What is the Difference Between Glycolipid and Glycoprotein

The main difference between glycolipid and glycoprotein is that glycolipid is a carbohydrate-attached lipid whereas a glycoprotein is a carbohydrate-attached protein. Furthermore, glycolipids serve as cell markers or antigens recognized by the immune system as self or non-self while glycoproteins serve as receptors for chemical signals and play a role in cell adhesion.

Glycolipid and glycoprotein are two types of molecules mainly found in the cell membrane. They perform a number of important functions in the cell.

Key Areas Covered

1. What is a Glycolipid
     – Definition, Structure, Role
2. What is a Glycoprotein
     – Definition, Structure, Role
3. What are the Similarities Between Glycolipid and Glycoprotein
     – Outline of Common Features
4. What is the Difference Between Glycolipid and Glycoprotein
     – Comparison of Key Differences

Key Terms

Antigens, Carbohydrates, Cell Attachment, Cell Adhesion, Glycolipid, Glycoprotein, Receptors

What is a Glycolipid

A glycolipid is a lipid molecule attached to a short chain of carbohydrates. Glycolipids occur on the cell membrane of eukaryotes and the sugar residue of the glycolipid molecule extends out from the phospholipid bilayer. The main function of glycolipids is to stabilize the cell membrane by making hydrogen bonds with surrounding water molecules. In addition, they involve in cellular recognition, which is important in triggering an immune response. Also, glycolipids play a key role in cell attachment during the formation of tissue.

Figure 1: Glycolipid

Furthermore, the two main types of lipids on the cell membrane are sphingolipids and glycolipids. The backbone of glycolipids is made up of glycerol. Also, the four main blood types of humans known as A, B, AB, and O are classified based on the type of oligosaccharide attached to a specific glycolipid on the cell membrane of red blood cells.

What is a Glycoprotein

A glycoprotein is a protein molecule attached to a short chain of carbohydrates. Generally, glycoproteins are produced as cotranslational or posttranslational modifications in a process known as glycosylation. Commonly, the secreted extracellular proteins undergo glycosylation. However, glycoproteins mainly serve as integral membrane proteins, which play a key role in cell-cell interactions. Also, they serve as receptors for chemical signals.

Figure 2: Glycolipids and Glycoproteins on the Cell Membrane

Moreover, glycoproteins are a more diverse group of molecules than glycolipids. Some examples of glycoproteins are collagen, a structural molecule, mucins that are lubricants, transport molecules such as transferrin, immunologic molecules such as immunoglobulins and histocompatibility antigens, hormones such as HCG and TSH, etc.

Similarities Between Glycolipid and Glycoprotein

• Glycolipid and glycoprotein are two types of molecules mainly found on the cell membrane.
• They are either lipids or protein molecules bound to short carbohydrate chains such as glucose, galactose, lactose, fructose, sialic acid, N-acetyl glucosamine, etc.
• Further, the carbohydrate chains protrude out from the cell surface.
• Also, they stabilize the membrane structure by forming hydrogen bonds with the surrounding water molecules.
• Generally, they serve as receptor molecules which bind to the hormones and neurotransmitters, initiating various signaling pathways in the cell.
• Besides, they play a role in cell attachment and cell recognition.

Difference Between Glycolipid and Glycoprotein

Definition

Glycolipid refers to lipids with a carbohydrate attached by a glycosidic (covalent) bond while glycoprotein refers to any of a class of proteins which have carbohydrate groups attached to the polypeptide chain. Thus, this is the main difference between glycolipids and glycoproteins.

Occurrence

Glycolipids mainly occur on the cell membrane while glycoproteins occur on the cell membrane and in the blood.

Diversity

Moreover, diversity is another difference between glycolipids and glycoproteins. Glycolipids are less diverse while glycoproteins are more diverse.

Main Function

Functionally, glycolipids facilitate cellular recognition while glycoproteins serve as receptors for chemical signals. Hence, this is the functional difference between glycolipids and glycoproteins.

Conclusion

Glycolipid is a lipid molecule with attached short chains of carbohydrates. Glycolipids mainly occur on the cell membrane. Their main function is to involve in cell recognition. In comparison, glycoproteins are protein molecules attached to the short chains of carbohydrates. They occur on the cell membrane as well as in the blood. The main function of glycoproteins is to serve as antigens. Thus, the main difference between glycolipids and glycoproteins is the type of molecules, occurrence, and function.

References:

1. Corsini, Dominic. “Glycolipids: Definition, Function & Structure.” Study.com, Study.com, Available Here.
2. Robb, Amanda. “What Are Glycoproteins? – Definition, Functions & Examples” Study.com, Available Here.

Image Courtesy:

1. “Glycolipid” By Wpcrosson – Own work (CC BY-SA 4.0) via Commons Wikimedia  
2. “Cell membrane detailed diagram edit2” By Original: Cell_membrane_detailed_diagram.svg: LadyofHats Mariana Ruizderivative work: Alokprasad84 – original svg Mariana Ruiz edited by Alokprasad84 (CC BY-SA 3.0) via Commons Wikimedia