Q.Respiratory Quotient value of Anaerobic respiration is infinity. Why?

Because anaerobic respiration uses no oxygen at all, the denominator of the RQ formula (O2 consumed) becomes zero, while CO2 is still produced — making the ratio mathematically infinite.

Respiratory Quotient (RQ) is defined as:

RQ = (volume of CO2 evolved) / (volume of O2 consumed)

This ratio is normally used to indicate which respiratory substrate (carbohydrate, fat, or protein) is being oxidized in aerobic respiration, since it depends on how much oxygen is needed relative to the CO2 released for a given substrate (e.g., RQ = 1 for carbohydrates, RQ < 1 for fats and proteins).

However, in ANAEROBIC respiration (fermentation), the process does not use molecular oxygen (O2) at all — for example, in alcoholic fermentation, pyruvate is decarboxylated to acetaldehyde (releasing CO2) and then reduced to ethanol using the NADH generated in glycolysis, without any O2 being consumed anywhere in the pathway.

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