The key difference between lipophilic and hydrophilic is that lipophilic substances tend to combine with or dissolve in lipids or fats and other lipophilic solvents whereas hydrophilic substances tend to combine with or dissolve in water and other hydrophilic solvents.
The terms lipophilic and hydrophilic are adjectives we use to name substances according to their solubility. A lipophilic substance have the property of lipophilicity; likewise, hydrophilic substances have the property of hydrophilicity.
CONTENTS
1. Overview and Key Difference
2. What is Lipophilic
3. What is Hydrophilic
4. Side by Side Comparison – Lipophilic vs Hydrophilic in Tabular Form
5. Summary
What is Lipophilic?
Lipophilic refers to the ability of a substance to dissolve in lipids or fats. Since lipids and fats are nonpolar, lipophilic substances are also nonpolar (according to “like dissolves like” rule). The term lipophilicity often correlates with biological activities; it is the single most important physical property that affects the potency of a drug to distribute throughout the body and to eliminate from the body.
Figure 01: Lipids are Lipophilic
Many lipophilic substances (ex: fat-soluble vitamins, cholesterol, triglycerides) are essential for life. Therefore, our body must absorb and transport them to the target efficiently. However, the body fluid is mostly hydrophilic; thus, these substances cannot dissolve in it. Therefore, the body uses “carriers” which can bind with lipophilic substances, and they carry them to the target.
What is Hydrophilic?
Hydrophilic refers to the ability of a substance to dissolve in water or other hydrophilic solvents. Here also, the “like dissolve like” rule is applied. The substances that are hydrophilic are called hydrophiles. They get attracted to water molecules and form interactions with them, thus, eventually getting dissolved. On the other hand, the substances that do not dissolve in water are “hydrophobes”.
Figure 02: Hydrophilic and Hydrophobic Parts of Cell Membrane
Hydrophilic substances are essentially polar molecules (or a portion of molecule). They are capable of forming hydrogen bonds. Sometimes, substances have both hydrophilic and hydrophobic portions. The hydrophobic portion can be lipophilic (or not). Examples for hydrophilic substances include compounds with hydroxyl groups such as alcohols.
What is the Difference Between Lipophilic and Hydrophilic?
The solubility of a compound in a solvent depends on the chemical structure of the compound. Lipophilic substances have nonpolar structure, and hydrophilic compounds have polar structures. Besides, the key difference between lipophilic and hydrophilic is that lipophilic substances tend to combine with or dissolve in lipids or fats and other lipophilic solvents whereas hydrophilic substances tend to combine with or dissolve in water and other hydrophilic solvents. Examples for lipophilic substances include fat-soluble vitamins, hormones, amino acids, hydrocarbon compounds, etc. while examples of hydrophilic substances include alcohols, sugars, salt, soap, etc.
Summary – Lipophilic vs Hydrophilic
The terms lipophilic and hydrophilic are adjectives which describe the solubility of compounds. The key difference between lipophilic and hydrophilic is that lipophilic refers to the ability of a substance to dissolve in lipids or fats while hydrophilic refers to the ability of a substance to dissolve in water or other hydrophilic solvents.
Reference:
1. “Transport of Lipophilic Substances .” com, Laboratory Continuing Education, Available here.
Image Courtesy:
1. “Common lipids lmaps” By Lmaps at the English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “0302 Phospholipid Bilayer” By OpenStax – (CC BY 4.0) via Commons Wikimedia