Oligosaccharide

An oligosaccharide (/ˌɒlɪɡoʊˈsækəˌraɪd/; from Ancient Greek (olígos) 'few' and σάκχαρ (sákkhar) 'sugar') is a type of sugar made of a small number of simple sugars. Usually, these have between three and ten sugars linked together. These molecules are important in our bodies and in plants. They help cells recognize each other and stick together, which is needed for many processes in living things.

Oligosaccharides are often found attached to other molecules like fats or proteins. When linked to proteins, they are called glycans and connect through special bonds. Some oligosaccharides attach to a specific part of a protein called asparagine, while others attach to threonine or serine. Not all oligosaccharides are part of proteins or fats; some are stored in plants or made when tiny organisms break down bigger sugar molecules like starch or cellulose. These smaller sugar pieces, such as maltodextrins or cellodextrins, help with storing and moving energy in nature.

Glycosylation

In biology, glycosylation is when a sugar molecule joins another molecule. This helps make important structures like glycoproteins and glycolipids.

N-Linked oligosaccharides connect to a part of a protein called asparagine. This happens while the protein is being made, and it can help the protein fold properly. O-Linked oligosaccharides attach to other parts of proteins, like threonine or serine. This process occurs in a cell area known as the Golgi apparatus.

Glycosylated biomolecules

Glycoproteins and glycolipids are connected to carbohydrates. They are very common on the outside of cells. They help keep cells stable and support important cell functions.

Glycoproteins have special oligosaccharide structures. These structures affect how they recognize other cells and how they resist breaking down. Glycolipids help cells recognize each other and send signals. They are made of lipids connected to oligosaccharides. They are found in the cell's outer layer and help cells interact and communicate.

Functions

All cells have special molecules on their surface called glycoproteins or glycolipids. These help us know what kind of cell it is.

Proteins called lectins can recognize small chains of sugars, called oligosaccharides, and use this to tell cells apart.

For example, blood types — like A, B, AB, and O — depend on the oligosaccharides on the surface of red blood cells. The H antigen is on everyone, but people with A blood have the A antigen too, those with B have the B antigen, those with AB have both A and B, and those with O only have H. This is why O blood is called the "universal donor". Oligosaccharides also help cells stick together, which is important when the body needs to fight infections.

Dietary oligosaccharides

Fructo-oligosaccharides (FOS) are short chains of fructose found in many vegetables. They are a type of soluble dietary fibre and can help with glucose levels in the body.

Galacto-oligosaccharides (GOS), made from galactose, are found naturally and are especially important for infants who are not breastfed.

Human milk contains oligosaccharides called human milk oligosaccharides (HMOs). These help develop good gut bacteria in infants and can protect against some viruses.

Mannan oligosaccharides (MOS) are used in animal feed to support gut health. They come from yeast cell walls and help gather harmful germs and support the immune system.