In case of anaerobic respiration which occur in absence of oxygen the efficiency of oxidation is low as less amount of energy is released during the process. About 2 ATP molecules are formed in anaerobic respiration. The end products are ethanol(yeast) or lactic acid(muscles).
Glucose (Broken down to) →Energy (ATP) + Ethanol + Carbon dioxide (CO2)
In this process, glucose is first broken down into pyruvic acid by the process of glycolysis. It occurs in ten steps utilising different enzymes. Then pyruvic acid is broken down into alcohol, CO2 with the release of energy.