Difference Between Glycerophospholipids and Sphingolipids

Key Difference – Glycerophospholipids vs Sphingolipids
 

Glycerophospholipids and sphingolipids are important constituents of the cell membrane. The glycerophospholipids contain a three carbon glycerol backbone while the sphingolipids contain organic aliphatic amino alcohol sphingosine. This is the key difference between glycerophospholipids and sphingolipids. Both are important constituents of the cell membrane that have similar properties.

Cell membranes are considered as important structures for a cell since they involve in numerous functions during different cellular activities. They involve in the regulation of exchange of materials between the cell and the outer environment and also function in cell signalling processes that enable cells to communicate with the surrounding cells. The cell membranes are made up of different important materials.

CONTENTS

1. Overview and Key Difference
2. What are Glycerophospholipids
3. What are Sphingolipids
4. Similarities Between Glycerophospholipids and Sphingolipids
5. Side by Side Comparison – Glycerophospholipids vs Sphingolipids in Tabular Form
6. Summary

What are Glycerophospholipids?

Glycerophospholipds are considered as the main constituents of membrane bi layer or the lipid bilayer. They are also termed as phosphoglycerides.  Glycerophospholipds consist of three major constituent groups within the molecule itself. They are three carbon glycerol back bone, two long chains on fatty acids that are esterified to first and the second carbon atoms (C1 and C2 carbons) of the glycerol backbone and phosphoric acid that is esterified into the final carbon atom; carbon 3 (C3) hydroxyl group of glycerol.

Most glycerophospholipds possess an alcohol head that is esterified to the phosphate. Glycerophospholipds and fatty acids are considered as amphiphilic molecules since they have both hydrophilic and hydrophobic parts. The aliphatic chains of fatty acids are considered hydrophobic. Fatty acids’ carboxyl groups and the head groups of glycerophospholipds are considered as hydrophilic. The hydrophobic nature of glycerophospholipds drives this molecule in the assembling of lipid bilayers.

The cells in the body synthesize different types of major glycerophospholipds with the utilization of different fatty acids and through esterification of one of five different alcohols to the phosphate group.  In a general glycerophospholipid, the first carbon contains either one double bond or no double bonds and the second carbon possesses two or more double bonds. These double bonds create a permanent bend in the hydrocarbon chain. This permanent bend provides the necessary fluidity to the bilayer.

Various alcohol head groups that are present in glycerophospholipds contribute to the classification of glycerophospholipds accordingly. If no head groups are present, glycerophospholipds are referred to as phosphatidic acid, and if a glycerol head is present it is termed as phosphatidylglycerol and if a choline head group is present it is referred to as phophatidylcholine.

What are Sphingolipids?

A type of lipids that associate the cell membranes are referred to as sphingolipids. They are based on an eighteen carbon amine alcohol. In simple terms, sphingolipids contain organic aliphatic amino alcohol sphingosine or any substance that resembles the sphingosine. All the members that belong to the group sphingolipids contain a complex or simple sugar that is attached to the first carbon of the alcohol group (C1). The member that deviates from this common structure is sphingomyelin. This molecule consists of  a phosphorylcholine group that is the same polar head group present in phosphatidylcholine.

Since sphingomyelin does not contain the sugar moiety, it is considered as an analog to phosphatidylcholine. In addition to the sugar, all sphingolipids contain a fatty acid, which is attached to the amino group of the sphingosine molecule. The sphingomyelin is the only sphingolipid that is considered as a phospholipid that functions as a major component of biological membranes.

The sphingomyelin is the only phosphorous containing sphingolipids that are present in abundant forms in the nervous tissue. Sphingomyelins also present in the blood.  Sphingolipidosis and sphingolipodystrophy are two disease conditions that are developed due to abnormal sphingolipid metabolism. Due to the accumulation of sphingolipids in the brain, there can be a development of a rare disease called Tay Sachs disease condition.

What are the Similarities Between Glycerophospholipids and Sphingolipids?

• Both Glycerophospholipids and Sphingolipids are constituents of cell membranes.
• Both contain fatty acids.
• Both are distributed asymmetrically in the lipid bilayer.
• Both Glycerophospholipids and Sphingolipids are amphipathic.

What is the Difference Between Glycerophospholipids and Sphingolipids?

Summary – Glycerophospholipids vs Sphingolipids

Cell membranes are important structures that separate the internal cell environment from the external environment. They are made up of different constituents such as Glycerophospholipids and Sphingolipids. Glycerophospholipds are considered as the main constituents of the lipid bilayer. Most glycerophospholipds possess an alcohol head that is esterified to the phosphate. Sphingolipids are another class of lipids that associate the membranes. All the members that belong to the group sphingolipids contain a complex or simple sugar that is attached to the alcohol on the first carbon except sphingomyelin. Both contain fatty acids in their structure. This is the difference between Glycerophospholipids and Sphingolipids.

Reference:

1.Rodriguez-Cuenca, S., et al. “Sphingolipids and Glycerophospholipids – The ‘Ying and Yang’ of Lipotoxicity in Metabolic Diseases.” Progress in Lipid Research, vol. 66, 2017, pp. 14–29., doi:10.1016/j.plipres.2017.01.002
2.Britannica, The Editors of Encyclopaedia. “Sphingolipid.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 22 Apr. 2016. Available here 
3.Farooqui, Akhlaq A. “Glycerophospholipids.” ELS, 2014, doi:10.1002/9780470015902.a0000726.pub3.

Image Courtesy:

1.’Glycerophospholipids’By Alnokta – Own work, (Public Domain) via Commons Wikimedia  
2.’Sphingolipids general structures’By LHcheM – Own work, (CC BY-SA 3.0) via Commons Wikimedia