The key difference between lactic acid and alcoholic fermentation depends on the end products of each process. Lactic acid fermentation produces lactic acid as the end product while the alcoholic fermentation produces alcohol and carbon dioxide as the end products.
Respiration is an essential physiological activity of all living organisms by which they obtain energy for all metabolic activities of their body. The salient feature of respiration is the exchange of gases between the body and the environment. It is apparent in breathing or the external respiration. In reality, the fundamental exchange occurs in the cells of aerobic organisms, and it is the process called cellular respiration. However, certain organisms do not need oxygen for respiration. They are the anaerobic organisms such as certain microorganisms (Clostridium species) and parasitic worms (Ascaris), etc. Hence, they carry out anaerobic respiration in order to produce energy. There are two basic types of anaerobic respiration namely lactic acid fermentation and alcoholic fermentation. Compared to aerobic respiration, both these anaerobic processes produce a low amount of ATP from one glucose molecule. Therefore, they are less efficient processes.
CONTENTS
1. Overview and Key Difference
2. What is Lactic Acid Fermentation
3. What is Alcoholic Fermentation
4. Similarities Between Lactic Acid and Alcoholic Fermentation
5. Side by Side Comparison – Lactic Acid vs Alcoholic Fermentation in Tabular Form
6. Summary
What is Lactic Acid Fermentation?
Lactic acid fermentation is one of the two types of fermentation carried out by anaerobic bacteria such as lactic acid bacteria and muscle cells of animals. It occurs when the oxygen is not available. During the lactic acid fermentation, the produced pyruvate from glycolysis converts into lactic acid molecules. Hence, pyruvate does not undergo Kreb’s cycle or oxidative phosphorylation. Instead, it yogurt into lactic acid and produces a low amount of energy.
Figure 01: Lactic Acid Fermentation
The enzyme lactic dehydrogenase catalyzes the conversion of pyruvic acid into lactic acid. Furthermore, during this conversion, the reducing agent NADH converts into NAD+. The net gain of lactic acid fermentation is 2 ATPs per glucose molecule. Consequently, energy efficiency is about 41%.
What is Alcoholic Fermentation?
Alcoholic fermentation is the second type of fermentation that occurs under anaerobic conditions. It is an anaerobic respiration process that produces energy in the form of ATP in plants and some microorganisms such as yeasts, etc. Furthermore, this process takes place in two steps. Initially, pyruvate converts into two carbon acetaldehyde by removing a carboxyl group as a carbon dioxide molecule. Afterwards, the acetaldehyde converts into ethanol by taking electrons from NADH.
Figure 02: Alcoholic Fermentation
Here, the NADH converts into NAD+. Hence, alcoholic fermentation results in ethanol and CO2 as end products. The enzymes such as aspyruvic acid decarboxylase and alcohol dehydrogenase catalyze these reactions. Moreover, this process forms 2 ATP molecules per glucose molecule. Therefore, energy efficiency is about 29%.
What are the Similarities Between Lactic Acid and Alcoholic Fermentation?
- Lactic acid fermentation and alcoholic fermentation are anaerobic respiratory processes.
- Also, both pathways generate energy.
- Both happen under anaerobic conditions and produce a little amount of ATP (2ATP molecules from one glucose molecule).
- Furthermore, glycolysis is a common process in both processes.
- Moreover, NAD+ is the reducing agent and both regenerate this reducing agent.
- Besides, in both these processes, the end products are large organic compounds, which themselves are stores of energy.
What is the Difference Between Lactic Acid and Alcoholic Fermentation?
Lactic acid fermentation and alcoholic fermentation are two types of fermentation processes that occur under anaerobic conditions. Both processes produce energy, but a low amount of energy. However, the key difference between lactic acid and alcoholic fermentation is that the lactic acid fermentation results in lactate from glucose. Whereas, the alcoholic fermentation results in ethanol and carbon dioxide from glucose.
Furthermore, lactic acid fermentation occurs in animal muscle cells and bacteria while alcoholic fermentation occurs in plants and some microbes such as yeasts. So, this is another difference between lactic acid and alcoholic fermentation. Lactic acid fermentation is important in yoghurt and cheese production while alcoholic fermentation is important in bread, wine, beer and vinegar production.
Below infographic on the difference between lactic acid and alcoholic fermentation shows all these differences in detail.
Summary – Lactic Acid vs Alcoholic Fermentation
Fermentation is of two types; lactic acid fermentation and alcoholic fermentation. Both processes produce energy and occur under anaerobic conditions in the absence of oxygen. Also, both types of fermentation are industrially important. However, in summarizing the differences, the key difference between lactic acid and alcoholic fermentation is that the lactic acid fermentation results in lactate from glucose while alcoholic fermentation results in ethanol and carbon dioxide from glucose. Furthermore, lactic acid fermentation occurs in muscle cells of animals and certain microorganisms, while alcoholic fermentation occurs in plant tissues and some microorganisms.
Reference:
1. “Fermentation and Anaerobic Respiration.” Khan Academy, Khan Academy. Available here
2. “Ethanol Fermentation.” Wikipedia, Wikimedia Foundation, 28 Dec. 2018. Available here
Image Courtesy:
1.”Lactic acid fermentation”By Sjantoni – Own work, (CC BY-SA 3.0) via Commons Wikimedia
2.”Ethanol Fermentation english”By Arobson1 – Own work, (CC BY-SA 4.0) via Commons Wikimedia