Difference Between Aerobic Respiration and Fermentation

Introduction

You know that all the activities performed by the body require energy. Where does the body get energy from? - The food that we eat contains energy. Now the question arises, how is the energy stored in food released to be used by the body? - Prokaryotic and Eukaryotic organisms use the respiration process as a mechanism for breaking down food that may require oxygen, to obtain energy. You must know that during the activity of breathing, we take in air (oxygen). Oxygen gets circulated to all cells of the body. Glucose found in food is broken down in the cells with the help of oxygen.

The process in which food is broken down in the cells to release energy is known as Cellular respiration. The activity of the breakdown of food (glucose) in the presence of oxygen is known as Aerobic respiration. It is the process by which food is dispersed in the cells with the assistance of oxygen. Fermentation is the process in which a substance disperses into an uncomplicated form.

Aerobic Respiration vs Fermentation

Initially, let's discuss the similarity between Aerobic respiration and Fermentation. Both 'Aerobic Respiration' and 'Fermentation' use glycolysis and glucose in their processes. Their procedures get conducted within the cells with the goal of energy production.

The primary difference between 'Aerobic Respiration and Fermentation' is that Aerobic Respiration is a metabolic process that conducts in the presence of oxygen whereas, Fermentation is a catabolic process that occurs in the absence of oxygen. Both have the same purpose of generating energy, but the procedures are different.

We will discuss in detail regarding the differences between Aerobic respiration and Fermentation further.

Difference Between Aerobic Respiration and Fermentation in Tabular Form

Parameters of Comparison	Aerobic Respiration	Fermentation
Definition	Aerobic respiration breaks the respiratory materials into simpler material, using oxygen.	Fermentation breaks substances anaerobically (without oxygen).
Oxygen Utilisation	Aerobic respiration gets conducted in the presence of oxygen.	The fermentation process does not require air or oxygen.
Location	Its process takes place in the cytoplasm and mitochondria of the cell.	Fermentation transpires in the cytoplasm of the cell.
End Products	The end products in Aerobic respiration are carbon dioxide, water, and energy in the form of ATP.	The end products in the fermentation process are ethanol, lactate, carbon dioxide, and heat.
ATP molecules	During the process, 38 ATP molecules are manufactured.	During Fermentation, 4 ATP molecules are produced.
Oxidation	Aerobic respiration includes complete oxidation of the respiratory substance.	Incomplete oxidation of respiratory material takes place in Fermentation.
Procedure	It is a four-step procedure: Glycolysis, Pyruvate oxidation Krebs cycle, and Oxidative phosphorylation.	It consists of two steps: Glycolysis and incomplete dispersion of pyruvic acid.
Water	Water is formed in Aerobic respiration.	Water is not formed during Fermentation.
Energy production	In Aerobic Respiration, 686 kcal per gram mole of glucose of energy is produced.	In Fermentation, only 40-60 kcal of energy is produced per gram mole of glucose.
Example	The examples include all multicellular organisms – humans, animals, plants, insects, and so on.	Wine, beer, yoghurt, pickles, bread, biofuels, and kimchi.

What is Aerobic Respiration?

There are two categories of cellular respiration - Aerobic and Anaerobic.

Aerobic Respiration uses oxygen for breaking down the material into a simpler substance. It is a form of cellular respiration that requires oxygen to produce energy. 

Aerobic Respiration is the procedure of producing energy by the oxidation of nutrients. The process of originating energy in the form of ATP (Adenosine triphosphate) from glucose molecules in the presence of oxygen involves a series of complex reactions that take place in the procedure explained below. But before that, we need to discuss ATP.

ATP or Adenosine triphosphate is the root of energy for utilisation and storage at the cellular level. ATP is similar to storing money in the bank.

