respiration of animals is an reversible change or irreversible change ?

Cellular respiration occurs in both plants and animals. This reaction is reversible.


  Glucose + O2 -----------> ATP ------------> ADP + Phosphate + energy


The majority of animals respire through aerobic respiration, which means that they take up oxygen and produce carbon dioxide through oxidation. On the contrary, there are also some microorganisms which respire without free oxygen. This is known as anaerobic respiration or fermentation. This anaerobic respiration is reversible process.


During Aerobic respiration due to the presence of oxygen, the chemical energy of glucose is released gradually in a series of enzyme-controlled reactions.

  Glucose + Oxygen -----------> ATP + Carbon Dioxide + Water

  C6H12O2 + 6O2 ---------> 38 ATP + 6CO2 + 6H2O

  The glucose molecule is more completely broken down releasing 38 molecules of ATP per molecule of glucose used.


i.e. Glucose -------------> Pyruvic acid  + 2 ATP


Pyruvic acid-----------> 36ATP + 6CO2 + 6H2O


During most types of anaerobic respirations (insufficient oxygen), glucose is gradually broken down in a series of enzyme-controlled reactions to either lactic acid (in animals) or alcohol and CO2 (in plants). Glucose molecule is not completely broken down, and only 2 molecules of ATP are released per molecule of glucose used.  Hence aerobic respiration is more efficient than anaerobic respiration.


i.e. Glucose -------------> Pyruvic acid + 2 ATP


Pyruvic acid -----------> Lactic acid ( NO ATP) [in animals]


In animals, under anaerobic conditions, the glucose is converted into lactic acid. No molecules of ATP are generated. If lactic acid is exposed to oxygen, it will be converted back into pyruvic acid. Hence the cells can then use lactic acid in the aerobic pathway. The quantity of oxygen required to convert all the lactic acid formed by

anaerobic respiration back to pyruvic acid is known as the oxygen debt.


Lactic acid -----------> Pyruvic acid


Pyruvic acid-----------> 36ATP + 6CO2 + 6H2O  [oxygen debt occurs – aerobic path occurs]

Anaerobic respiration in animal cells is said to be reversible.

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It is reversible.

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It is irreveseble

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