GLUCOCALIX: CHARACTERISTICS AND FUNCTIONS - BIOLOGY - 2024

The glycocalyx is a carbohydrate - enriched layer covering the outside of various types of cells, particularly bacteria and human cells. This protective coating fulfills several very important functions for the cell.

Basically, the glycocalyx is made up of chains of polysaccharides (sugars) attached to various protein and lipid molecules, thus forming associations called glycoproteins and glycolipids, respectively. The result is a sticky, fibrous web with the ability to hydrate.

In eukaryotic cells, the composition of the glycocalyx can be a factor used for the recognition of the cell.

For its part, in bacterial cells, the glycocalyx provides a protective layer against host factors, in fact, the possession of a glycocalyx is associated with the ability of bacteria to establish an infection.

In humans, glycocalyx is found on the membranes of vascular endothelial cells and epithelial cells of the digestive tract.

For its part, the bacterial glycocalyx can surround individual cells or colonies, thus forming the so-called bacterial biofilms.

Glucocalyx in bacteria

The structural characteristics and chemical composition of the bacterial glycocalyx differ by species, but in general this additional coating can come in one of two forms:

Slimes

A glycocalyx is considered a slime layer when glycoprotein molecules loosely associate with the cell wall.

However, bacteria that are coated with this type of glycocalyx are protected against dehydration and loss of nutrients.

Capsules

The glycocalyx is considered a capsule when the polysaccharides are more firmly attached to the cell wall.

The capsules have a sticky consistency which, in addition to protection, also facilitates adhesion to solid surfaces in the environment.

Bacteria that have capsules are considered encapsulated, and generally have a higher pathogenicity (ability to cause disease), because capsules protect bacteria, including from phagocytic white blood cells of the immune system.

Glucocalyx in humans

In humans, glucocalyx is very important for vascular function and for the digestive system.

Glucocalyx in the vascular endothelium

Blood vessels are actually small tubes made of cells. The cells inside the tube are called endothelial cells and they must withstand the pressure of the blood that constantly flows over them.

To resist this, the vascular endothelial cells produce a mucilaginous layer. This glycocalyx also has enzymes and proteins that help cells involved in blood clotting to adhere to blood vessels when necessary.

The main function of the glucocalyx in the vascular system is to maintain endothelial homeostasis.

The alteration of the structure of the glycocalyx in the vascular endothelium could cause the formation of a blood clot within a blood vessel, obstructing the flow of blood through the circulatory system and thus have detrimental effects on health.

Glucocalyx in the digestive tract

The second best described example of glucocalyx in humans is found in the digestive system. The small intestine is responsible for absorbing all the nutrients that come from the food we eat.

The cells in the small intestine responsible for absorbing nutrients have many small folds called microvilli.

Each of the cells that make up the microvilli is covered with glycocalyx, which is made up of mucopolysaccharides (long chains of complex sugars) and glycoproteins.

Thus, it provides an additional surface for absorption and also includes enzymes secreted by these cells that are essential for the final steps of digestion of food.

Every time we eat there is a risk of ingesting harmful material that can cross the intestinal lining.

Therefore, in addition to the function of digestion and absorption of nutrients, the glucocalyx of the intestinal epithelium must also fulfill the function of a protective barrier to filter harmful products.

Other functions of the glycocalyx

Glycocalyx also fulfills other functions in defense against infections and cancer, cell adhesion, regulation of inflammation, fertilization, and embryonic development.

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