Final answer:
Lipids are hydrophobic compounds that provide body fuel and are important components of many biological compounds. Triglycerides, phospholipids, and steroids are all lipids and have different structures and functions.
Step-by-step explanation:
Lipids are hydrophobic compounds that provide body fuel and are important components of many biological compounds. Triglycerides are the most abundant lipid in the body, and are composed of a glycerol backbone attached to three fatty acid chains. Phospholipids are compounds composed of a diglyceride with a phosphate group attached at the molecule's head. The result is a molecule with polar and nonpolar regions. Steroids are lipids formed of four hydrocarbon rings. The most important is cholesterol. Prostaglandins are signaling molecules derived from unsaturated fatty acids.