Lecture notes in Microbiology

Difference between Bacterial Endotoxin and Exotoxin – Comparison Table

Compare Exotoxin and Endotoxin

Endotoxins vs Exotoxins
(Difference between Bacterial Endotoxin and Exotoxin)

Microbial toxins are noxious substances produced by the microorganisms such as bacteria and fungi in order to promote their pathogenicity and disease-causing process. The microbial toxins usually destroy the host tissue and they facilitate the infection by disabling the host immune system. A disease that results from a specific toxin is denoted as ‘Intoxication’. A toxin is a substance that alters the normal metabolism of host cells with deleterious effects. The term ‘Toxemia’ refers to the condition caused by the toxins that have entered the bloodstream of the host.

The toxins produced by bacteria are categorized into two main categories: (1) Endotoxins and (2) Exotoxins.

More in Microbiology: Lecture Notes, PPTs, MCQs

(1). Endotoxins: They are also called as Lipopolysaccharides or LPS. LPS are present on the outer membrane of the cell wall of Gram-negative bacteria that, under certain circumstances, become toxic to specific hosts. Lipopolysaccharides are called endotoxins because they are bound to the bacterium and they are released only when the bacterial cells lyse.

Lipopolysaccharides Toxin

Continue reading

Lecture notes in Microbiology

Difference between Sterilization and Disinfection – Comparison Table

Compare sterilization and Disinfection

Sterilization vs Disinfection
(Similarities and Differences between Sterilization and Disinfection in Microbiology)

Microbes are present in almost all types of habitats. They are so ubiquitous that the presence of many microbes causes undesirable consequences such as food spoilage and diseases. Thus in many situations, it is mandatory to kill the microbes or inhibit their growth to minimize or completely nullify their destructive activities. Sterilization and Disinfection are the two commonly used methods to kill or inhibit the growth of microbes to avoid their undesirable consequences.

More in Microbiology: Lecture Notes, PPTs, MCQs

Sterilization is a process by which an article, surface or medium is freed of all living microorganisms either in vegetative or in spore state. The materials that have been subjected to the process is said to be Sterile. Usually, the sterilization process is done by physical agents such as heat, steam or radiation.

Disinfection is the use of chemical agents that destroy pathogenic microorganisms. Disinfection reduces the number of microbes to a minimal level so that it is no longer harmful. Disinfection destroys only vegetative cells, not the spores (endospores and fungal spores)

The present post discusses the Similarities and Differences between Sterilization and Disinfection with a Comparison Table.

Continue reading

biological chemistry

Disaccharides: Properties, Structure, Formation and Examples (Short Lecture Notes)

Disaccharides Lecture Notes

(Carbohydrates Part 3: Properties, Structure and Examples of Disaccharides)

What are Disaccharides?

Disaccharides are carbohydrates which contain two covalently linked monosaccharide units. Sucrose, Maltose, Lactose, Trehalose and Cellobiose are naturally occurring disaccharides. The individual monosaccharide units in a disaccharide are called ‘residues’. All disaccharides are soluble in water

Glycosidic bonds links monosaccharide units

The monosaccharide units in disaccharides (and also in polysaccharides) are linked through a special type of covalent bond called Glycosidic bond (specifically O-glycosidic bond). O-glycosidic bond is formed by the reaction between the hydroxyl group of one monosaccharide with the anomeric carbon atom of the other. During the glycosidic bond formation, one molecule of water is eliminated as given in the diagram. Glycosidic bonds are strong covalent bonds and they can be hydrolyzed by treating with mild acids. The hydrolysis of the glycosidic bond of a disaccharide releases its corresponding monosaccharide units.

Structure of Glycosidic Bond

Continue reading

biological chemistry

Monosaccharides: Definition, Structure, Characteristics, Classification, Examples and Functions

Biochemistry of Monosaccharides

Chemical Structure, Characteristics, Examples & Classification

Monosaccharides are Simplest Sugars

Monosaccharides are the simplest carbohydrates. They are polyhydroxy aldehydes or ketones with a carbon backbone. The carbon backbone in monosaccharides usually consists of 3 – 6 carbon atoms. The simplest monosaccharides are glyceraldehyde and dihydroxyacetone (with 3 carbons). The most abundant monosaccharide in nature is a 6 carbon sugar called glucose. Majority of the monosaccharides follow the empirical formula C(H2O)n. Monosaccharide with five or more carbon can predominantly exist as cyclic structures in the aqueous condition. All monosaccharides are colourless, crystalline solids and that are readily soluble in water but insoluble in nonpolar solvents. Most of the monosaccharides are sweet in taste.

More in Biochemistry: Lecture Notes, MCQ, PPTs, Videos

Polyhydroxy aldehydes

Chemical Structure of Monosaccharides

Ø  All monosaccharides are polyhydroxy (contain many hydroxyl groups) aldehydes or ketones.

Ø  The hydroxyl groups are attached to the carbon backbone.

Ø  The number of carbon atoms in the backbone of monosaccharides varies from 3 to 6.

Ø  The carbon backbone of monosaccharides is unbranched and individual carbon atoms are connected by single bonds.

Ø  Monosaccharides are broadly classified into Aldoses and Ketoses.

Ø  In the open chain conformation of a monosaccharide, one of the carbon atoms of the backbone is double bonded to an oxygen atom to form the carbonyl group (C=O).

Ø  If the carbonyl group is at the end of the carbon chain it will be an aldehyde group (R – COH) and thus the sugar formed will be an Aldose sugar.

Ø  Similarly, if the carbonyl group is inner to the carbon chain, it will be a keto group (C=O) and the sugar formed will be a Ketose sugar.

Continue reading

Lecture notes in Microbiology

Difference between the Cell Wall of Gram Positive and Gram Negative Bacteria

Compare Cell wall Gram Positive and negative

Difference between the Cell Wall of Gram Positive and Gram Negative Bacteria

Most of the bacterial cells are surrounded by a thick rigid cell wall. The cell wall provides shape to the cell and protects the bacteria from changes in the osmotic pressure. Peptidoglycan (murein) is the principal component of the bacterial cell wall and it is responsible for the shape and extreme tough nature of the cell wall.

Based on the characteristics of the cell wall, the bacterial cells are classified into Gram Positive and Gram Negative, primarily based on the classical staining reaction called Gram Staining. In the previous post we have discussed about the Similarities and Differences between Gram Positive and Gram Negative Bacteria. Both Gram positive and Gram negative bacterial possess cell wall, however, their structural organization, chemical and physical properties varies. In general, the cell wall of Gram positive bacteria has simpler chemical structures compared to the Gram negative bacteria. The present post discusses the Differences between the Cell Wall of Gram positive and Gram negative bacteria with a comparison table.

OSC Microbio 03 03 CellWalls

Comparison of the Cell Wall of Gram Positive and Gram Negative Bacteria

Continue reading