Question

How do aerobic respiration and fermentation compare with respect to the efficiency of energy production?

Answer 1

Hint: Aerobes is a world of aerobic organisms, we tend to consider the aerobic respiration “better” than fermentation. In some of the ways it is. However, anaerobic respiration has persisted far longer on this planet, through major changes made in atmosphere and life. There must be value in this alternative way of making those ATP.

Complete answer:
A major argument in favour of aerobic over anaerobic respiration is the overall energy production. Without using oxygen, organisms can only break 6-carbon glucose into two 3-carbon pyruvate molecules. As we have seen earlier, glycolysis releases only enough energy to produce two (net) ATPs per molecule of the glucose.
Aerobic respiration, on the other hand, which produces ATP more slowly. It does, however, break glucose all the way down into Carbon dioxide, producing around 38 ATPs. Membrane transport (active transport) costs can slightly reduce this theoretical yield, but aerobic respiration consistently produces at least 15 times as much ATP as anaerobic respiration.
This vast increase in energy production eventually explains why aerobic organisms have come to dominate life on earth. It does also explain how organisms were able to increase in size, adding multicellularity and great diversity.
Fermentation does not involve any electron transport system, and actually, no ATP is made by the fermentation process directly. Fermenters usually make very little ATP—only two ATP molecules per glucose molecule during glycolysis.
Microbial fermentation processes have been used for the production of many foods and pharmaceuticals, and the identification of microbes.

Note: During lactic acid fermentation, pyruvate accepts electrons from NADH and is reduced to lactic acid. Microbes performing homolactic fermentation produce only lactic acid as the fermentation product; microbes performing heterotactic fermentation produce a mixture of lactic acid, ethanol and/or acetic acid, and Carbon dioxide.