Category : 7th Class

*       Introduction


Often a question arises in our mind, why does our body take food, air and water? What does our body do with these substances? Our body takes food, water, and air to serve mainly the following purposes:

(a) To full fill the energy requirement of the body;

(b) For growth of the body;

(c) To repair the damaged parts of the body;

(d) To fight against the pathogens.


*      Respiration

Respiration can be termed as the production and utilization of energy. It fulfills the energy requirement of the living body. In winter days, you might have seen people burn woods to get heat energy to keep the body warm. Similarly our body burns glucose inside the cell to get energy, which is required to perform various functions. Our body performs many metabolic procedures. Each metabolic procedure requires energy to be performed. It is the respiration that supplies the required energy. Look at the following equation:

Glucose (Digested food) + Oxygen \[\to \] Carbon dioxide + Water + Energy

\[{{C}_{6}}{{H}_{12}}{{O}_{6}}+6{{O}_{2}}\to 6{{H}_{2}}O+6C{{O}_{2}}+\]

Energy The life appeared on the Earth about 3.8 billion year ago, when there was no oxygen \[({{O}_{2}})\] in the atmosphere. It is an evidence that early life could survive without oxygen. Some microorganisms have the ability to perform the respiration even in the absence of oxygen. On this basis, respiration has been classified into two types, which has been discussed below.  


*           Types of Respirations

There are two types of respiration, aerobic respiration and anaerobic respiration. When digested food (glucose) is burnt in the presence of oxygen in order to obtain energy, it is called aerobic respiration. And when digested food (glucose) is burnt in the absence of oxygen in order to obtain energy, it is called anaerobic respiration.


Comparison between aerobic and anaerobic respiration

Aerobic respiration Anaerobic respiration
Respiration which is performed in the presence of oxygen Respiration which is performed in the absence of oxygen
Production of more energy Production of comparatively less energy
End products are carbon dioxide, water and energy End products are Lactic acid, ethanol, carbon dioxide, and energy
Ex: Plants and animals Ex: Some microorganisms


*            Anaerobic Respiration in Human

When we do vigorous exercises, we feel tired and our muscles as heavy. This is because of the formation of lactic acid in the muscle cells. During vigorous exercises cells of our muscle work hard and their energy requirement increases to a great extent. To meet the energy demand, heart starts to pump blood fast. But as the demand of energy is very high, the cells start to burn glucose in absence of oxygen, which causes formation of lactic acid.


Look at the following equation:

Glucose \[\to \] Lactic acid + Energy

\[{{C}_{6}}{{H}_{12}}{{O}_{6}}\to 2{{C}_{3}}{{H}_{6}}{{O}_{3}}+\] Energy 


*             Anaerobic Respiration in Plant

When roots of terrestrial plants are surrounded by water, air trapped in between soil particles is expelled out or dissolved in water. As a result root cells find insufficient air, and in such a condition they start anaerobic respiration.

Glucose \[\to \] Carbon dioxide + Ethanol (alcohol) + Energy

\[{{C}_{6}}{{H}_{12}}{{O}_{6}}\to 2C{{O}_{2}}+2{{C}_{2}}{{H}_{5}}OH+\] Energy





     Which kind of requirement of a living body is served by the process respiration?

(a) Water requirement

(b) Food requirement

(c) Energy requirement

(d) Defence requirement

(e) None of these


Answer: (c)



       When glucose is oxidized in absence of oxygen which one of the following may be the end product?

(a) Lactic acid

(b) Ethanol

(c) Carbon dioxide

(d) All of these

(e) None of these


Answer: (d)


You need to login to perform this action.
You will be redirected in 3 sec spinner