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What Are the Functions of Glycoproteins?

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Glycoproteins are a form of protein that contain sugar residue. Glycoproteins are usually found at the surface of cells and assist with important processes in the body.

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What Are the Functions of Glycoproteins?
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Glycoproteins are a form of protein that contains sugar residue. The different characteristics of sugar may change so that it attaches itself to a characteristic of the protein. Glycoproteins depend on sugar to function properly. Sugar helps them reach their destination in the organism of the cell. They play an important role in the body at the cell level. Glycoproteins are usually found at the surface of cells. Here, they work as membrane proteins sometimes facilitating some of the body's important processes like reproduction. There are three different types of glycoproteins that are determined differentiated through their synthesis mechanism and structure. These glycoproteins are either N-linked, O-linked or non-enzymatic glycoproteins.

Understanding How Glycoproteins Work in the Body
Glycoproteins aid in the development of tissue function when they adhere to the cells found in the body. Glycoproteins are found in connective tissues, cell walls and blood plasma. Depending on where they are located in the body, they will display structural differences. Glycoproteins play a major role in reproduction since they are located on the surface of sperm. Glycoproteins change the plasma membrane permeability making it easier for the attraction of eggs to the sperm cells.

N-linked Glycoproteins
These types of glycoproteins are modified and synthesized inside the membrane organelles of a cell. The protein part of the glycoprotein is created on the surface by other amino acids. This creates a linear polymer chain of amino acids called a polypeptide. At least 20 different types of amino acids are used to create polypeptides. The order of the amino acids in the polypeptide chain is crucial to its function. This order is called the amino acid sequence. The import of this is found when one considers that if the amino acids were ordered in a different sequence, they would not have the same function.

Some of these N-linked glycoproteins contain carbohydrates. Carbohydrates do not attach themselves to polypeptides one at a time. Instead, carbohydrates that contain many different types of sugar residues attach to the translated protein. The carbohydrates that are inside the glycoprotein are modified by enzymes that also takes away some of the sugars. It then attaches other sugars so that it forms new glycoproteins.

O-linked Glycoproteins
These types of glycoproteins are created by adding sugar to the hydroxyl chain and polypeptides. They are different from the N-linked glycoproteins because they are made by the addition of sugar one type at a time. O-Linked glycoproteins often become part of an extracellular matrix after it is secreted by the cell. This extracellular matrix surrounds the O-linked glycoproteins.

Non-enzymatic Glycoproteins
This creates glycoproteins when sugar is added to polypeptides in a process called glycosylation. The concentration of sugar and time control glycosylation. People, who have higher amounts of circulating glucose, experience higher levels of glycosylation. Additionally, older proteins also have a higher incidence of glycosylation. This is the primary basis of the glycosylated hemoglobin diagnostic test that is used for checking on the blood sugar levels for diabetics. It is also used for their long-term maintenance and monitoring.

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