What is the Difference Between Saturated and Unsaturated Fatty Acids

The main difference between saturated and unsaturated fatty acids is that the hydrocarbon chain of saturated fatty acids is made up of single bonds whereas the hydrocarbon chain of unsaturated fatty acids contains at least a single double bond. Furthermore, saturated fatty acids are solids at room temperature while unsaturated fatty acids are liquids. 

Saturated and unsaturated fatty acids are the two types of fatty acids found in food. Fatty acids are carboxylic acids with a hydrocarbon side chain. They react with glycerol to produce triglycerides. 

Key Areas Covered 

1. What are Saturated Fatty Acids
     – Definition, Saturation, Health Effects
2. What are Unsaturated Fatty Acids
     – Definition, Saturation, Health Effects
3. What are the Similarities Between Saturated and Unsaturated Fatty Acids
     – Outline of Common Features
4. What is the Difference Between Saturated and Unsaturated Fatty acids
     – Comparison of Key Differences

Key Terms 

HDL, Hydrogenation, LDL, Monounsaturated Fatty Acids (MUSF), Polyunsaturated Fatty Acids (PUSF), Saturated Fatty Acids, Unsaturated Fatty Acids 

What are Saturated Fatty Acids 

Saturated fatty acids are the fatty acids that contain single bonds between the carbon atoms in the hydrocarbon chain. Therefore, fatty acid chains are straight, allowing the fatty acid molecules to pack closely together. Saturated fatty acids are solids at room temperature. Hence, they are called fat. The melting temperature of fat is high due to the presence of a number of van der Waals forces among fatty acid molecules. Most animal fat is made up of saturated fatty acids. Due to their fully saturated nature, these fatty acids have no effect on hydrogenation. 

Figure 1: Saturated and Unsaturated Fatty Acids

Saturated fatty acids increase low-density lipoproteins (LDLs) as well as very low-density lipoproteins (VLDLs). LDL is considered a bad cholesterol since it can increase the risk of coronary heart disease.  

What are Unsaturated Fatty Acids 

Unsaturated fatty acids are the fatty acids that contain at least a single double bond in the hydrocarbon chain. The presence of double bonds causes the hydrocarbon chain to bend. Therefore, unsaturated fatty acids cannot be packed as saturated fatty acids and they maintain some distance among molecules. This is why unsaturated fatty acids are liquids at the room temperature. Hence, they are called oils, which contain a lower melting temperature than saturated fatty acids. Most fatty acids with plant origin are unsaturated. Unsaturated fatty acids can be saturated in a process known as hydrogenation. 

Figure 2: Olive Oil

Based on the degree of saturation, unsaturated fatty acids can be found in two types as monounsaturated fatty acids (MUSF) and polyunsaturated fatty acids (PUSF). Monounsaturated fatty acids contain only a single double bond in the hydrocarbon chain while polyunsaturated fatty acids contain more than one double bonds in the hydrocarbon chain. Unsaturated fatty acids increase the high-density lipoproteins (HDLs) in the body, which is considered as good cholesterol. Good cholesterol can reduce the concentration of LDL, the bad cholesterols. 

Similarities Between Saturated and Unsaturated Fatty Acids 

• Saturated and unsaturated fatty acids are the two types of fatty acids classified based on the type of bonds between carbon atoms. 
• Both are carboxylic acids with hydrocarbon side chains. 
• Also, they both involve in the formation of triglycerides. 
• Furthermore, the body requires both types of fatty acids and we can intake them through the diet. 

Difference Between Saturated and Unsaturated Fatty Acids 

Definition 

Saturated fatty acids refer to fatty acids such as stearic acid, whose carbon chain contains no unsaturated linkages between carbon atoms and cannot incorporate any more hydrogen atoms. In contrast, unsaturated fatty acids refer to fatty acids such as oleic acid, whose carbon chain possesses one or more double or triple bonds and, can incorporate additional hydrogen atoms. Thus, this describes the main difference between saturated and unsaturated fatty acids. 

Occurrence 

Saturated fatty acids can be found in coconut oil, vegetable oils, butter, whole milk, margarine, meat, and peanut while unsaturated fatty acids can be found in avocado, olive oil, canola oil, sunflower oil, fish oil, and red meat. 

Examples 

Some saturated fatty include myristic, stearic, palmitic acids while some unsaturated fatty acids are linoleic, oleic, stearidonic acids. 

Types of Bonds 

The hydrocarbon chain of saturated fatty acids only contains single bonds while the hydrocarbon chain of the unsaturated fatty acids at least contains one double bond. Chemically, this is a major difference between saturated and unsaturated fatty acids. 

Bending 

To add to the above, the hydrocarbon chain of the saturated fatty acids is a straight chain while the hydrocarbon chain of the unsaturated fatty acids is bent. 

Melting Point 

Also, the saturated fatty acids have a high melting point while unsaturated fatty acids have a low melting point. 

Physical State 

Another important difference between saturated and unsaturated fatty acids is their physical state. Saturated fatty acids are solids at room temperature while unsaturated fatty acids are liquids. 

Fat/Oils 

Moreover, the saturated fatty acids make up the fat while unsaturated fatty acids make up the oils. 

Rancidity 

Rancidity is another difference between saturated and unsaturated fatty acids. The rancidity of saturated fatty acids is low while the rancidity of unsaturated fatty acids is high. 

Shelf Life 

Besides, the shelf life of saturated fatty acids is high while the shelf life of unsaturated fatty acids is low.  

Influence on LDL 

Saturated fatty acids increase the LDL while unsaturated fatty acids decrease the LDL. This is a major difference between saturated and unsaturated fatty acids.

Recommended Consumption 

10% of calories should come from saturated fatty acids while 30% of calories should come from unsaturated fatty acids.  

Health Effects 

The excessive consumption of saturated fatty acids can lead to atherosclerosis and heart disease while the excessive consumption of unsaturated fatty acids can reduce cholesterol levels in the body. 

Conclusion 

Saturated fatty acids are the fatty acids that do not contain any double bond in the hydrocarbon chain. They are solids at the room temperature and are called fats. Most animal fat contains saturated fatty acids. Saturated fatty acids can increase bad cholesterol levels. On the other hand, unsaturated fatty acids are the fatty acids which contain at least a single double bond in the hydrocarbon chain. They are liquids at the room temperature and most plant fat contains unsaturated fatty acids. They can increase the good cholesterol levels. The main difference between saturated and unsaturated fatty acids is the degree of saturation.

Reference:

1. “Saturated Fatty Acids: Structure, Classification, Foods.” Tuscany Diet, Available Here
2. “Unsaturated Fatty Acids: Chemical Structure, Classification, Diet.” Tuscany Diet, Available Here

Image Courtesy:

1. “221 Fatty Acids Shapes-01” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia  
2. “olive-oil-salad-dressing-cooking-968657” (CC0) via Pixabay