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Lipids - Triacylglycerols, Phospholipids and Sterols

Lipids the name belongs to the mixture of biology and chemistry. Lipids are a type of organic molecule which is found in almost all living things. The texture of lipids will be oily or waxy. Major fats are composed of lipid molecules. These lipids can be identified in almost all such as algae, seeds, meat, cheese, butter and fish. Lipids are water-insoluble and they are formed when fatty acids react with glycerol. Those fatty acids are classified as saturated and unsaturated fatty acids. 

What do the lipids constitute?

Well, they are made up of long chains of carbon and hydrogen molecules. They are divided into two, simple and complex.
Simple lipids are non-polar soluble organic compounds, eg. Chloroform and Benzene. Complex lipids would be fatty acids with alcohol, eg. Cell membranes, nerve tissues and blood platelets.

Where do they occur in the human body?

They occur naturally as molecules in the human body which include fats, waxes, steroids, vitamins (which are fat soluble), glycerides, phospholipids, and others. The functions of lipids are mainly used for storing energy, signaling and stimulating the components of cell membranes. Lipids are generally classified as:

          1. Triacylglycerols
          2. Phospholipids
          3. Sterols


The triacylglycerols are the major form of fat stored by the body. They are made up of 3 molecules of fatty acids added with a molecule of glycerol, which serves as a backbone in many types of lipids. These type of lipids are commonly found in fried foods, vegetable oil, butter, creamed milk and milk cheese, cheese and sweats. They are also found in avocados, olives, corn and nuts. They do not solve in water.

A higher number of Triacylglycerols results in swelling of pancreas and hardening of arteries. The remedial for the high Triacylglycerols would be in the diet plan as mentioned in the table is given below.

S. NoChecklist
1Olive oil
5Exercise regularly
6Eat at proper time

The following table explains the awareness on Triacylglycerols.

S. NoChecklist
1Weight loss
2Limit on sugar
3Intake healthy fats
4Limit on starch
5Limit on alcohol
6Do regular exercise
7Intake high protein

The normal range for Triglycerides would be 30–149 mg/dL.
The normal range for Cholesterol would be 0–199 mg/dL.
Triglycerides are the fats captivated in the blood following a meal or made by the liver in response to diets rich in sugars, refined carbohydrates, or fats.
Excess of triglycerides is seen in obese people.
Excess of triglycerides increases the level of LDL which may give rise atherosclerosis.


Lipids are a constituent of the cell membrane (Phospholipids). Phospholipids undergo degradation into arachidonic acid which is 20 carbon containing fatty acid. This is used in the synthesis of eicasanoic.

Eg: Prostaglandins, leukotriene, Lipoxins, Prostacyclins, Thromboxane

Phospholipids are made up of a chemical compound having hydrophilic and lipophilic properties. Each phospholipid contains a negatively charged phosphate group and glycerol. It follows 2% of the dietary lipids and water-soluble. They are available in the body's cell membranes. The structure of the phospholipid molecule consists of two hydrophobic fatty acid "tails" and a hydrophilic "head". The two components are attached together by a glycerol molecule. With simple organic molecules such as choline, ethanolamine or serine, the phosphate groups can be modified.

These are widely used in the preparation of liposomal, ethosomal and different nano-formulations of topical, oral and parental drugs for improved bio-availability, reduced toxic and increased accessibility among membranes.

Liposomal is composed of phosphatidylcholine which is of high in phospholipids and contains mixed phospholipid chains with surfactant properties. The ethosomal formulation of ketoconazole using phospholipids is a gifted option for transdermal delivery in fungal infections.

The lists of available sources of mechanically created phospholipids are soya, rapeseed, sunflower, chicken eggs, bovine milk, fish eggs etc. Each source has a unique profile and consequently differing applications in food, nutrition, pharmaceuticals, cosmetics and drug delivery.


Sterols also commonly called steroid alcohols, which are a subgroup of the steroids and plays a vital role in the class of organic molecules. They occur obviously in plants, animals, and fungi, and can be also formed by a number of bacteria. Cholesterol is the most familiar type of animal sterol. This is vital to cell membrane structure and functions as a precursor to fat-soluble vitamins and steroid hormones. The best Sterols are the cholesterol that is even if the body consumes less cholesterol through food, the body produces mostly high of it.

The Sterols which are available in plants are called phytosterols and available in animals are called zoosterols. The most significant zoosterol is cholesterol; prominent phytosterols incorporate campesterol, sitosterol, and stigmasterol. Ergosterol is a sterol which is present in the cell membrane of fungi, where it serves a role similar to cholesterol in animal cells.

Sterols are a collection of steroids which forms a hydroxyl group of the A-ring. They are amphipathic lipids synthesize from acetyl-coenzyme. The overall molecule is flat. The hydroxyl group is polar. The remaining of the aliphatic chain is non-polar.
The exogenous form of lipids which we consume through the food is mainly triglyceride. It is the stored form for lipids. Lipids get mainly stored in adipose tissue. Adipose tissue secretes a hormone called leptin which regulates appetite. Fats form an essential constituent of greater momentum which is called as the policemen of the abdomen. Lipids help in conservation of water. Hydrolysis of lipids gives nearly 1 ml of water. 

Sudden infant death syndrome mainly occurs due to a defect in metabolism involving lipids, so that when a infant suffers from starvation for more than 12 hrs, due to gluconeogenesis, the infant dies.

In cancer cells, due to Warburg effect, the acetyl co-a of PPA cycle is diverted towards lipogenesis.

Lipids are the main source of energy in our body. Excess of carbohydrates and proteins in our body it gets stored only in the form of lipids (Fats). During starvation, the energy is provided by the gluconeogenesis pathway, in which the substrates are mainly fat (break down product of fats) and amino acids. 

Lipid signaling entails a lipid messenger that is used for combining a protein target. The protein target can be a receptor, phosphatase or kinase. Lipid signaling is consideration to be qualitatively far removed from other classical signaling paradigms since lipids can generously diffuse through membranes. One conclusion of these lipid messengers is that they cannot be stored in vesicles former to discharge and are often biosynthesized "on demand" at their proposed site of achievement. 

The basic lipids blood test actions on total cholesterol, triglyceride levels, HDL and LDL cholesterol. More extensive lipid profile testing includes VLDL, the ratio of total cholesterol to HDL, and the ratio of LDL to HDL.

Lipid profile testing is used to find out the risk of heart disease along with other factors such as age, family history, cigarette smoking, diet, exercise, weight, blood pressure, and diabetes.

The medical doctor will also use lipids blood test panel or lipid profile to monitor the dealing if an individual is prescribing a lipid-lowering medication such as a static.

Cholesterol is needed for the synthesis of steroid hormones and bile. It is a necessary component of cell membranes. Most people receive a high amount of cholesterol from their diet resulting in high cholesterol levels (greater than 200 mg/dL). The total cholesterol is the measurement by adding High-Density Lipoprotein (HDL), Low-Density Lipoprotein (LDL), and Very Low-Density Lipoprotein (VLDL).

Low total cholesterol levels are normally preferred, but particularly low levels (LDL cholesterol levels less than 50 mg/dl) can decrease hormone levels and which results in issues with memory and cognition.
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