What is the Difference Between Anaerobic Respiration in Plants and Animals

The key difference between anaerobic respiration in plants and animals is that the end products in the anaerobic respiration of plants are ethanol and carbon dioxide, while the end product in the anaerobic respiration of animals is lactic acid.

Cellular respiration is a metabolic process that takes place in the cells of living organisms. It is a set of biochemical reactions that convert chemical energy from nutrients or oxygen molecules into adenosine triphosphate (ATP). This process releases waste products as well. The most common nutrients that are used by plant and animal cells in respiration include sugar (glucose), amino acids, and fatty acids. Moreover, cells use molecular oxygen as the usual oxidizing agent, which provides most of the chemical energy. There are mainly two types of respiration as aerobic and anaerobic, based on the presence and absence of molecular oxygen. Anaerobic respiration in plants and animals is a process where respiration takes place in the absence of molecular oxygen.

CONTENTS

1. Overview and Key Difference
2. What is Anaerobic Respiration in Plants 
3. What is Anaerobic Respiration in Animals
4. Similarities – Anaerobic Respiration in Plants and Animals
5. Anaerobic Respiration in Plants vs Animals in Tabular Form
6. Summary – Anaerobic Respiration in Plants vs Animals

What is Anaerobic Respiration in Plants?

Anaerobic respiration is the process of releasing energy in an enzymatically controlled stepwise manner based on the absence of molecular oxygen. It is also defined as the incomplete degradation of organic food without using oxygen as a proper oxidant. Anaerobic respiration is the exclusive mode of respiration in some parasites, prokaryotes, and several unicellular eukaryotes. The end products in the anaerobic respiration of plants are ethanol and carbon dioxide. Because of the production of ethyl alcohol, it is also known as alcoholic fermentation. Due to the production of carbon dioxide, it gives a frothy appearance to the media at the end of the reaction.

Furthermore, two known enzymes participate in this process. Pyruvate decarboxylase is the first cytoplasmic enzyme that converts pyruvate to acetaldehyde by removing one CO₂ molecule. Coenzyme thiamine pyrophosphate (TPP) is also used in this reaction.  Later, the enzyme alcohol dehydrogenase converts acetaldehyde into ethyl alcohol. For the above purpose, hydrogen is obtained from NADH, which is produced during glycolysis. Normally, 2ATP are produced through this type of anaerobic respiration. Moreover, the accumulation of alcohol beyond a certain limit can damage plant cells.

What is Anaerobic Respiration in Animals?

Anaerobic respiration in animals takes place in muscle cells in the absence of molecular oxygen. The end product in the anaerobic respiration of animals is lactic acid. Therefore, it is also known as homolactic fermentation. Lactic acid produced in muscle cells is directly sent to the liver to regenerate glucose. Generally, in lactic acid fermentation, the pyruvic acid produced in glycolysis is directly reduced by NADH to form lactic acid.

There is no CO₂ gas production in this reaction. The enzyme that catalyzes this reaction is lactic dehydrogenase, which requires coenzyme FMN (flavin mononucleotide) and cofactor Zn²⁺. Furthermore, 2ATP are generated through anaerobic respiration in animals (lactic acid fermentation).

What are the Similarities Between Anaerobic Respiration in Plants and Animals?

• Anaerobic respiration in plants and animals take place in the absence of molecular oxygen.
• In both processes, two ATP are produced.
• Both processes involve an incomplete breakdown of the respiratory substrate.
• In these processes, the NADH produced in glycolysis is often used.
• Electron transport chain is absent in both processes.
• They are both enzyme-catalyzed reactions.

What is the Difference Between Anaerobic Respiration in Plants and Animals?

The end products in the anaerobic respiration of plants are ethanol and carbon dioxide, while the end product in the anaerobic respiration of animals is lactic acid. So, this is the key difference between anaerobic respiration in plants and animals. Moreover, CO₂ released from the reaction causes foaming in the anaerobic respiration of plants but not in the anaerobic respiration of animals.

The following infographic lists the differences between anaerobic respiration in plants and animals in tabular form for side by side comparison.

Summary – Anaerobic Respiration in Plants vs Animals

Anaerobic respiration in plants and animals is a process where respiration takes place in the absence of molecular oxygen.  In anaerobic respiration, the cells do not use molecular oxygen as an oxidizing agent. Moreover, the anaerobic respiration of plants is a process that produces ethanol and carbon dioxide as end products. On the other hand, anaerobic respiration of animals is a process that produces lactic acid as an end product. Thus, this is the key difference between anaerobic respiration in plants and animals.

Reference:

1. “Anaerobic Respiration in Plants.” Biology Discussion, 17 Aug. 2016.

Image Courtesy:

1. “Alcoholic Fermentation” By Lisawerner9 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Lactic Acid Fermentation” By Lisawerner9 – Own work (CC BY-SA 4.0) via Commons Wikimedia