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Difference Between Endotoxins and Exotoxins for JEE Main 2024

Last updated date: 16th May 2024
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Toxins are small molecules, peptides, or proteins formed by living cells, when they come in contact or are ingested by tissues, may cause disease or structural damage.

Toxins and enzymes have a significant role to play in the pathogenicity of pathogenic bacteria. Toxins can help with invasiveness, destroy cells, disrupt cell processes or cause immune response and injury.

Toxins are of Two Types: Endotoxin and Exotoxin.

What is Endotoxin?

Endotoxin is a type of pyrogen, and a part of Gram - negative bacteria 's outer cell wall, such as E. Coli.

Endotoxin is a lipopolysaccharide. 

LPS consists of the lipid A portion – It contains fatty acids and disaccharide phosphates, core polysaccharides and the O-antigen. 

It is responsible for the molecule's endotoxin activity. It does not directly harm any tissue, the immune cells of humans and animals.

It indicates the presence of bacteria. Therefore, such cells stimulate a response intended to fend off unwanted intruders.

This reaction is completely inborn, which means no previous exposure to endotoxin is required. 

In fact, it can intriguingly serve to keep our healthy intestinal bacteria inside as much as to prevent large external entry of pathogenic bacteria.

Endotoxin Definition

The endotoxins are found in the bacteria's cell envelope or outer membrane, these are also cell - associated compounds that are responsible for the bacteria's structural components.

The LPS is found on the Gram - negative bacteria's outer surface, and becomes poisonous to the host to which it is attached under some circumstance.

Endotoxin examples: Vibrio cholera, E. coli, Shigella, Salmonella typhi.

What are Exotoxins?

Exotoxins are toxins that are released extracellularly with the organism 's development. Exotoxins are contagious toxins that spread to other parts of the body and cause damage from the focus of the infection.

They are proteins that act as enzymes and are soluble. An exotoxin is capable of causing host damage by destroying cells or interfering with the normal cell metabolism. 

Exotoxins are highly potent, and may cause the host significant damage. Exotoxins are excreted during rapid growth, or during cell lysis. Both gram positive and gram-negative produce exotoxins.

It’s not necessary that all exotoxins which are produced, harm humans. Some of them may be developed to play a role in bacterial physiology (resisting bacteriophages, regulating cellular function, or quorum sensing).

There are Three Main Types of Exotoxins:

  • Type I Toxins - Superantigens 

  • Type II Toxins - Exotoxins that damage host cell membranes.

  • Type III Toxins - A-B toxins and Other toxins which interfere with the host cell functions.

Exotoxin Definition

Exotoxins are generally secreted by bacteria and act either enzymatically or directly by the host cell. Bacteria release these into the surrounding area.

Exotoxins are proteins or polypeptides, most of which function at a tissue site away, from the original bacterial growth or invasion stage.

Exotoxin examples: Staphylococcus aureus, Bacillus cereus, Streptococcus pyogenes, Bacillus anthracis.

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Endotoxin Vs Exotoxin



These are part of the cells.

These toxins are released from the cell.

These are seen after the lysis of the gram-negative bacteria.

Present in the living gram-positive and gram-negative bacteria.

Molecular weight is 50-1000 KDa.

Molecular weight is 10 KDa.

Endotoxins are made up of Lipopolysaccharide.

Exotoxins are made up of Protein.

Endotoxins are stable to heat and seems to be active at 250° C and at 1000° C.

Exotoxins are destroyed at temperature beyond 60-80° C. since they are heat liable.

Endotoxin is not denatured on boiling

Exotoxin is denatured upon boiling

Immune reactions are Weak.

Immune reactions are strong.

Toxoids conversions are not possible.

Toxoid conversion is possible.

Fever occurs

Fever does not occur

It is detected by Limulus lysate assay.

It is detected by various test like neutralization, precipitation, etc

High enzymatic activity is seen.

No enzymatic activity is observed

endotoxins are non-specific.

exotoxins are specific to particular bacterial strain.

Antigenicity is poor.

Antigenicity is high.

FAQs on Difference Between Endotoxins and Exotoxins for JEE Main 2024

What is a Main Endotoxin and Exotoxin Difference?

Exotoxins are toxic substances that are released outside the cell and are secreted by bacteria. Whereas endotoxins are bacterial toxins consisting of lipids within a cell.

Why are Exotoxins Worse than Endotoxins?

Even in small quantities the exotoxins are lethal. fortunately, vaccines are available to combat them. On the other hand, endotoxins are less lethal but can cause the host to become feverish. Bacteria secrete exotoxins and release them outside the cell, whereas endotoxins are bacterial toxins located within the cells.