Respiration is one of the metabolic processes that are common in all living organisms. Breathing is a physical process as we inhale oxygen and exhale carbon dioxide. This exchange of gas is necessary for respiration. Respiration is considered as a chemical process which takes place within the cells of organisms by breaking down the oxygen for the production of energy. Every living species, from a single bacteria cell to a powerful blue whale, go through respiration.

The food molecules that are absorbed after the digestion process are pieced down, and the energy released in this process are utilized in movement and physical functioning of the organisms. In simple words, respiration is defined as the biochemical process wherein the cells of a creature gain energy by inducing together glucose and oxygen, resulting in the liberation of carbon dioxide (CO2).

If you evaluate the equation of cellular respiration, it will be clear that reactants (aerobic respiration) are glucose and oxygen, while 6 molecules of carbon dioxide, 6 molecules of water, and ATP molecule are the end product respectively.

Types of Respiration

  • There are two types of respiration, aerobic and anaerobic.Aerobic respiration is a continuous process which takes place within the cells of animals and plants. This process can be simply explained with the help of the chemical equation:

C6H12O6 + 6O2  →  6CO2   +   6H2O +  ATP

Glucose + Oxygen → Carbon dioxide + Water +  Energy

  • Anaerobic respiration is a type of cellular respiration which takes place in the absence of oxygen to produce energy. The chemical equation for anaerobic respiration is

C6H12O6    →    2 C2H5O H +  2CO2   +    ATP

Glucose → Alcohol + Carbon dioxide + Energy

Phases of Respiration

Respiration occurs in the cytosol and around the plasma membrane in Prokaryotic cells. In eukaryotic cells, respiration takes place in the mitochondria which is also considered as the powerhouse of eukaryotic cells and membrane folds wherein the activities can be augmented.

It is very much similar to internal combustion of the car engine, wherein organic compounds and oxygen go in, while water and carbon dioxide comes out. The energy that is liberated powers the automotive(or cell).


The molecule of glucose (from food) falls apart into pyruvic acid which is oxidized to carbon dioxide and water, leaving two carbon molecules, known as acetyl-CoA. Two ATP molecules are produced in this procedure and take place in the cytosol.

Oxidative Phosphorylation

Phases of Respiration - Oxidative Phosphorylation

The electrons are dropped by the electron acceptors, that in turn pushes the H+ ions in higher concentration on one of the sides of the plasma membrane. This creates a gradient pressure and moves ATP synthase enzyme, making 32 ATP. Oxygen takes the spared electrons, that combines with leftover hydrogen to make water.

Citric Acid Cycle:

The acetyl-CoA from glycolysis is mixed into an existing chain of carbon and broken down subsequently, eliminating more carbon dioxide (byproduct) and release electrons that are mixed into the acceptor molecules. Two ATP molecules are created for every phase of this cycle and take place in the mitochondrial matrix.

Respiration in autotrophs

Respiration in autotrophs is antithesis in the process of photosynthesis. Here, carbon dioxide and water are taken in along with sunlight to make glucose and oxygen. The products of photosynthesis are utilized by the heterotrophs, which comes under organisms that cannot make their own food and depend on autotrophs for food. The byproducts (carbon dioxide and water) are consumed by photosynthesis.

To learn more about respiration with interactive video lessons, visit BYJU’S.

Practise This Question

Mucus production in nose is advantageous because it ____.