Medical College Admission Test (MCAT) Practice Exam 2025 - Free MCAT Practice Questions and Study Guide

All triglycerides share a common structural feature in that they are built upon a glycerol backbone. This glycerol molecule is a three-carbon alcohol, and it serves as the foundational structure to which the fatty acid components are attached. In a triglyceride, three fatty acid molecules are esterified to the glycerol, forming the characteristic structure of these lipids.

While other elements such as ester linkages and fatty acid tails are also present in triglycerides, these are not unique to triglycerides alone. The glycerol backbone is distinctive and gives triglycerides their identity as a specific type of lipid, distinguishing them from other lipid classes such as phospholipids, which incorporate a phosphate group in their structure. Hence, the presence of the glycerol backbone is what defines all triglycerides uniformly.