Final answer:
The bond that joins glycerol to fatty acids in lipids like triglycerides and phospholipids is the ester linkage.
Step-by-step explanation:
The type of bond that joins glycerol to fatty acids in fat molecules and phospholipids is the ester linkage. Glycerol, which is a triol, bonds with three fatty acids, each through an ester bond, during a dehydration synthesis reaction. This reaction forms a triglyceride, which is a type of lipid essential for storing energy and providing insulation. In triglycerides, the fatty acids are attached to glycerol's three carbons through an oxygen atom, forming a strong ester bond. In the case of phospholipids, which are the major constituents of cell membranes, two fatty acid chains and a phosphate group form ester linkages with the glycerol backbone.