Difference Between Respiration and Combustion

Bookmark added to your notes.
View Notes

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 in both the topics. 


  • 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 percent energy as heat.

  • In a 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.


  • 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 temperature becomes very high during this process.

  • This process doesn't include ATP generation.

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

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

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 breakdown 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 the cellular respiration. 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 waste as heat.

If 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 is converted to carbon dioxide, water and energy from respiration. 

Its examples: Combustion of oxygen and hydrogen leading to the formation of water vapour; when we ignite the gas stove for cooking food; motor vehicle 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 utilised.

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 make 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 of the by-products in the form of oxides.

FAQ (Frequently Asked Questions)

1. Differentiate Between Respiration and Combustion.

Respiration is a slower process than combustion. Respiration occurs at the body temperature whereas combustion takes place at a high ignition temperature. Fuel for oxidation reaction in respiration is food whereas fuel for oxidation reaction in combustion is usually hydrocarbons. During respiration, the oxidation reaction is always complete and the products formed are carbon dioxide, water and energy. On the other hand, the oxidation reaction may not be complete and the reaction products may cause pollution due to the presence of carbon monoxide and  unburnt carbon particles. 

2. Explain Respiration and Combustion with an Example of Sugar.

During respiration, 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 flame. 

3. 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.