There are two types of Aerobic Respiration

• 1.       External Respiration

In this stage the organisms take the air (containing oxygen) into their bodies. This stage includes the transport of oxygen obtained from the inhaled oxygen to each cell of the body.

• 2.       Internal Respiration

The second stage, which is called internal respiration, consists of the oxidation of glucose, amino acid and fatty acids etc., with molecular oxygen. This respiration is also known as cellular respiration is also known cellular respiration as it occurs within cells.

In the internal or cellular respiration glucose and other compounds are passed through such enzymatic reactions, which release the chemical energy gradually in small amounts, with the help of which ATP molecules are.

There are two method of respiration in the organisms.

Anaerobic Respiration

Some organisms oxidize their food without using any molecular oxygen. This is known as anaerobic respiration.

In this type of respiration considerably less amount of energy is produced as compared with the other type of respiration. It is also called fermentation.

In anaerobic respiration, a glucose molecule is broken down into two molecules of lactic acid with a release of only 47,000 calories of energy.

Glucose→2Lactic acid+ Energy (47,000 calories)

        i.            Holic Fermentation

In primitive cells and in some eukaryotic cells such as yeast, Pyruvic acid is further broken down by alcoholic fermentation into alcohol (C2H5 OH) and

CO₂

2(C₃H₄O₃)       2(C₂H₅OH)  +    2CO₂

Pyruvic acid       Alcohol

      ii.            Actic acid fermentation

In lactic acid fermentation, each Pyruvic acid molecule is converted in to lactic acid C₃ H₆ O₃ in the absence of oxygen gas.

2(C₃H₄O₃)     +      4H      2(C₃H₄O₃)

Pyruvic acid                          Lactic acid

Both alcoholic and lactic acid fermentation yield about 2% of the energy present within the chemical bonds of glucose, which is converted into adenosine triphosphate (ATP).