The key difference between lecithin and sphingomyelin is that lecithin has a glycerol group, while sphingomyelin does not have a glycerol group.
Phospholipids are lipids containing phosphoric acid in their structure. In phospholipids, the two hydroxyl groups of glycerol are esterified with phosphoric acid. These lipids serve as the structural components of biological membranes. However, some phospholipids do not have a glycerol group. Moreover, phospholipids are further subdivided into three subgroups: phosphoglycerides (lecithin), phosphoinositides (phosphatidyl inositol), and phosphospingosides (sphingomyelin). Therefore, lecithin and sphingomyelin are two different types of phospholipids.
CONTENTS
1. Overview and Key Difference
2. What is Lecithin
3. What is Sphingomyelin
4. Similarities – Lecithin and Sphingomyelin
5. Lecithin vs Sphingomyelin in Tabular Form
6. Summary – Lecithin vs Sphingomyelin
What is Lecithin?
Lecithin is a phospholipid. It is also a type of phosphoglyceride. Chemically, lecithin is called phosphotidylcholine. This is because lecithin contains a choline group. Upon hydrolysis, lecithin yields glycerol, fatty acid, phosphoric acid, and choline. Lecithin was first isolated in 1845 by a French chemist and pharmacist called Théodore Goble. Moreover, lecithin is a yellow-brownish fatty substance that generally occurs in animal and plant tissues. In addition, lecithin is also amphiphilic in nature. It means lecithin can attract both water and fatty substances. Biologically, lecithin is present in various biological materials, including venous blood, human lungs, bile, brains of animals such as humans, sheep, and chickens.
Figure 01: Lecithin
Lecithin can be extracted chemically from hexane, ethanol, acetone, petroleum ether, and benzene. It can also be extracted mechanically. The sources for lecithin include egg yolk, marine foods, soybeans, milk, rapeseeds, cottonseeds, and sunflower oil. Lecithin has various functions. Normally, it can be used as an emulsifier and surfactant. Furthermore, in the food industry, it is used as a food additive and dietary supplement. The other applications include the pharmaceutical industry (wetting agent and stabilizing agent), animal feed, paint industry (rust inhibitor and colour intensifying agent), release agent for plastic, and antioxidant in textile, rubber, and other industries. Lecithin is associated with a well-known disease called Lecithin cholesterol acyltransferase deficiency disease.
What is Sphingomyelin?
Sphingomyelin is a phospholipid. It is categorized under phosphospingosides. Sphingomyelin though it is a lipid, it does not have a glycerol group. Upon hydrolysis, it yields fatty acid, sphingosine (unsaturated amino alcohol), phosphoric acid, and choline. Sphingomyelin is present in the cell membrane of animal cells, especially in the myelin sheath (surrounds the nerve axon) of neurons. In humans, 85% of phosphospingosides are sphingomyelins. Moreover, sphingomyelin typically makes up 10-20% of the plasma membrane of the lipids. Sphingomyelin was first isolated in 1880 by German chemist Johann L.W Thudicum. In most tissues of mammals, sphingomyelin content ranges from 2 to 15%. Mainly, sphingomyelins are found in nerve tissues, red blood cells, and ocular lenses.
Figure 02: Sphingomyelin
Sphingomyelin is a plasma membrane component, and it participates in many signalling pathways. The sources for sphingomyelin include vegetables, soybean, corn, wheat, peanuts, etc. Industrially, sphingomyelin and its metabolites have a wide range of applications in the food, cosmetic, and pharmaceutical industries. Furthermore, excessive accumulation of sphingomyelin in the brain leads to a syndrome called Niemann- pick disease.
What are the Similarities Between Lecithin and Sphingomyelin?
- Lecithin and sphingomyelin are two different types of phospholipids.
- Both compounds can be found in biological membranes.
- They contain a choline group.
- Both compounds have biological functions as well as industrial uses.
- Their deficiencies and accumulations are associated with different diseases.
What is the Difference Between Lecithin and Sphingomyelin?
Lecithin is a phospholipid that has a glycerol group, while sphingomyelin is a phospholipid that does not have a glycerol group. Thus, this is the key difference between lecithin and sphingomyelin. Furthermore, lecithin was first isolated in 1845 by a French chemist and pharmacist called Théodore Goble. On the other hand, sphingomyelin was first isolated in 1880 by German chemist Johann L.W Thudicum.
The below infographic presents the differences between lecithin and sphingomyelin in tabular form for side-by-side comparison.
Summary – Lecithin vs Sphingomyelin
Phospholipids are lipids containing phosphoric acid in their structure. Lecithin and sphingomyelin are two different types of phospholipids. Both these compounds are very important structural components in the biological membrane. Lecithin is a phospholipid that has a glycerol group, while sphingomyelin is a phospholipid that does not have a glycerol group. So, this is the key difference between lecithin and sphingomyelin.
Reference:
1. Christiansen, Sherry. “What Is Lecithin?” Verywell Health.
2. “Sphingomyelin.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Lecithine-palmitin-ölsäure” By Roland.chem – own made (CC BY-SA 3.0) via Commons Wikimedia
2. “Sphingomyelin Synthesis” By Taylochr – Own work (CC BY-SA 3.0) via Commons Wikimedia
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