Stages of Aerobic Respiration

1. Glycolysis - Glycolysis is the first step of Aerobic Respiration, which involves extracting energy from glucose. Two molecules of pyruvate, ATP, water, and NADH get yielded during this process. This process gets conducted in the cytoplasm of the cell. Pyruvate, deemed to be a three-carbon-containing compound, gets converted into a two-molecule compound after this step. The two pyruvate molecules contain the energy that the glucose molecule bore. 
2. Pyruvate Oxidation - This stage involves the conversion of pyruvate into carbon dioxide and a two-carbon molecule. This results in the production of NADH, which could be utilised in the manufacturing of ATP. 
3. The Krebs cycle - The two-carbon-molecule enters the Krebs cycle. This cycle includes nine different reactions. In the first step of this cycle, citric acid or citrate gets manufactured. Two more ATP molecules get extricated, and a multitude of electrons results in getting eliminated.
4. Oxidative phosphorylation - This is the main energy-providing stage. In this activity, the energetic electrons carried by the electron carriers (NADH) are utilised for yielding a huge sum of ATP. The electron transport chain contains proteins and organic molecules. This step requires oxygen. Without oxygen, the production of ATP would not be possible.

These processes aid in the production of energy from glucose molecules. In Aerobic respiration, glycolysis continues with the Krebs cycle.

Equation of Aerobic Respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38ATP

(glucose + oxygen →carbon dioxide + water + energy)

Aerobic respiration requires glucose and oxygen and it yields carbon dioxide, water, and energy as end products. The equation describes the reactants and their products inclusive of glycolysis. During the process, energy is released by breaking the glucose or carbohydrate. This energy is used to generate ATP molecules that are used by organisms for various purposes. All green plants synthesize their food and release energy with the assistance of the photosynthesis process.

Importance of Aerobic Respiration

• Aerobic Respiration is a process in which many organisms produce energy using oxygen and food. It gives rise to carbon dioxide that our body needs to release.
• Food and oxygen are required to produce ATP that helps our cells in functioning. It is because of Aerobic respiration that we need both food and oxygen.
• Aerobic respiration provides energy to all the cellular procedures that happen in our bodies.
• ATP, produced during the process, is used for other life-sustaining activities, for instance, growth, maintenance and repair.

Role of Oxygen in Aerobic Respiration

The role of oxygen is limited, although Aerobic respiration occurs only in the presence of oxygen. The presence of oxygen is essential as it operates the whole process of removing hydrogen from the organism's body. It acts as the final hydrogen acceptor. Oxygen plays a vital role, as in respiration, it is the energy of oxidation and reduction that gets utilised for the production of protein gradient.

What is Fermentation?

Louis Pasteur (French chemist and microbiologist) first coined the term to describe the transformations emanated by Yeast and microorganisms in the absence of air. He realised that carbon dioxide and ethanol are not the only by-products of fermentation.

• Fermentation is a process which includes breaking down a substance into a simpler substance, anaerobically (without oxygen).
• Fermentation can also be defined as the degradation of carbohydrates into simpler molecules by processes involving oxi-do-reduction but not requiring molecular oxygen. 

It refers to a group of chemical reactions induced by microorganisms to transform sugar into carbon dioxide and ethanol. The sugar initially goes through glycolysis, where it gets fragmented into two pyruvate molecules. The pyruvate is oxidised to ethanol or lactic acid. 

Fermentation can be divided into two processes: 

• Lactic acid fermentation - It leaves lactate as a by-product. It is used in pickles, cheese, and yoghurt. Lactic acid fermentation occurs when tissues need more energy.
• Ethanol fermentation - It leaves ethanol and carbon dioxide as a by-product. It is utilised to produce wine, beer, biofuel, bread, etc.

Equations of Fermentation

For Lactic acid fermentation: 

C₆H₁₂O₆ (Glucose) → 2 CH₃CHOHCOOH (Lactic acid)

For Ethanol fermentation:

C₆H₁₂O₆ (Glucose) → 2 C₂H₅OH (Ethanol) + 2 CO₂ (Carbon dioxide)

