Question

Give reasons for the following:

During anaerobic respiration, a 3-carbon molecule is formed as an end product instead of CO₂ in human beings.

Answer 1

1. In anaerobic respiration, which occurs in the absence of oxygen, the end product is not carbon dioxide \[\ce{(CO2)}\], but rather lactic acid (in humans) or ethanol and carbon dioxide (in some microorganisms).
2. Human cells generate lactic acid, a 3-carbon molecule, by anaerobic glycolysis when there is insufficient oxygen.
3. This method sustains ATP generation in the absence of oxygen. 
4. Lactic acid can cause transient muscle discomfort.
5. Anaerobic respiration in microorganisms such as yeast produces ethanol and carbon dioxide.