Similarities & Differences between Respiration and Combustion

What are the Similarities & Differences between Respiration and Combustion ? – We are going to give answer of this question, so stay tuned with this article.

All organisms need energy to carry out their body activities. Plants also require it for a variety of metabolic activities which are of two types i.e. , anabolic and catabolic.


Before Similarities & Differences between Respiration and Combustion, you should know “What is Respiration and Combustion ?

So lets get started…

What is Respiration ?

Respiration is a catabolic process in which the living cells oxidise organic substances ( glucose ) with the help of oxygen ( aerobic ) releasing CO2 and water and energy or in the absence of oxygen ( anaerobic ) producing ethyl alcohol , CO2 and energy.

There are three important characters of respiration :

1. Breaking of glucose : It does not occur in single step but in a series of chemical steps. These steps occur in two major phases :

( a ) Glycolysis ( Glucose  Pyruvate ) occurring in cytoplasm

( b ) Krebs cycle ( Pyruvate  CO2 + H2O + ATP ) occurring in mitochondria.

2. Enzymes : Each breakdown step is due to a particular enzyme.

3. Energy in the form of ATP : Energy released in breakdown of glucose molecules is not all in the form of heat but a large part of it is converted into chemical energy in the form of ATP ( Adenosine triphosphate ) , the energy currency of cell.

This was all about the definition of respiration, lets discuss about “What is Combustion ?“.

What is Combustion ?

According to Wikipedia, Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke.

Combustion of an organic fuel in air is always exothermic because the double bond in O2 is much weaker than other double bonds , and therefore the formation of the stronger bonds in the combustion products CO2 and H2O results in the release of energy.

Similarities & Differences between Respiration and Combustion

Lavoisier pointed out that both respiration and combustion ( burning of coal , wood , oil , etc. ) are similar in several respects , but they also differ from each other.

Various similarities and differences between respiration and combustion are summarized below.

similarities between respiration and combustion

It was about similarities between Respiration and Combustion, lets discuss about their differences.

differences between respiration and combustion


Degradation of organic food for the purpose of releasing chemical energy can occur with or without the participation of oxygen. The former is called aerobic respiration and the later is called anaerobic respiration.

1. Aerobic or oxybiotic respiration : It is an oxygen dependent , enzymatically – controlled , complete , oxidative breakdown of respiratory substrates to CO2 and water with the release of energy.

C6H12O6 + 602 → 6CO2 + 6H2O + 38 ATP

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2. Anaerobic or anoxybiotic respiration : It is an oxygen independent , enzymatically – controlled , incomplete , breakdown of respiratory substrates to carbon dioxide and alcohol in plants and lactic acid in animals.

Almost all plants tested have the ability to carry out anaerobic respiration for shorter or longer periods. A simple chemical equation for anaerobic breakdown of glucose to alcohol and CO2 is as follows :

C6H12O6  2C2H5OH + 2CO2 + Energy ( 2ATP )


C6H1206 → 2CH2CH ( OH ) COOH + Energy

From the equations , it is clear that in anaerobic respiration no substance is added from outside.

It only involves the rearrangement of the atoms of glucose producing CO2 and ethyl alcohol ( alcoholic fermentation ) or lactic acid ( lactic acid fermentation ) releasing energy.

Therefore , this process is also called intra – molecular respiration.

similarities and differences between respiration and combustion


The aerobic oxidation of glucose is not a single step process. It involves a large number of steps which are grouped in the following four stages :

  • Glycolysis
  • Formation of acetyl Co – A
  • Kreb’s cycle
  • Terminal oxidation.

Glycolysis : It is an anaerobic process ( without the help of 02 ) that takes place in the cytoplasm of the cell. It is common in both the aerobic and anaerobic respirations , hence , also known as common pathway.

During glycolysis , one molecule of glucose is converted into two molecules of pyruvic acid in a series of reactions. Now , the pyruvic acid may enter into aerobic or anaerobic respiration.

Formation of acetyl Co – A : Three carbon compound – pyruvic acid is converted into two carbon compound – acetyl Co – A in the cytoplasm. Then it enters into the mitochondria for further oxidation.

Kreb’s cycle : This pathway was described by Sir Hans Krebs in 1937 , 1940 for which , he was awarded Nobel Prize in 1953.

It is also known as citric acid cycle or TCA ( Tricarboxylic acid cycle ). During this cyclical pathway acetyl Co – A is oxidised with the help of o , in a series of reactions producing CO2 and water.

Read about the process of Fertilization in Plants and Parts of a Flower and their Functions.

Terminal oxidation : During this pathway formation of ATP molecules takes place from ADP ( Adenosine Diphosphate ) molecules.

As the ATP molecules provide energy to carry out any activity in the cell , hence , these are called energy currency of the cell.


Respiration and photosynthesis are the two antagonistic and complementary processes in plants , involving gaseous exchanges. The substrates in one process are the end – products of the other process.

C6H1206 + 602  6CO2 + 6H2O + Energy

respiration and photosynthesis

The differences between respiration and photosynthesis are summarized as follows :

The process of photosynthesis is light – dependent. Since , the sunlight available during different parts of the day is not equal , hence , the rate of photosynthesis is not constant throughout the day.

The process of photosynthesis starts with sunrise in the early morning. With increasing intensity of light , the rate of photosynthesis increases. It soon becomes equal to the rate of respiration.

differences between respiration and photosynthesis

At this point the CO2 produced in respiration is consumed in photosynthesis and there is no gaseous exchange. This point is called compensation point.

The rate of photosynthesis exceeds the rate of respiration in the afternoon. As the light intensity is reduced in the evening , the rate of photosynthesis also decreases.

Read about the two main types of Plant Tissues.

It once again reaches at the compensation point. In the night , there is no photosynthesis and the plants release large amounts of CO2 due to respiration.


Title : Similarities & Differences between Respiration and Combustion

This article mainly contain about the similarities and differences between respiration and combustion. The following topics are covered briefly in this article :

  • What is Respiration ?
  • What is Combustion ?
  • Similarities & Differences between Respiration and Combustion
  • Types of Respiration
  • Respiration and Photosynthesis
Tags : Similarities & Differences between Respiration and CombustionSimilarities between Respiration and Combustion, Differences between Respiration and Combustion

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