Chapter 3, Problem 1.1Q

Summary Introduction

To determine: Why some triglycerides are in liquid form while others are in solid form at room temperature?

Introduction: The lipids are non-polar hydrophobic molecules that include phospholipids, waxes, oils, steroids, and fats which make up the biological membranes. Structurally and functionally, the lipids are a diverse group of compounds. They are defined by their nature of insolubility in water.

Explanation of Solution

Triglycerides are the simple lipids that have three fatty acids joined with one molecule of glycerol. The triglycerides are hydrophobic. Since the fatty acids in the triglycerides possess the maximum possible amount of hydrogen, they would be called as saturated fats. In the saturated fatty acids, all bonds present between the carbon atoms in the hydrocarbon chain possess single bonds. They are relatively straight molecules and are able to tightly pack together. This makes the triglycerides to remain in a solid-state at room temperature. The molecular structure of unsaturated fats makes them liquid at room temperature. In unsaturated fatty acid, the hydrocarbon chain possesses one or more double bonds between the carbon atoms. The double bonding between the carbon atoms results in kinks that prevent them from tight packing. Thus, they have relatively lower melting point.