What are lipids?

Lipids are a class of non-polar organic solvents that are insoluble in water but easily soluble in fatty solvents. and important organic compounds that can be utilized by the body. Lipids include a wide range of lipids, and there are many ways to classify them. It is usually divided into simple lipids, complex lipids, and derived lipids according to the main components of lipids, excluding saponified lipids. Lipids include a wide variety of molecules that are characterized primarily by two elements, carbon and hydrogen, in non-polar covalent bonds.

Lipids include fats, phospholipids, and sterols, among others. The elements contained in lipids are carbon, hydrogen and oxygen, while some lipids also contain nitrogen and phosphorus. For example, phospholipids contain phosphorus, vitamin D contains nitrogen, and fat only contains three elements: carbon, hydrogen, and oxygen. The basic unit of fat is glycerol, fatty acid, phospholipid is the main component of cell membrane, sterols include cholesterol, sex hormone, vitamin D and so on.

Lipids include phospholipids, glycolipids, and cholesterol and cholesterol esters.

①Phospholipids are lipids containing phosphoric acid, including phosphoglycerides composed of glycerol and sphingomyelin composed of sphingosine. In animal brains and eggs, soybean seeds contain more phospholipids. Read more: What Are Phospholipids?
②Glycolipids are lipids containing sugar groups.
③ Also, substances such as cholesterol and steroids (steroids) mainly include cholesterol, bile acid, sex hormones and vitamin D. These substances play an important regulatory role for the organism to maintain normal metabolism and reproductive processes.

In addition, cholesterol is also the raw material for the synthesis of fatty acid salts, vitamin D3 and steroid hormones, etc. It can regulate the absorption of lipid substances in the body, especially the absorption of fat-soluble vitamins (A, D, E, K) and the metabolism of calcium and phosphorus. These three lipids are important components of biofilms, forming a hydrophobic “barrier” that separates the water-soluble components of cells and divides cells into small compartments such as organelles/nuclei to ensure simultaneous intracellular multiplexing. Various metabolic activities do not interfere with each other and maintain the normal structure and function of cells.


Phospholipids are an important component of biological membranes, which are characterized by the formation of mixtures containing fatty acids and phosphoric acid after hydrolysis. According to the main chain structure of phospholipids, it is divided into phosphoglycerol trans and sphingomyelin. Read more: what are phospholipids
1. The main chain of phosphoglycerides is glycerol-3-phosphate, the other two hydroxyl groups in the glycerol molecule are esterified by fatty acids, and the phosphate group can be esterified by various small molecular compounds with different structures to form various Phosphoglycerides. The most abundant in the body are phosphatidylcholine (lecithin), phosphatidylethanolamine (cephalin), phosphatidylserine, phosphatidylglycerol, diphosphatidylglycerol (cardiophosphatide) and phosphatidyl inositol, etc. There are several types of phospholipids depending on the fatty acid composition.

It can be known from the molecular structure that the central atom of the glycerol molecule is asymmetric. Therefore, there are different three-dimensional configurations. The naturally occurring phosphoglycerides all have the same host chemical configuration. Follow chemical conventions. These molecules can be represented by two-dimensional projections. The configurations of D- and L glyceraldehyde were determined based on their X-ray crystallography results. Right-handed is the D configuration, and left-handed is the L configuration. The stereochemical configuration and nomenclature of glycerol phosphates are thus determined.

2. Sphingomyelin (sphingomyelin) Sphingomyelin is a phospholipid containing sphingosine or dihydrosphingosine, its molecule does not contain glycerol, and is a molecule of fatty acid linked to the amino group of sphingosine by an amide bond. Sphingosine or dihydrosphingosine is an amino diol with a long aliphatic chain. It has a hydrophobic long-chain aliphatic hydrocarbon tail and a polar head with two hydroxyl groups and one amino group.

Sphingomyelin contains phosphoric acid, and its terminal hydroxyl group is phosphocholine ethanolamine. The most abundant sphingomyelin in the human body is sphingomyelin, which is composed of sphingosine, fatty acid and phosphorylcholine. Sphingomyelin is an important phospholipid constituting biofilms. It often coexists with lecithin on the outside of the cell membrane.

Lipid PEG

Polyethylene glycol (PEG) lipid linkers are PEG derivatives containing lipid molecules such as DSPE, which have been used extensively to improve circulation times for liposome-encapsulated drugs.
Lipid PEG reagents are used in bioconjugation, drug formulation, and nanoparticle delivery.
AxisPharm now offers an extensive group of PEG-lipid linkers incorporating various functionalized PEG termini, like Amine, Carboxylic acid, Azide PEG, Aldehyde, Thiol, and Hydroxy.