What is the major difference between respiration and anaerob

What is the major difference between respiration and anaerobic respiration? Which metabolic option would yield more energy, and why?

Solution

Ans. The fundamental difference between respiration (aerobic cellular respiration) and anaerobic respiration is that aerobic respiration used O₂ as terminal electron acceptor during electron transport chain (ETC) whereas the later does not.

Both aerobic and anaerobic respiration has root at glycolysis – the common pathway to them.

Under aerobic conditions, pyruvate (end-product of glycolysis) further enter tricarboxylic acid cycle and ETC through various intermediates. During ETC, the high-energy electron of glucose (being carrier by molecules NADH and FADH₂) is finally given to O₂ to form water simultaneously with production of cellular energy. 1 mol glucose produces (net gain) around 30 mol ATP through aerobic respiration.

Under anaerobic conditions, pyruvate (end-product of glycolysis) enters fermentation pathways like lactose fermentation, ethanol fermentation, etc. There is no ATP production during fermentation pathways. However, these pathways regenerate NAD⁺ , so that glycolysis keeps going on. Therefore, net gain from 1 mol glucose during anaerobic respiration is only 2 ATP (that is, ATP gain of glycolysis).

Therefore, aerobic respiration produce more ATP (30 ATP) than anaerobic respiration (2 ATP). It is because aerobic respiration completely oxidizes glucose (or, other substrates) into CO₂ and H₂O and harvest its energy into maximum possible ATP gain under physiological conditions. The end-product of anaerobic respiration (ex- ethanol, lactate produced through fermentation) have partially released their energy during glycolysis, but the major fraction still retained by them. That’s why, ethanol and lactate have still have higher energy content (i.e. more energy can be harvested from them, say through combustion that leads to their complete oxidation) than end products of aerobic respiration (CO₂, H­₂O- no more energy can be harvest from these end products).