The key difference between micelles and chylomicrons is that micelles are globules of lipid molecules that are arranged in a spherical form in an aqueous solution while chylomicrons are lipoproteins that consist of a core made from triglycerides and cholesterols and a coat made from phospholipids and apolipoproteins.
Lipids are hydrophobic molecules that are non-polar and water-insoluble. They form fat globules in water. Micelles and chylomicrons are two types of fat globules. They are spherical in shape. Micelles are spherical aggregates of lipid molecules in an aqueous solution. Chylomicrons are a type of lipoproteins composed of triglycerides, cholesterols, phospholipids, proteins and apolipoproteins. They transport dietary lipids from the intestine to other tissues in the body.
CONTENTS
1. Overview and Key Difference
2. What are Micelles
3. What are Chylomicrons
4. Similarities Between Micelles and Chylomicrons
5. Side by Side Comparison –Micelles vs Chylomicrons in Tabular Form
6. Summary
What are Micelles?
Micelle is an aggregate composed of phospholipids arranged in a spherical form in an aqueous solution. They form in response to the amphipathic nature of fatty acids. Micelles consist of both hydrophilic regions and hydrophobic regions. Hydrophilic regions are polar head groups while hydrophobic regions are the long hydrophobic chains (tails). The polar head groups are hydrophilic in nature and are usually involved in the formation of the outer layer of the micelles. The hydrophobic tails are present inside the structure to prevent the interaction with water due to their non-polar hydrophobic nature.
Figure 01: Micelles
Fatty acids that are produced from micelles contain a single hydrocarbon chain in the opposite direction to two hydrocarbon chains. This structure enables the fatty acids to develop a spherical shape, lessening the steric hindrance that occurs within the fatty acid molecules themselves. The sizes of the micelles vary from 02 nm to 20 nm. The size greatly depends on the composition and concentration of micelles. Due to the amphipathic nature of the molecule, micelles form spontaneously in water as well.
In the context of the human body, micelles help in the absorption of lipid and fat-soluble vitamins such as vitamin A, D, E and K. They also help the small intestine in the absorption of essential lipids and vitamins derived from the liver and gall bladder.
What are Chylomicrons?
Chylomicrons are a type of lipoproteins made only in the endoplasmic reticulum of the intestine absorptive cells or enterocytes. They consist of phospholipids, triglycerides, cholesterol and proteins. Inside the chylomicron, there are a high amount of triglycerides and a less amount of cholesterol. Outside of the chylomicron, there are phospholipids and apolipoproteins.
Figure 02: Chylomicron
Triglycerides and cholesterol are insoluble in water. Hence, they are not soluble in plasma. In order to transport dietary lipids, they get packaged as chylomicrons, which are lipoprotein particles. Once made, chylomicrons transport dietary lipids from intestine to adipose, cardiac muscle and skeletal tissues. Lipoprotein lipases hydrolyze the triglycerides in chylomicrons and release free fatty acids in order to be absorbed by the target tissues.
What are the Similarities Between Micelles and Chylomicrons?
- Micelles and chylomicrons are fat globules.
- Both micelles and chylomicrons are made in intestine cells.
- Moreover, both these have a hydrophobic core and hydrophilic coat.
What is the Difference Between Micelles and Chylomicrons?
Micelles are aggregates of lipid molecules formed in an aqueous solution while chylomicrons are triglyceride-rich lipoproteins that are made to transport dietary lipids from intestine to adipose, skeletal and cardiac muscle tissue. So, this is the key difference between micelles and chylomicrons. Also, structurally, micelles are mainly composed of phospholipids while chylomicrons are made from triglycerides, cholesterol, phospholipids and apolipoproteins.
Moreover, micelles help in the absorption of lipid and fat-soluble vitamins such as vitamin A, D, E and K while chylomicrons transport of hydrophobic lipids from small intestine to adipose, skeletal and cardiac muscle tissues.
Below infographic tabulates the differences between micelles and chylomicrons.
Summary – Micelles vs Chylomicrons
Both micelles and chylomicrons are lipid globules formed in aqueous solutions. Micelles are simply made from phospholipids while chylomicrons are made from triglycerides, cholesterol, phospholipids and apolipoproteins. Chylomicrons are made only in the intestines in order to transport dietary lipids from the intestine to other tissues. Thus, this summarizes the difference between micelles and chylomicrons.
Reference:
1. Rahmany, Sehra, and Ishwarlal Jialal. “Biochemistry, Chylomicron”. Ncbi.Nlm.Nih.Gov, 2020, Available here.
2. “Micelle”. En.Wikipedia.Org, 2020, Available here.
Image Courtesy:
1. “Micelle scheme-en” By SuperManu – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Chylomicron” By Xvazquez – Own work (CC BY-SA 3.0) via Commons Wikimedia