What is a Lipid?

Lipids are compounds that are insoluble in water and can be extracted by non-polar organic solvents such as ether, chloroform, and benzene. They mainly include esters and their derivatives generated by the interaction of fatty acids and alcohols. They are also commonly called fats and oils. Lipids are polymers of fatty acids containing long nonpolar hydrocarbon chains and small polar regions containing oxygen. Lipids play many important roles in the human body, including as a source of energy, forming the structure of cell membranes, as signaling molecules, and as insulators that protect internal organs. In addition, lipids are also raw materials for various pharmaceutical and chemical industries.


Lipids are a type of organic small molecule substances in the body, which cover a wide range, have greatly different chemical structures, and have different physiological functions. The common physical property of lipids is that they are insoluble in water but soluble in organic solvents, and can aggregate with each other in water to form internal hydrophobic aggregates. There are three main directions for understanding lipids:

Lipids in food: The fields of medicine, nutrition, sports and health are more concerned, mainly considering the relationship between diet and human/animal diseases. Generally, those that are liquid at room temperature are called oils, while those that are solid at room temperature are called fats.

Lipids in the human body/animals and plants: Physiology and pathology focus on studying the role of lipids in their physiological/pathological states. Lipids are also components of human cell tissues, such as cell membranes and nerve myelin sheaths.

Lipid compounds and their derivatives: In recent years, researchers have begun to explore the application of lipids in drug development and chemical production, including drug delivery, pharmaceutical preparations, specialty chemical manufacturing, cosmetics development, etc.

Lipid Types


Grease is triglyceride or triacylglycerol, which is the collective name for oil and fat. Fat is synthesized from the dehydration of glycerol and fatty acids. The -OH in the carboxyl group of the fatty acid combines with the -H in the hydroxyl group of the glycerol and loses a molecule of water, so an ester bond is formed between the glycerol and the fatty acid and becomes a fat molecule. The three acyl groups in fats (the remaining atomic groups after removing hydroxyl groups from inorganic or organic oxygen-containing acids) are generally different and originate from C16, C18 or other fatty acids. Fatty acids with double bonds are called unsaturated fatty acids, and those without double bonds are called saturated fatty acids.

Oils and fats are widely distributed. There is a certain amount of oils in the seeds of various plants and the tissues and organs of animals. In particular, the seeds of oil crops and the adipose tissue under the skin of animals are rich in oils. Fat in the human body accounts for about 10% to 20% of body weight. There are many types of fatty acids in the human body, and they can be arranged and combined in different ways when producing triglycerides. Therefore, triglycerides exist in many forms.


Lipoids include three major categories: phospholipids, glycolipids, and cholesterol and cholesterol esters. Phospholipids are lipids containing phosphoric acid, including glycerophospholipids composed of glycerol and sphingomyelin composed of sphingosine. In animal brains and eggs, soybean seeds contain more phospholipids. Glycolipids are lipids containing sugar groups. In addition, substances such as cholesterol and steroids mainly include cholesterol, bile acid, sex hormones, vitamin D, etc. These substances play an important regulatory role in maintaining normal metabolism and reproductive processes of organisms.

In addition, cholesterol is also a synthetic raw material for fatty acid salts, vitamin D3 and steroid hormones. It plays an important role in regulating the absorption of lipids, especially the absorption of fat-soluble vitamins (A, D, E, K) and calcium and phosphorus metabolism. These three major types of lipids are important components of biological membranes, forming a hydrophobic barrier that separates water-soluble components of cells and divides cells into small compartments such as organelles/nuclei, ensuring that multiple processes occur simultaneously within the cell. A variety of metabolic activities without interfering with each other, maintaining the normal structure and function of cells, etc.

What is a Lipid Made of?

Simple Lipids

A compound formed by the dehydration condensation of fatty acids and alcohols.

  • Wax: They are water-insoluble solids that are esters of higher fatty acids and long-chain monohydroxy fatty alcohols, or esters of higher fatty acid sterols. Common ones include real wax, sterol wax, etc. Real wax is a type of fatty acid ester of long-chain monohydric alcohol. Solid ester wax is an ester formed from sterols and fatty acids, such as vitamin A ester, vitamin D ester, etc.

Complex Lipids

Complex lipids are fatty acid esters containing other chemical groups. The body mainly contains two complex lipids, phospholipids and glycolipids.

  • Phospholipids: Glycerophospholipids (lecithin, cephalin), sphingomyelin (abundant in nerve cells).
  • Glycerolipids: Higher fatty acids and glycerin, the most abundant lipids.

Lipid Precursors and Derivatives

Fatty acids and their derivatives prostaglandins, etc. Long-chain fatty alcohols, such as cetyl alcohol, etc.

  • Terpenes and steroids and their derivatives: Do not contain fatty acids and are all derivatives of isoprene.
  • Derived lipids: Hydrolyzates of the above lipids, including fatty acids and their derivatives, glycerin, sphingosine, etc. Higher fatty acids, glycerol, sterols, prostaglandins.

Conjugated Lipids

A complex formed between lipids and other biomolecules. Such as glycolipids, lipoproteins, etc.

  • Glycolipids: Compounds in which sugars and lipids are linked by glycosidic bonds (covalent bonds), such as cholera toxin.
  • Lipoproteins: Products formed by non-covalent combination of lipids and proteins in the liver, such as several lipoproteins in the blood.

