What is the Difference Between Triacylglycerol and Triglyceride

The main difference between triacylglycerol and triglyceride is that triacylglycerol is the correct chemical name for an ester derived from glycerol bound to three fatty acids whereas triglyceride is the common name for the substance. Triglycerides are the main constituent of the animal and vegetable fats in the diet. Moreover, they are the main constituent of the fat stores of the body as well.

Triacylglycerol and triglyceride are two names used to describe a simple type of lipid present in both animal and plant body.

Key Areas Covered

1. What is Triacylglycerol
     – Definition, Structure, Occurrence
2. What is Triglyceride
     – Definition, Types, Role
3. What are the Similarities Between Triacylglycerol and Triglyceride
     – Outline of Common Features
4. What is the Difference Between Triacylglycerol and Triglyceride
     – Comparison of Key Differences

Key Terms

Body Fat, Ester, Fatty Acids, Glycerol, Saturated Fat, Triacylglycerol, Triglyceride, Unsaturated Fat

What is Triacylglycerol

Triacylglycerol (TAG) is the chemical name for the esters derived from glycerol and three fatty acids. It is the main constituent of the body fat in humans and other animals. Liver transforms blood glucose into triacylglycerol in order to deposit in the adipose tissue. Therefore, triacylglycerol occurs in the blood as well. In addition, it is the main constituent of the human skin oils. Also, it is the main constituent of vegetable fat.

Figure 1: Triglyceride Structure

Usually, there are many kinds of triacylglycerol due to the variability in the chain length of fatty acids. However, most fatty acids in triacylglycerol contain 16, 18, and 20 carbon atoms in their carbon chains. Since fatty acid biosynthesis occurs through acetyl-CoA, a two-carbon building block, natural fatty acids in animals and plants contain an even number of carbon atoms. However, bacteria produce fatty acids with branched chains and an odd number of carbon atoms. Also, due to the presence of bacteria inside the ruminant digestive system, the fat from the ruminant animals contain fatty acids with an added number of carbon atoms.

What is Triglyceride

Triglyceride (TG) is the common and the widely used name for the triacylglycerol. The two main types of triglycerides are saturated and unsaturated fats. Here, all the carbon atoms in the fatty acid chains of saturated fats are bonded to each other only through single bonds. That means; all the bonds are fully saturated with hydrogen atoms. Therefore, saturated fats have high melting points and they exist as solids at room temperature. Most animal fats are saturated fats. In comparison, most vegetable fats are unsaturated fats which remain as oils at room temperature. They contain at least a single double bond in the fatty acid chain. Here, the fatty acid chains with a single double bond are monounsaturated fats while the fatty acid chains with two or more double bonds are polyunsaturated fats.

Figure 2: Saturated and Unsaturated Fatty Acids

Moreover, since triglycerides are the main form of dietary fat, lipase is the enzyme responsible for the hydrolysis of this fat in the gut into fatty acids and monoglycerides. However, the re-esterification of monoglycerides in enterocytes forms chylomicrons ultimately mixed into the blood. Then, tissues of the body can capture them to use as an energy source. Liver and adipose tissue are the main sites for the endogenous triglyceride synthesis. Therefore, triglycerides in the adipose tissue represent one of the energy sources of the body. The enzymatic action of the hormone-sensitive lipase is responsible for the mobilization of fatty acids in the adipose tissue. Also, very low-density lipoproteins (VLDL) are the main secretion form of fatty acids from the liver.

Similarities Between Triacylglycerol and Triglyceride

• Triacylglycerol and triglyceride are two names that describe a simple ester with three fatty acids bound to a glycerol backbone.
• They are the main constituent of animal and vegetable fat.
• Also, they are the main constituent of the body fat.

Difference Between Triacylglycerol and Triglyceride

• ‘Triacylglycerol’ is the correct chemical name for a simple ester with three fatty acids bound to a glycerol backbone while ‘triglyceride’ is the common name for the same substance.

Conclusion

Triacylglycerol is the chemical name for the esters, which contains three fatty acids bound to a glycerol backbone. However, the triglyceride is the common name used to describe the same substance. Triacylglycerol or triglyceride is the main constituent of our body fat, animal fat, and vegetable fat. Therefore, the main difference between triacylglycerol and triglyceride is their usage.

References:

1. “Triacylglycerol.” ScienceDirect, Elsevier, 2009, Available Here

Image Courtesy:

1. “Eie-TRIGLYCERIDE” (CC BY-SA 3.0) via Commons Wikimedia  
2. “Fatty Acids” By AJC1 (CC BY-SA 2.0) via Flickr