The word respiration is derived from the Latin ‘respirare’ meaning to breathe. Generally, respiration is the physio-chemical process which leads to the chemical breakdown of materials to provide energy for life. It occurs inside the living cells of all types of organisms (from prokaryotic bacteria and Achaeans to eukaryotic protests, fungi, plants, and animals) to carry out various vital activities like growth, movement, reproduction, etc. In this process, organisms exchange gases between their body cells and the environment.
Respiration occurs in the three steps such as external, internal and cellular respiration. External respiration is the process of breathing (inhalation and exhalation) which is also known as ventilation whereas internal respiration is the process where the distribution of gases occurs between body fluids (blood) and tissues. By the internal respiration, oxygen (O2) is utilized by the tissues and liberates carbon dioxide (CO2) and energy.
Cellular respiration
Cellular respiration is an important process, which involves the conversion of food to energy. In this process, organisms breakdown glucose from food to create energy, known as adenosine triphosphate (ATP). There are two main types of cellular respiration:
Aerobic Respiration
It is the process which takes place in the presence of oxygen. In this process, complete oxidation occurs resulting in the end products of carbon dioxide (CO2) water (H2O) and energy. This respiration system is generally common in all multi-cellular organisms such as plants and animals, etc.
Anaerobic Respiration
It is the process where incomplete oxidation occurs in the absence of oxygen (O2). In this process, the end products are ethyl alcohol (C2H5OH) and carbon dioxide (CO2) in plants and lactic acid [CH3CH (OH) CO2H] in animals.
Difference between Aerobic and Anaerobic Respiration
Some important differences between aerobic and anaerobic respiration are stated in the following table:
| Aerobic Respiration | Anaerobic Respiration |
|---|---|
|
Aerobic respiration occurs in the presence of oxygen (O2). |
Anaerobic respiration occurs in the absence of oxygen (O2). |
|
In this case, glucose breakdown to produce more amount of energy. |
Glucose breakdown to produce less amount of energy. |
|
It occurs in the cytoplasm to mitochondria of the cell. | It occurs in cytoplasm of the cell only. |
| In this case, 38 ATP are released. | Only 2 ATP are produced. |
|
In this case, final products are Carbon dioxide (CO2) and water (H2O). |
Final products are Lactic acid [CH3CH (OH) CO2H] in animal cells, carbon dioxide (CO2) and ethanol (C2H5OH) in plant cell. |
| This process involves three stages: (i) glycolysis, (ii) electron transport and oxidative phosphorylation and (iii) Krebs cycle or citric acid cycle. |
It involves two stages: (i) glycolysis and (ii) fermentation. |
|
It is a long process for the production of energy. | Comparatively, it is a fast process. |
|
It shows complete process of combustion. |
It shows incomplete process of combustion. |
|
It occurs in multi-cellular organisms such as plants, animals and humans (eukaryotes). |
It occurs in mainly unicellular organisms bacteria, fungi, yeast protozoa, etc (prokaryotes). |
Some Similarities between Aerobic and Anaerobic Respiration
- The glycolysis occurs in both the aerobic and anaerobic respiration.
- Adenosine Triphosphate (ATP) is released in both the aerobic (38 ATP) and anaerobic respiration (2 ATP).
- In both the aerobic and anaerobic respiration, glucose converts to pyruvic acid within all the tissues.
Factors Affecting Respiration
The respiration process is affected by several external and internal factors:
External Factors:
Oxygen (O2): Rate of respiration directly varies with the oxygen (O2) concentration.
Temperature: The rate of respiration increases with the rise of temperature up to a certain limit which ranges from 0 0C-45 0C but above 45 0C the rate falls and finally the respiration comes to a standstill.
Carbon dioxide (CO2): The rate of respiration varies inversely with the concentration of carbon dioxide (CO2). But the higher concentration of CO2 leads to accumulation of more sugar, a respiratory substrate, may result in an increase of the respiration rate.
Water (H2O): The rate of respiration becomes rapid due to proper hydration of cells in the presence of adequate water supply.
Light: In most cases, the effect of light appears to be indirect for respiration. Light increases the synthesis of respiratory substrates by photosynthesis.
Injury: Generally, the respiratory rate increases in the place of injury. This is due to the accumulation of sugar around those injured plant tissues.
Chemical Substances: Substances like chloride of different metals such as Sodium (Na), Potassium (K), Magnesium (Mg), Calcium (Ca), etc. have an outstanding effect on the respiratory rate.
Internal Factors
Protoplasm: The rate of respiration is directly related to the amount of protoplasm in the cells undergoing respiration. Higher rate of respiration is seen in meristematic cells containing an adequate amount of protoplasm.
Respiratory Substrate: The respiratory rate becomes rapid with increasing concentration of respirable food materials under other favorable conditions.
Significance of Respiration
Respiration plays an important role in a living organism due to several reasons which are stated below:
- Respiration process leads to the formation of important cell constituents.
- It helps to change insoluble food to soluble food.
- It helps to maintain carbon balance in nature.
- It activates the different meristems of the plant body.
- Energy is released during this process which is used in performing various life processes.
- The respiratory system aids in breathing in the animal.
- Through the process of external respiration, oxygen (O2) is exchanged for carbon dioxide (CO2) waste inside the lungs.
- Through internal respiration, the bloodstream delivers oxygen (O2) to cells and removes waste carbon dioxide (CO2).
Concluding Remarks
Respiration is a nonstop process in all living organisms, and the organism cannot survive without respiration on the earth. Energy is an essential factor to perform various activities like growth, movement, reproduction, etc. The energy is gained by the breakdown of nutrient inside the cell within the body of all kinds of living organisms through the process of aerobic and anaerobic respiration. In this process, organisms also exchange gases between their body cells and the environment.
Also read: Cell Structure and Functions