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The conversion of chemical energy in the form of glucoseinto useable energy in the form of ATP is referred to as cellular respiration. It is divided into two types: aerobic respiration, which happens when oxygen is present, and anaerobic respiration, which occurs when oxygen is absent.

Glycolysis, Krebs cycle, and oxidative phosphorylation come under aerobic respiration to convert glucose into ATP. The following is the net response for aerobic respiration:

${\text{C}}_{\text{6}}{\text{H}}_{\text{12}}{\text{O}}_{\text{6}}{\text{+ 6O}}_{\text{2}}→{\text{6CO}}_{\text{2}}{\text{+ 6H}}_{\text{2}}\text{O + Energy}$

The energy or ATP yield by the reaction is 36 or 38 molecules of ATP.

In the absence of oxygen, anaerobic respiration involves the conversion of glucose into ATP, with the ultimate acceptors of electrons being sulfate, nitrate, sulfur, and fumarate. The following is the net response for aerobic respiration:

${\text{C}}_{\text{6}}{\text{H}}_{\text{12}}{\text{O}}_{\text{6}}→{\text{2C}}_{\text{2}}{\text{H}}_{\text{5}}{\text{OH + 6CO}}_{\text{2}}\text{+ Energy}$

The energy or ATP yielded by the reaction is only 2 molecules of ATP.

The molecular acceptor of electrons generated during glucose oxidation in aerobic respiration is oxygen, with a high affinity for electrons. So, aerobic respiration is a highly efficient process with a high ATP yield and higher reaction rate.

However, anaerobic respiration has a lower reaction rate and ATP productionbecause the acceptor for electrons generated during glucose oxidation is molecules other than oxygen, such as nitrate, sulfates, and other molecules with poor affinity for electrons.