Lipid Structure

Lipids cover a wide range, and there are many ways to classify them. Lipids are usually classified according to their main components: simple lipids, complex lipids, derived lipids, and unsaponifiable lipids. Lipids include a variety of molecules, which are characterized by being mainly composed of two elements, carbon and hydrogen, with non-polar covalent bonds. Since these molecules are non-polar, they are incompatible with water and are therefore hydrophobic. Strictly speaking, lipids are not macromolecules because their relative molecular masses are not as large as those of sugars, proteins, and nucleic acids, and they are not polymers.

Diagram of a lipid bilayerFig. 1. Diagram of a lipid bilayer.

Lipid Function

Molecules in lipids not only provide structure to the cell membrane, but also store energy and play an important role in cell signaling and functional regulation. Defects in lipid metabolism can cause a variety of inherited metabolic diseases. Typically, the accumulation of abnormal lipids in the blood and tissues that damage cells lead to disorders of lipid metabolism. Accurate identification of abnormal lipids is the key to effective diagnosis and treatment. Additionally, lipids can be used as drug delivery systems, drug targets, or even as therapeutic agents themselves.

Lipids for Cellular Energy Storage

Lipids are the best form of energy storage. For example, triglycerides are an important source of energy for the body. Each gram of triglycerides contains 9 kcal. Excess calories from carbohydrates, proteins, fats and alcohol are converted into fatty acids (triglycerides) and stored in the body. Triglycerides can also assist in the digestion, absorption and transport of vitamins. Fat-soluble vitamins (vitamins A, D, E, K) can only be digested and absorbed by the body when combined with fat.

Lipids for Biomembrane Scaffolds

Liquid mosaic model of cell membrane: phospholipid diester layer, cholesterol, proteins, glycolipids, glycerophospholipids and sphingomyelin. Among them, phospholipids are not only the main component of cell membranes, but also an important emulsifier. The digestion and transport of fat must be carried out smoothly with the participation of emulsifiers. Additionally, some research suggests that lecithin may help prevent Alzheimer's disease and lower blood cholesterol levels.

Lipids for Biological Signaling

Lipids are also precursors of hormones, vitamins and pigments (terpenes, sterols). For example, cholesterol is the most important animal sterol, which can synthesize steroid hormones (sex steroids and corticosteroids) and vitamin D; it can also synthesize bile, which is an important emulsifier in the human body.

Lipid for Drug Delivery

Lipid-based drug delivery systems have several advantages over other drug delivery systems. For example, they are biocompatible, biodegradable, and protect the drug from degradation and clearance by the body's immune system. Lipid-based drug delivery systems can also improve the solubility and bioavailability of insoluble drugs and can increase the circulation time of drugs in the body. Lipids can be used to formulate drug molecules into lipid nanoparticles, liposomes, micelles, or solid lipid nanoparticles, thereby enhancing drug solubility, stability, and targeting to specific tissues or cells. For example, lipid nanoparticles consisting of lipid bilayers surrounded by lipid cores have been shown to improve the oral bioavailability of poorly water-soluble drugs by protecting them from degradation in the gastrointestinal tract and enhancing their absorption in the blood.

Lipids for Drug Targets

Lipid compounds may also serve as drug targets for the development of novel therapeutic agents. Lipids are involved in various cellular processes, including cell signaling, inflammation, and metabolism, and dysregulation of lipid metabolism has been implicated in the pathogenesis of many diseases, such as cancer, cardiovascular disease, and neurodegenerative diseases. Targeting lipid metabolism pathways using small molecule inhibitors or monoclonal antibodies has emerged as a promising approach to treat these diseases. An example of lipid-targeted therapy is the use of statins, which are inhibitors of HMG-CoA reductase involved in cholesterol biosynthesis. Statins have been widely used to lower cholesterol levels and reduce the risk of cardiovascular disease by inhibiting cholesterol production in the liver.

Lipids for Therapeutic Agents

Lipid compounds themselves can also be used as therapeutic agents to treat a variety of diseases. For example, omega-3 fatty acids have been shown to have anti-inflammatory, antioxidant, and neuroprotective properties and have been studied for their potential in treating cardiovascular disease, inflammatory diseases, and neurodegenerative diseases. Lipid compounds derived from natural sources, such as vegetable oils, marine oils, and microbial lipids, are also being investigated for their potential in drug development. Vegetable oils rich in bioactive lipids such as polyphenols, flavonoids and terpenoids have been shown to have anti-inflammatory, antioxidant and anti-cancer properties and have been used in traditional medicine for centuries.

Lipid Synthesis

In living organisms, lipid synthesis occurs primarily in the endoplasmic reticulum (ER) of cells, specifically in the smooth ER that lacks ribosomes. The lipid synthesis process begins with the formation of fatty acids. The first step in fatty acid synthesis is the conversion of acetyl-CoA to malonyl-CoA. It then undergoes a series of condensation reactions with acetyl-CoA to produce long-chain fatty acids. As a fatty acid chain grows, it undergoes modifications such as desaturation and elongation, forming different types of fatty acids with different chain lengths and degrees of saturation. Synthetic fatty acids can be further modified to form other types of lipids, such as phospholipids, triglycerides, and cholesterol esters. BOC Sciences has its own manufacturing facilities equipped with advanced technologies to produce lipids in large quantities. We have a team of experienced scientists and technicians who follow strict quality control processes to ensure the consistency and reliability of our lipid products. If you are interested in our lipid products, please do not hesitate to contact us promptly.

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