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Difference Between Respiration and Combustion

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Distinguishing Respiration and Combustion

In this article, we will learn the major differences between combustion and respiration which will help students to get a good grasp on both topics.


What is Respiration?

Respiration is the mechanism by which all living organisms generate the energy they require to survive. Because this occurs within the cells, it is also known as cellular respiration. Typically, two gases are exchanged: oxygen and carbon dioxide. The cells use oxygen and expel carbon dioxide. Aerobic respiration is the name for this type of breathing. In some situations, breathing can occur without the use of oxygen. Anaerobic respiration is the term for this process. Fermentation is another name for it.

  • Cellular respiration is the process by which nutrients get converted into useful energy in a cell.  

  • It is a biochemical process where energy is released stepwise as the chemical bonds break in stages.  

  • It liberates less than 50 per cent of energy as heat. 

  • In very few cases, it liberates light. 

  • Temperature doesn’t rise and most of the energy is trapped in the form of ATP molecules. 

  • At the end of the reaction between oxygen and coenzymes, oxidation occurs during respiration.  

  • Respiration forms numerous intermediates which are used in the synthesis of different organic compounds. 

  • It takes place with the help of various enzymes and one enzyme is required for each step or reaction.

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What is Combustion?

Combustion is a chemical reaction that produces heat and light in the form of flame and is frequently accompanied by the release of oxygen. The pace at which the reactants combine is high, partly due to the nature of the chemical reaction and partly due to the fact that more energy is generated than can escape into the surrounding medium, causing the temperature of the reactants to be elevated to speed up the reaction even more.

  • A non-cellular and uncontrolled process where energy is released in a single step by burning substances is called combustion. 

  • It is a physicochemical process where chemical steps occur simultaneously rather than step-wise. 

  • It liberates most of the energy as heat.

  • It also produces light and the temperature becomes very high during this process.

  • This process doesn't include ATP generation.

  • Here, the substrate is directly oxidized in combustion without the production of any intermediates. 

  • It is a burning process that doesn't require any enzyme.

From the dawn of time, people have been observing and speculating about combustion, fire, and flame. Every society has come up with its own explanation. Combustion was explained by the Greeks in terms of philosophical concepts, one of which was that all combustible bodies had an "inflammable principle," which existed when the body was burned to react with air.

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Difference Between Respiration and Combustion



Glucose is broken down in living cells with the process called respiration. 

Combustion of substances such as wood and kerosene releases lots of energy. 

Inside the cells, many chemicals participate in the long chains of reactions to break down glucose into simpler substances, and the energy released in different steps is saved in the form of ATP.

It is not a process taking place inside our cells.

It takes place in a controlled manner inside the cells.

It is an uncontrollable process.

Heat is produced in cellular respiration. For example, the rate of respiration increases when we exercise and we feel warmer.

It produces energy as waste and heat.

It is much more efficient.

It is less efficient as compared to the respiration process.

Different chemicals break glucose step by step.

Heat breaks down glucose

It produces a large amount of energy stored as chemical energy.

It produces energy wasted as heat.

If the temperature is allowed to rise, the cell may damage.

The temperature during combustion can be very high and usually higher than respiration.

One of the examples is aerobic respiration that occurs in the presence of oxygen; and in life processes, glucose and oxygen are converted to carbon dioxide, water, and energy from respiration. 

Its examples are Combustion of oxygen and hydrogen leading to the formation of water vapour; when we ignite the gas stove for cooking food; motor vehicles burning petrol and diesel for motion; burning wood for fire and producing heat.

Respiration uses glucose to give pyruvate and then carbon dioxide. 

Any substance which can burn leads to a combustion process.

ATP is the byproduct of respiration as energy is trapped in the form of ATP in respiration.

It produces heat energy which is instantly utilized.

There is no smoke formation.

It produces oxides as smoke formation takes place.


Similarities Between Respiration and Combustion

It is good to know the differences between respiration and combustion; however, what are the similarities between these two that makes us compare the two and talk about the differences. Let’s explore!

  1. Both combustion and respiration involve the burning of the substrate.

  2. In both of these processes, the substance undergoes oxidation (in presence of oxygen).

  3. Both of these liberate energy.

  4. Both have some by-products in the form of oxides.

Last updated date: 22nd Sep 2023
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FAQs on Difference Between Respiration and Combustion

1. Explain respiration and combustion with an example of sugar.

During respiration, the charring of sugar doesn’t occur as it takes place inside body cells whereas in combustion the sugar is melted, chars, and then burns to produce the flame.

2. How is the energy released during combustion and respiration?

The energy is released in the form of ATP and heat in respiration while the energy is released in the form of heat in combustion.

3. Is it true that breathing is a form of combustion?

Slow combustion can be seen in cellular respiration as one example. Glucose is oxidized in the process of respiration, which releases carbon dioxide and energy. This is a combustion-like process.

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