Difference Between Aerobic Glycolysis and Anaerobic Glycolysis (With Table)

Glycolysis is the first stage in the process of cellular respiration in all lifeforms. Within any form of life, there are two types of cellular respiration: aerobic and anaerobic respiration. Glycolysis happens in both kinds of respiration. This reaction occurs in the cytosol and is responsible for the breakdown of glucose into two pyruvate molecules.

Aerobic Glycolysis vs Anaerobic Glycolysis

The main difference between aerobic glycolysis and anaerobic glycolysis is that aerobic glycolysis happens when O2 and H2 atoms bind together to break down glucose and promote energy exchange, while anaerobic glycolysis takes place when glucose is broken down in the absence of O2.

Aerobic Glycolysis is a metabolic mechanism that converts monosaccharides, primarily C₆H₁₂O₆, into 2 molecules of C2H4O3. It creates 6 molecules of Nicotinamide adenine dinucleotide, 2 molecules of GTP, and 2 molecules of flavin adenine dinucleotide in the presence of oxygen, which is then oxidatively phosphorylated. This method is substantially more effective and produces significantly more Adenosine triphosphate per glucose molecule.

When there is a shortage of oxygen, anaerobic glycolysis breaks down glucose (C6H12O6) to lactate (O2). It occurs in a cell’s cytoplasm when the cell lacks an oxygenated atmosphere or lacks mitochondria. It is necessary for tissues with high energy needs, limited oxygen supply, or a lack of oxidative enzymes.

Comparison Table Between Aerobic Glycolysis and Anaerobic Glycolysis

Parameters of Comparison  Aerobic GlycolysisAnaerobic Glycolysis
Environment RequirementAerobic glycolysis takes place in an oxygen-rich environment.Anaerobic glycolysis takes place in an oxygen-deficient environment.
OccurrenceOccurs within a eukaryotic cell.It generally will occur in both prokaryotic and eukaryotic cells.
Proceeds ThroughAerobic glycolysis proceeds via the Kreb Cycle and oxidative phosphorylation.It proceeds through ethanol fermentation or lactic acid fermentation
End ProductsCarbon Dioxide (CO2) and Water (H2O).Lactic acid (C3H6O3) or ethanol (C2H5OH).
CofactorsGenerates two GTPs, six NADH, and two FADH2s, which are then oxidatively phosphorylated.Only four NADH molecules are formed, and they are replenished by substrate-level phosphorylation.

What is Aerobic Glycolysis?

Aerobic glycolysis is a glycolytic process that takes place in the presence of oxygen in the cytosol. As a result, it causes aerobic respiration, which is a form of cellular respiration that occurs in the presence of oxygen. The Krebs cycle and oxidative phosphorylation are the two successive phases of aerobic respiration. Aerobic glycolysis exclusively occurs only in eukaryotic cells.

Pyruvate, the final product of aerobic glycolysis, is transported to mitochondria to initiate the citric acid cycle. As an outcome, 34 Adenosine triphosphate molecules, water, and CO2 are the end products of aerobic glycolysis.

Aerobic glycolysis is also known as the Warburg Effect, which happens when C6H12O6 is turned to lactate in the presence of oxygen. When O2 is insufficient or cells are conducting aerobic glycolysis, NADH transforms pyruvate to lactate instead of reoxidizing it in mitochondria via oxidative phosphorylation. Ultimately, this lowers the overall ATP production in aerobic respiration. The clinical importance of aerobic glycolysis, on the other hand, arises within cancer stem cells in a tumour. As a result, excessive aerobic glycolysis has been linked to deadly cancer.

What is Anaerobic Glycolysis?

When there is no oxygen available, anaerobic glycolysis normally occurs. Anaerobic respiration happens as a result of this. Ethanol fermentation and lactic acid fermentation are two types of anaerobic respiration. Ethanol fermentation is mostly carried out in yeast, whereas lactic acid fermentation is carried out in mammals. Furthermore, in bacteria, lactate is substituted by other compounds such as propionate.

Additionally, in ethanol fermentation, pyruvate, the final product of glycolysis, is converted into C2H4O by pyruvate decarboxylase, releasing CO2. The enzyme alcohol dehydrogenase then transforms acetaldehyde into ethanol. Lactic acid fermentation happens in muscle cells in the absence of enough oxygen by turning pyruvate into lactate. Anaerobic glycolysis may happen in both eukaryotic and prokaryotic cells, and it can happen in the cytosol or the cytoplasm.

Lactate is produced during anaerobic glycolysis, which lowers the pH and inactivates the enzymes. Anaerobic glycolysis is assumed to be the predominant source of energy in earlier species before oxygen was abundant in nature, and hence represents a more primitive mode of energy generation in cells.

Main Differences Between Aerobic Glycolysis and Anaerobic Glycolysis

  1. Aerobic glycolysis occurs when there is oxygen present, whereas anaerobic glycolysis occurs when there is no oxygen present.
  2.  Aerobic glycolysis results in a substantially more efficient ATP generation pathway, producing 32 ATPs per glucose molecule, whereas anaerobic glycolysis results in a less efficient ATP production pathway, producing 2 ATPs per glucose molecule.
  3. Aerobic glycolysis occurs predominantly within eukaryotic cells, whereas anaerobic glycolysis generally occurs in both prokaryotic and eukaryotic cells.
  4. Anaerobic glycolysis produces lactate as the end product, which can be damaging to cells, whereas aerobic glycolysis produces water and carbon dioxide, which are not hazardous to cells.
  5. Aerobic glycolysis continues inside the mitochondria, whereas anaerobic glycolysis continues in the cytoplasm.
  6.  Aerobic glycolysis involves the Krebs cycle as well as oxidative phosphorylation, whereas anaerobic glycolysis involves either ethanol fermentation or lactic acid fermentation.
  7. Aerobic glycolysis converts the produced pyruvate to acetyl coenzyme A, whereas anaerobic glycolysis converts it to lactate or acetaldehyde.

Conclusion

Glycolysis is a ten-step metabolic process that converts a glucose (C₆H₁₂O₆) molecule into two pyruvate molecules. The two forms of glycolytic pathways seen in distinct cellular respiration routes are aerobic and anaerobic glycolysis. Both are, in particular, the first stages of each kind of cellular respiration. They begin with glucose then convert it into two pyruvate molecules simultaneously making two ATP molecules and two NADH molecules.

Aerobic glycolysis is a kind of glycolysis that takes place in the presence of oxygen. As a result, it causes aerobic respiration in eukaryotic cells. Hence, aerobic glycolysis results in much more efficient ATP generation.  Anaerobic glycolysis, on the other hand, is a type of glycolysis that happens in the absence of O2. Therefore, it results either in lactic acid fermentation or ethanol fermentation with very little ATP synthesis. As a result, the primary distinction between aerobic and anaerobic glycolysis is the necessity for oxygen and the ability to create ATPs.

References

  1. https://muse.jhu.edu/article/403868/summary
  2. https://cancerres.aacrjournals.org/content/10/2/77.short