Question

Lipids are insoluble in water because lipids molecules are 

• A. Hydrophilic
• B. Hydrophobic
• C. Neutral
• D. Zwitter ions

Answer 1

The Correct Option is B

To understand why lipids are insoluble in water, we need to delve into some basic chemistry principles concerning polar and non-polar substances.

Water is a polar molecule, meaning it has a positive and a negative end. Because of this polarity, water molecules are very good at dissolving other substances that are also polar (like salt) or that can ionize (like acids). However, substances that are non-polar do not dissolve well in water. This is because there is no charge for water molecules to interact with, and non-polar molecules do not form favorable interactions with water molecules.

Lipids, such as fats and oils, are composed primarily of long chains of hydrocarbons which are non-polar. This lack of polarity means there are no positive or negative poles, thereby preventing any strong interaction with water molecules. Therefore, lipids are hydrophobic, which means "water-fearing". They do not mix or dissolve in water. Instead, they repel water. This hydrophobic nature is responsible for lipids forming separate layers when mixed with water, such as oil droplets floating on the surface of water.

Let's evaluate the options provided:

• Hydrophilic: This term means "water-loving" and describes substances that dissolve well in water. This is the opposite of lipids.
• Neutral: While lipids can be electrically neutral, this property is not directly related to their solubility in water.
• Zwitter ions: These are molecules that have both a positive and negative charge. Lipids are not zwitter ions, as they lack such charged groups.

Thus, the correct answer is that lipids are hydrophobic. This property explains their insolubility in water.