Respiration is the process of releasing energy from food and this takes place inside the cells of the body. The process of respiration involves taking in oxygen (of air) into cells, using it for releasing energy by burning food, and then eliminating the waste products (carbon dioxide and water) from the body. Respiration is an essential for life because it provides energy for carrying out all the life processes which are necessary to keep the organisms alive.
The mechanism by which organisms obtain oxygen from the air and release carbon dioxide is called breathing. But on the other hand respiration is a complex process it includes breathing as well as the oxidation of food in the cells of the organism to release energy. Breathing is a physical process whereas respiration is a biochemical process of oxidation of food. Breathing process involves lungs of the organism whereas respiration involves the mitochondria in the cells where food is oxidised to release energy.
Procedure of how energy is released during respiration:
The energy produced during respiration is stored in the form of ATP (Adenosine Tri- Phosphate) molecules in the cells of the body and used by the organism as when required. To understand this we should know the meaning of ADP, ATP and Inorganic Phosphate. ADP is Adenosine Di- Phosphate; ATP is Adenosine Tri- Phosphate and Inorganic Phosphate is a substance which contains a phosphate group made up of phosphorous and oxygen.
(i) The energy released during respiration is used to make ATP molecules from ADP and inorganic phosphate.
This energy is stored in the cells in the form of ATP.
(ii) When the cells need energy, then ATP can be broken down using water to release energy.
The released energy by ATP is equivalent to 30.5 kJ/mole and is used to carry out all the endodermic reactions taking place in the cells and so, ATP is known as the currency of cells.
• Aerobic Respiration: The respiration which uses oxygen. In this process, the glucose food is completely broken down in to carbon dioxide and water by oxidation and this energy gets stored in the ATP molecules.
Thus, mitochondria are the sites of aerobic respiration in the cells.
• Anaerobic Respiration: The respiration which takes place without oxygen. In this, the microorganisms like yeast break down glucose (food) in to ethanol, carbon dioxide and releases energy.
Therefore, whole process of anaerobic respiration takes place in the cytoplasm of cells. So, we can say that all the cells do not use oxygen to produce energy. Fermentation of sugar can also be done by using anaerobic respiration of yeast.
Human beings obtain energy by aerobic respiration but sometimes anaerobic respiration takes place in our muscles during vigorous physical exercise when oxygen gets used up faster in the muscle cells than can be supplied by the human body.
The accumulation of lactic Acid in the muscles causes muscle cramps.
• There is one similarity between aerobic and anaerobic respiration and that is energy is produced by the breakdown of food like glucose. The main differences between them are explained below:
|Aerobic Respiration||Anaerobic Respiration|
|1. It takes place in the presence of oxygen.||1. It takes place in the absence of oxygen.|
|2. Complete breakdown of food occurs.||2. Partial breakdown of food occurs.|
|3. The end products in aerobic respiration are carbon dioxide and water.||3. The end products in anaerobic respiration may be ethanol and carbon dioxide (as in yeast plant) or lactic acid (as in animal muscles).|
|4. In this considerable amount of energy is produced.||4. Much less energy is produced.|
Various Modes of respiration in animals:
• In simple unicellular animals like Amoeba, respiration takes place by the simple diffusion of gases through the cell membrane. Most of the animals have, however, specific organs for respiration.
• The animals like earthworms which live in the soil use their skin to absorb oxygen from air and remove carbon dioxide. So, the respiratory organ in the earthworm is the skin.
• The aquatic animals like fish, prawns and mussels have gills as the respiratory organs which extract oxygen dissolved in water and take away carbon dioxide from the body.
• In the insects like grasshopper, cockroach, housefly and a mosquito, the tiny holes called spiracles on their body and the air tubes called tracheae are the respiratory organs.
• The respiratory organs of the land animals such as man (humans), birds, lizard, dog and frog etc. are the lungs. However, Frogs breathe both by lungs and skin.
Therefore, we can say that all the respiratory organs whether skin, gills, trachea or lungs have three common features:
• All the respiratory organs have a large surface area to get enough oxygen.
• All the respiratory organs have thin walls for easy diffusion and exchange of respiratory gases.
• All the respiratory organs like skin, lungs and gills have a rich blood supply for transporting gases. But only in tracheal system of respiration, air reaches the cells directly.
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