Final answer:
The hydrophilic property of molecules containing carboxyl groups is due to their ability to release H+ ions and form ionic and hydrogen bonds with water, making them soluble. Carboxyl groups are found in proteins and fats such as triglycerides and phospholipids.
Step-by-step explanation:
The carboxyl group makes molecules hydrophilic because it can ionize to release hydrogen ions (H+), leaving behind a negatively charged COO- group. This charged state allows the carboxyl-containing molecule to form ionic bonds and hydrogen bonds with water, which enhances the molecule's solubility in water. Macromolecules that contain carboxyl groups include proteins, which are made up of amino acids that also contain carboxyl groups, and fats, specifically the fatty acids that make up triglycerides and phospholipids.