Difference Between Lipids and Fats

Main Difference – Lipids vs Fats

Lipids are a broad group of macronutrients which plays a major role as a structural molecule and an energy source. Triglycerides, phospholipids, and steroids are different types of lipids found in the body. The two types of triglycerides are fats and oils. The main difference between lipids and fats is that lipids are a broad group of biomolecules whereas fats are a type of lipids. Fat is stored in the adipose tissue and under the skin of animals. It is mainly used as an energy-storage molecule in the body. Most steroids in the body serve as hormones. Phospholipids mainly occur in the cell membrane.

Key Areas Covered

1. What are Lipids
      – Definition, Types, Characteristics
2. What are Fats
      – Definition, Types, Characteristics
3. What are the Similarities Between Lipids and Fats
     – Outline of Common Features
4. What is the Difference Between Lipids and Fats
     – Comparison of Key Differences

Key Terms: Fats, Lipids, Phospholipids, Saturated Fat, Steroids, Trans Fat, Triglycerides

What are Lipids

Lipids refer to a class of organic molecules that are insoluble in water and soluble in organic solvents. They are a diverse group of molecules. Most of the lipids are liquids. However, some lipids such as fats are solids. The three major types of lipids are triglycerides, phospholipids, and steroids. The largest class of lipids is triglycerides. Triglycerides are also called natural fats. They are esters, containing a single glycerol molecule which is attached to three fatty acid molecules. Based on the degree of saturation of the fatty acid molecules, two types of triglycerides can be identified as fats and oils. The unsaturated form of triglycerides is known as oils, and the saturated form of triglycerides is known as fats. The major function of triglycerides in the body is to serve as energy-storing molecules.

Phospholipids are a derivative of triglycerides since they contain two fatty acid molecules. The third carbon of the glycerol molecule is attached to a phosphate group. Thereby, phospholipids are amphipathic molecules in which the diglyceride part is hydrophobic while the phosphate group is hydrophilic. Phospholipids are the main structural component of the cell membrane, and they form the phospholipid bilayer. The phospholipid molecules make the cell membrane a selectively permeable barrier. The structure of the phospholipid bilayer is shown in figure 1.

Figure 1: Phospholipid Bilayer

Steroids are a type of hydrophobic molecules mostly found as cholesterol and hormones. Cholesterol is the precursor of other types of steroids in the body.

What are Fats

Fats refer to an oily substance that occurs in the body under the skin or around the organs. Since the degree of saturation of fatty acids is high, fats are typically solid at room temperature. The unsaturated fat is known as oils, which are liquids at room temperature. Typically, fats have an animal origin, and oils have a plant origin. The two types of fats are the saturated fat and the trans fat. Milk products, meat, butter, and cheese are the major sources of dietary saturated fat. The consumption of saturated fat is good for the health since it increases the levels of good cholesterol or the high-density lipoprotein (HDL), which lowers the risk of cardiovascular disease.

Figure 2: Food containing Fat

Trans fat is produced by the partial dehydrogenation of liquid vegetable oils. It contains a single, double bond in its structure. Due to the high degree of saturation, trans fats are also solids at room temperature. The consumption of more trans fat is bad for the health since it increases the levels of bad cholesterol in the blood and decreases the levels of good cholesterol.

Similarities Between Lipids and Fats

Both lipids and fats are types of molecules found in the animal body.
Both lipids and fats are used as energy sources in the body.
Both lipids and fats are insoluble in water and soluble in the organic solvents.
Both lipids and fats are broken down by a group of enzymes called lipases.

Definition

Lipids: Lipids are a class of organic molecules that are insoluble in water and soluble in organic solvents.

Fats: Fats are an oily substance found in the body, under the skin or around the organs.

Correlation

Lipids: Lipids are a diverse group of biomolecules found in the animal body.

Fats: Fats are a type of lipids.

Types

Lipids: Triglycerides, phospholipids, and steroids are the three types of lipids.

Fats: Saturated fat and trans fat are the two types of fats.

Physical Status

Lipids: Some lipids are solid, and others are liquids.

Fats: Fats are solid substances.

Function

Lipids: Lipids serve as a structural component as well as an energy molecule in the body.

Fats: Fats are used as an energy source.

Conclusion

Lipids and fats are two types of biological molecules in the animal body. Both lipids and fats are only soluble in organic solvents. Lipids are a diverse group of biomolecules, consisting of triglycerides, phospholipids, and steroids. Fats are a type of triglycerides, which are solid at room temperature due to their high degree of saturation. The main difference between lipids and fats is the types of molecules.

Reference:

1. Helmenstine, Anne Marie. “What Are the Types of Lipids and Where They Are Found?” ThoughtCo, Available here.
2. “Types of Fat.” The Nutrition Source, 21 Sept. 2017, Available here.

Image Courtesy:

1. “0302 Phospholipid Bilayer” By OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Fatty foods” By Lucasmartin2 – Own work (CC BY-SA 4.0) via Commons Wikimedia