not seen in higher animals. Even in large insects, tracheal tubes of more than two centimetres long are not seen.

6. What is "turbulence precipitation"?

Obstructions and folds in the nasal passage create turbulence of air. When air strikes these obstructions thedust particles in he air gets adhered to the mucous. This is called "turbulence precipitation".

7. How does coughing and sneezing clean the respiratory tract (passage)?

Trachea, bronchi and bronchioles are very sensitive to dirt, dust and such other substances. As soon as these substances reach these regions, coughing starts and dust is expelled out.

The dust particles that reach the nostrils and nasal passages are expelled out by sneezing.

8. What is glycolsis?

 The glucose that reaches the cell is converted to pyruvic acid in the cytoplasm. This chemical reaction that occurs in the absence or without the involvement of oxygen called  glycolysis.

9. What is Kerb's cycle? Where does it happens?

The series of reactions involved in the step-wise degradation of pyruvic acid occurs in a cycle known as Kreb's cycle. It occurs in the mitochondria in the presences of different enzymes and oxygen. As a result, energy contained in them is released to synthesize ATP.  CO₂ and H₂O are formed as by products.

 The glucose that reaches the cell is converted to pyruvic acid in the cytoplasm. This chemical reaction that occurs in the absence or without the involvement of oxygen called  glycolysis.

10. Why is ATP considered as a currency in the energy exchange process?

ATP splits into ADP and phosphates are releases energy. As a battery is recharged, ADP gets converted to ATP, with the energy produced by oxidation of food. In this sense, ATP is considered as a currency in the energy exchange process.

11. What is aerobic respiration?

Aerobic respiration occurs in the presence of molecular oxygen. The oxygen completely oxidises the food to carbon dioxide and water, releasing large amount of energy.

C₆H₁₂O₆ + 6O₂ +  → 6CO₂ + 6H₂O + 2880KJ
(glucose)    (oxygen)          (carbon   (water)   (energy)
                                             dioxide)

12. What is anaerobic respiration?

Anaerobic respiration occurs in the absence of molecular oxygen and is also called fermentation. Here food is only partially oxidised so only a part (5%) of the energy is released. The rest of energy remains trapped in the intermediate compounds.

13. Name a few organisms that respire anaerobically.

Yeast, parasitic worms like tape worm, hook worm.

14. It two plants are kept in a dark room an a well ventilated room, what changes will occur in the air in two rooms?

The amount of CO₂ will be more in the dark room as photosynthesis will not take place in the absence of light.

The amount of CO₂ and O₂ will be almost equal because photosynthesis and respiration will be taking place at the same rate.

15. What is diffusion? How should the respiratory surface suitable for diffusion of gases?

Diffusion is the process of movement of molecules from a region of higher concentration to a region of lower concentration.

For the diffusion of gases the respiratory surface must be

Permeable
Thin - for diffusion takes place only through a membrane, the thickness of which is 1mm or less than that.
having a great surface area.
having s fluid medium.

16. Which are the causative micro organisms that effect the fermentation of milk an dough?

Milk changes to curd, and fermentation on dough are anaerobic respiration. The first change is due to the respiration of an anaerobic bacteria called lactobacillus. The second change is due to the anaerobic respiration of yeast.

17. What is the difference between breathing and respiration?

Most higher organisms have three respiratory processes:

a) Breathing, by which the animal draws the air or oxygen from the environment into the respiratory organisms  b) transport of oxygen absorbed into its respiratory organs or in body fluids to the whole of the body, and c) respiratory exchange between the body fluids and the tissue cells. For convenience sake, all these three respiratory processes together are called the external respiration, while the decomposition inside the cell for the release of energy are called the cellular or the internal respiration. Thus respiration includes two processes - External respiration or breathing and internal respiration or cellular respiration.

18. Differences between aerobic and anaerobic respiration.

19.  Which are the energy molecules in a cell? How do these molecules liberate energy?

The energy molecule in a cell is ATP (Adenosine tri phosphate)

ATP provides energy for olife activities. It splits into ADP (Adenosine disphosphate) and phosphate and releases energy.

ATP             ADP + iP + energy
                      (inorganic phosphate)

20. How do plants help in maintaining the ratio of oxygen and carbon  dioxide in the atmospheric air?

The respiration of plants and animals causes decrease in oxygen and increase in carbon dioxide content of air. During photosynthesis plants consume carbon dioxide and gives out oxygen. Decrease of oxygen due to breathing is balanced by photosynthesis. Thus plants help in maintaining the ratio of oxygen and carbon dioxide in the atmospheric air.

21.  How are food particle prevented from entering the trachea?

During swallowing a cartilaginous lid called epiglottis, (which guards the glottis) closes the glottis to prevent the entry of food into the trachea.

22. Which are the two main phases of cellular respiration? How do they differ?

The two main phases of cellular respiration are

1. Glycolysis
2. Kreb's cycle