What is the Difference Between Aerobic and Anaerobic Process

The main difference between aerobic and anaerobic process is that in an aerobic process, molecular oxygen occurs inside the cell whereas, in an anaerobic process, molecular oxygen is absent inside the cell. Furthermore, the aerobic process is more efficient in the production of energy in the form of ATP while anaerobic process is less efficient in the production of energy.

Aerobic and anaerobic process are two types of cellular respiration which occur in different types of organisms.

Key areas Covered

1. What is an Aerobic Process
     – Definition, Process, Significance
2. What is an Anaerobic Process
     – Definition, Process, Significance
3. What are the Similarities Between Aerobic and Anaerobic Process
     – Outline of Common features
4. What is the Difference Between Aerobic and Anaerobic Process
     – Comparison of Key Differences

Key Terms

Aerobic Process, Anaerobic Process, ATP, Cellular Respiration, Final Electron Acceptor, Glucose, Glycolysis

What is an Aerobic Process

Aerobic respiration is a type of cellular process responsible for the production of ATP, which is the energy currency of the cell through the complete oxidization of glucose. Here, the carbon dioxide and water are the two types of by-products of this reaction. Significantly, aerobic respiration is the main form of cellular respiration method used by higher organisms including animals and plants.

Figure 1: Aerobic Process

Furthermore, the three main steps of aerobic respiration are glycolysis, Krebs cycle, and electron transport chain. Actually, glycolysis is the first step of the aerobic process responsible for the breakdown of glucose into two pyruvate molecules, producing 2 ATP and 2 NADH molecules. Then, this pyruvate undergoes oxidative decarboxylation to form acetyl-CoA, which enters into the Krebs cycle, occurring in the mitochondrial matrix. Here, the Krebs cycle is responsible for the complete breakdown of acetyl-CoA in carbon dioxide, producing 2 GTP, 6 NADH, and 2 FADH₂ molecules. Finally, the reducing energy in the molecules produced during the cellular respiration including NADH and FADH₂ is used to produce ATP by the oxidative phosphorylation of the electron transport chain, which occurs on the inner membrane of mitochondria. Molecular oxygen serves as the final electron acceptor, giving rise to water. More efficiently, aerobic respiration produces 36 ATP molecules per glucose molecule.

What is an Anaerobic Process

Anaerobic process is the other type of cellular respiration that occurs in the absence of molecular oxygen inside the cell. Significantly, this type of cellular respiration occurs in lower organisms including bacteria, yeast, and parasitic worms. Also, the first step of the anaerobic process is glycolysis, which occurs inside the cytoplasm. However, based on the fate of the pyruvate molecules, there are two types of anaerobic respiration as ethanol fermentation and lactic acid fermentation. Here, yeasts mainly undergo ethanol fermentation, which involves the conversion of pyruvate into an aldehyde, then converted into ethanol. However, lactic acid fermentation mainly occurs in bacteria. It involves the conversion of pyruvate into lactic acid. However, the regeneration of NAD⁺ in both types of fermentation does not produce ATP. Therefore, the complete yield of ATP is two, which is produced in the glycolysis.

Figure 2: Cellular Respiration

In contrast to fermentation, another type of anaerobic process occurs in several types of bacteria. And, this type of anaerobic respiration too proceeds through three steps: glycolysis, Krebs cycle, and electron transport chain. However, the final electron acceptor in the electron transport chain is not molecular oxygen, but inorganic compounds including ions like sulfate or nitrate and carbon dioxide. For example, methanogenic bacteria use carbon dioxide as the final electron acceptor, producing methane gas as a by-product.

Similarities Between Aerobic and Anaerobic Process

• Aerobic and anaerobic process are the two types of cellular respiration methods used in different types of organisms.
• Both processes break bonds in simple organic compounds and use the released energy to produce ATP.
• Furthermore, glucose is the main form of simple organic compound in both cellular respiration.
• Also, glycolysis, which occurs inside the cytoplasm, is the first step of these cellular respirations.
• Moreover, carbon dioxide is a byproduct of both processes.

Difference Between Aerobic and Anaerobic Process

Definition

Aerobic process refers to the cellular respiration process occurring in the presence of oxygen while anaerobic process refers to the cellular respiration process occurring in the absence of free oxygen. Thus, this is the main difference between aerobic and anaerobic process. 

Type of Organisms

Also, another important difference between aerobic and anaerobic process is that the aerobic process mainly occurs in higher organisms while anaerobic process mainly occurs in lower organisms including bacteria, yeast, and parasites.

Cellular Location

Moreover, one other difference between aerobic and anaerobic process is that the aerobic process occurs in the cytoplasm and inside the mitochondria while anaerobic process occurs in the cytoplasm.

Significance

The three steps of the aerobic process are glycolysis, Krebs cycle, and electron transport chain while the two main types of anaerobic process are the ethanol fermentation and lactic acid fermentation.

Chemical Reaction

Furthermore, the chemical reaction of the aerobic process is C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 36ATP while the chemical reaction of ethanol fermentation is C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2ATP and the chemical reaction of lactic acid fermentation is C₆H₁₂O₆ → 2C₃H₆O₃ + 2ATP.

Molecular Oxygen

Importantly, the aerobic process requires molecular oxygen inside the cell while the anaerobic process does not require molecular oxygen.

Substrate Oxidization

Besides these, while aerobic process is responsible for the complete oxidization of the substrate, anaerobic process is responsible for the incomplete oxidization of the substrate. Hence, this is another difference between aerobic and anaerobic process.

NAD⁺ Regeneration

Additionally, the NAD⁺ regeneration occurs in the electron transport chain of the aerobic process while the NAD⁺ regeneration occurs during the partial oxidization of pyruvate of the anaerobic process.

ATP Production during NAD⁺ Regeneration

Further, one more difference between aerobic and anaerobic process is that the NAD⁺ regeneration of the aerobic process produces ATP while the NAD⁺ regeneration of the anaerobic process does not produce ATP.

Number of ATP Produced

The aerobic process produces 36 ATP molecules per glucose molecule while anaerobic process produces only 2 ATP per glucose molecule. This is also a difference between aerobic and anaerobic process.

Water Production

Also, water production is one other difference between aerobic and anaerobic process. That is; aerobic process produces six water molecules per glucose molecule while anaerobic process does not produce water molecules as it does not use molecular oxygen in the electron transport chain.

Conclusion

Aerobic process is a type of cellular process that requires the presence of molecular oxygen inside the cell. Aerobic respiration is the main type of aerobic process, which breaks down the bonds in a glucose molecule to produce ATP by using the released energy. During aerobic respiration, 32 ATP molecules are produced per glucose molecule. In comparison, the anaerobic process is a type of cellular process which occurs in the absence of molecular oxygen. It produces fewer ATP molecules through the incomplete oxidization of glucose. Therefore, the main difference between aerobic and anaerobic process is the use of molecule oxygen for the process and efficiency.

References:

1. Scoville, Heather. “What Is the Difference Between Aerobic and Anaerobic Processes?” ThoughtCo, ThoughtCo, 2 Jan. 2019, Available Here.

Image Courtesy:

1. “Aerobic mitochondria process” By Boumphreyfr – Own work (CC BY-SA 3.0) via Commons Wikimedia  
2. “2505 Aerobic Versus Anaerobic Respiration” By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia