Difference Between Respiration and Combustion

The main difference between respiration and combustion is that respiration is a biochemical process in living cells to release energy, whereas combustion or burning is a chemical process that occurs outside the cell, releasing energy. 

Respiration and combustion are two processes that release energy. This energy is stored in ATP in respiration, while in combustion, the released energy is heat and light. 

Key Areas Covered

1. What is Respiration
– Definition, Facts, Features
2. What is Combustion
– Definition, Facts, Features
3. Similarities Between Respiration and Combustion
– Outline of Common Features
4. Difference Between Respiration and Combustion
– Comparison of Key Differences
5. FAQ – Respiration and Combustion
– Answers to frequently asked questions

Key Terms  

Cellular Respiration, Combustion, Respiration

Difference Between Respiration and Combustion - Comparison Summary

What is Respiration

Respiration or cellular respiration is the set of chemical reactions in a cell, converting biochemical energy into ATP. Although it is technically a combustion reaction, it occurs inside the cell, slowly releasing energy through a series of responses. Furthermore, nutrients used in respiration include sugar, amino acids, and fatty acids. Meanwhile, the main form of respiration is aerobic respiration, which uses oxygen as the final electron acceptor. During aerobic respiration, glycolysis breaks down nutrients into pyruvate, which enters into mitochondria to undergo complete oxidization into carbon dioxide and water. Moreover, the energy released by the chemical reactions is stored in ATP through the substrate-level phosphorylation of NADH and FADH2.

Differentiate Respiration and Combustion

Figure 1: Cellular Respiration 

Furthermore, in the absence of oxygen, respiration occurs through fermentation. Here, pyruvate produced in glycolysis converts into waste products in two processes known as lactic fermentation and ethanol fermentation. Moreover, anaerobic respiration is the type of respiration in microorganisms whose final electron acceptor is inorganic acceptors such as sulfates or nitrates.

What is Combustion

Combustion is a high-temperature, exothermic, redox reaction between a fuel and an oxidant. Usually, the oxidant is the atmospheric oxygen, while the mixture of gaseous byproducts is called the smoke. Here, heat and light are the forms through which the energy of the reaction is released. Generally, the combustion of solid fuels such as wood and coal proceeds through endothermic pyrolysis, which produces gaseous fuels undergoing combustion. Furthermore, the combustion of these gaseous fuels provides heat for producing more gaseous fuels.

Respiration vs Combustion

Figure 2: Combustion

Moreover, the combustion of an organic fuel in air is always an exothermic reaction. It is due to the higher bond strength of combustion products – carbon dioxide and water – compared to the bond strength in the double bond of oxygen. Furthermore, complete combustion is the type of combustion that results in zero fuel at the end of the combustion reaction. In contrast, in incomplete combustion, unburned products such as carbon monoxide, hydrogen, and even carbon in the form of ash may remain. 

Similarities Between Respiration and Combustion

  • Upcycle and recycling are two processes of reusing materials.
  • They are essential for going green and reducing carbon footprint.
  • Both processes conserve the environment.
  • They reform a product into a new product.
  • Both use oxygen and release carbon dioxide.

Difference Between Respiration and Combustion


Respiration refers to a process in living organisms involving energy production, typically with the intake of oxygen and the release of carbon dioxide from the oxidation of complex organic substances. In contrast, combustion refers to a rapid chemical combination of a substance with oxygen, involving the production of heat and light.


Respiration is a biochemical process, while combustion is a chemical process. 


Enzymes involve in respiration while enzymes do not involve in combustion. 

Formation of Intermediates

Respiration occurs through forming intermediates, while combustion does not form intermediates.

Energy Liberation

Respiration releases energy, forming ATP, while combustion releases energy, forming heat and light. 


Respiration occurs under physiological temperatures, while combustion occurs at high temperatures.

FAQ: Respiration and Combustion

Why is respiration called combustion? 

Respiration is called slow combustion. In respiration, food materials burn slowly at low temperatures and produce products such as carbon dioxide, energy, and water. 

What are the two types of combustion? 

Incomplete, complete, spontaneous, explosive, slow, and rapid combustion are the six types of combustion. A limited supply of oxygen in the air results in incomplete combustion, while a sufficient air supply results in complete combustion. 

Can combustion happen without oxygen? 

21% Of oxygen occurs in the air. But combustion requires 16% of oxygen. Combustion does not occur with no oxygen. 


In brief, respiration and combustion are two processes that release energy. Respiration is a biochemical process in which the energy stored in sugar is released from ATP. Also, it occurs under physiological conditions. In comparison, combustion is a chemical process in which the energy in solid fuel is released in the form of heat and light. Therefore, the reaction type is the main difference between respiration and combustion.     

  1. Respiration. Understanding Global Change. (2020, September 11).
  2. Encyclopædia Britannica, inc. (2023c, December 15). Combustion. Encyclopædia Britannica.
Image Courtesy:
  1. CellRespiration” By RegisFrey – Own Work (CC BY SA 3.0) via Commons Wikimedia
  2. Fire, Fireplace, Rostov-on-Don, Russia” By Vyacheslav Argenberg – Own Work (CC BY 4.0) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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