History of Fermentation

• The use of Fermentation can be traced as early as the Neolithic age and has been documented from - 7000 to 6600 BCE in China, 6000 BCE in Georgia, 5000 BCE in India (Ayurveda), 3150 BCE in ancient Egypt, 2000 BCE in Mexico, 3000 BCE in Babylon, and 1500 BC in Sudan. 
• The Baltic God Rugutis was known as the agent of fermentation. Fermented foods are said to have religious importance in Christianity and Judaism.
• Charles Cagniard de la Tour, Theodor Schwann and Friedrich Traugott Kützing published papers in 1837 stating that yeast is a living organism. Chemists like Antoine Lavoisier continued to consider fermentation as a mere chemical reaction and rejected yeast as being a living organism.
• Louis Pasteur's experiments during the 1850s and 1860s were the turning point. He displayed that fermentation is initiated by living organisms. His work and discovery led to the formation of the process of pasteurisation.
• Another milestone was when Eduard Buechner, a German chemist, ground up yeast and extract juice from them. To his amazement, he found out that this would yield a sugar solution forming carbon dioxide and alcohol.

Fermentation in Plants and Animals

Fermentation is an anaerobic process in which energy is produced from glucose or sugar. Fermentation transpires in bacteria, yeast, plants, and muscle cells of animals. Fermentation in animal muscle cells is known as Lactic acid fermentation because the end product is Lactate. Lactic acid fermentation occurs in the muscle cells while performing vigorous activity.

In plant cells, it is called alcoholic fermentation, as the end products are ethanol and CO₂. Pyruvic acid converts into ethanol and carbon dioxide, and NADH yields NAD+.

Importance of Fermentation

• Fermentation is the process that makes bread fluffy and soft. Yeast is used primarily in baking as a leavening agent for the fermentation process. Yeast converts carbohydrates into carbon dioxide, carbon dioxide helps in the production of tiny air pockets in the dough, and these tiny air pockets cause the dough to rise and expand.
• Fermented foods and drinks undergo controlled microbial growth and fermentation. These products have a unique aroma, taste, and texture. Yeast and other bacteria convert sugar into alcohol, heat, and carbon dioxide when making alcoholic drinks. Fermented food and drinks are also helpful in digestion- Probiotics and yeast help in maintaining your digestive system healthy.
• Alcoholic fermentation and heat are used to break down carbohydrate molecules in plants in making biofuels. Ethanol is a biomass-based renewable fuel that is manufactured by fermenting sugar.
• Production of biopolymers requires specific nutrients and suitable surroundings. Fermentation plays a chief role in their production.
• Fermentation is also used in pharma products- Microbial fermentation helps amalgamate a variety of medicines like vaccines, antibiotics, and others.  
• Fermented foods are rich in Vitamin C, Vitamin K, Vitamin B, Zinc, and Iron. Thus, Fermented foods ensure that your body receives vitamins and minerals.

Main Differences Between Aerobic respiration and Fermentation In Points

• In Aerobic Respiration, oxygen aids in deriving energy from substances. In Fermentation, oxygen is not required to derive energy.
• Aerobic respiration occurs primarily in higher organisms, whereas fermentation occurs mainly in microorganisms.
• In Aerobic Respiration, the type of phosphorylation involved is both oxidative and substrate. In Fermentation, only substrate-level fermentation occurs.
• The final electron acceptor in aerobic respiration is the oxygen molecule. In the case of fermentation, the final electron acceptor is an organic molecule such as pyruvic acid.
• Glucose is oxidised completely into carbon dioxide during aerobic respiration; Glucose is not oxidised entirely into ethanol or lactic acid and carbon dioxide.

Conclusion

Fermentation and Aerobic Respiration are two different processes for producing ATP for the cell to function. The former occurs in the absence of oxygen, and the latter requires oxygen to produce ATP.

Aerobic respiration is more efficient than fermentation in terms of ATP net formation. In aerobic respiration 38 ATP molecules are manufactured, and in fermentation, only 4 ATP molecules are produced.

To conclude, Fermentation is the breakdown of organic substances into alcohols, organic acids, carbon dioxide, etc. with the assistance of microorganisms, in the absence of oxygen. Aerobic Respiration is the release of energy in cells due to the breakdown of food material in the presence of oxygen.

References

• https://www.britannica.com/science/fermentation
• https://www.biologyonline.com/dictionary/aerobic-respiration