GlycerolThe backbone of the molecule. Each of its three carbons holds one fatty acid.
Saturated fatty acidA fatty acid with no double bonds. Its chain is straight.
Unsaturated fatty acidA fatty acid with one or more double bonds. A double bond puts a bend in the chain.
How they join 7
Hydroxyl groupAn oxygen and a hydrogen on the glycerol. Glycerol has three, one for each fatty acid.
Carboxyl groupThe acid end of a fatty acid. It is the end that joins to the glycerol.
Hydrocarbon chainThe long tail of a fatty acid. It is a chain of carbon atoms that carry hydrogen.
Double bondTwo bonds between neighboring carbons. It is rigid and puts a kink in the chain.
Omega endThe far end of the chain, opposite the carboxyl group. Its last carbon is the omega carbon.
Ester bondThe link left when a carboxyl group joins a hydroxyl group. A triglyceride has three.
Water moleculeGiven off each time a fatty acid joins. Three joins release three water molecules.
How this list was compiled: Every name was checked on 2026-10-01 and kept only where two independent sources use it. (1) Wikipedia, text only: Triglyceride, https://en.wikipedia.org/wiki/Triglyceride ; Fatty acid. (2) Kimball's Biology Pages, Fats, https://www.biology-pages.info/F/Fats.html . (3) The American Heritage Dictionary of the English Language, fifth edition, https://www.ahdictionary.com/ : triglyceride, ester, fatty acid, glycerol. E. V. Wong, Cells: Molecules and Mechanisms, chapter 2 (an open college textbook), was read for the ester bond, the carboxyl group and saturated and unsaturated chains. Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
A triglyceride is a fat molecule. The 4 parts of a triglyceride are one glycerol and three fatty acids. The first drawing shows them; the second shows how a fatty acid joins the glycerol.
Read the full guide
Straight chain or bent chain
A saturated fatty acid has only single bonds between its carbons, so its chain runs straight. An unsaturated fatty acid has at least one double bond, and the chain bends there.
Three joins, three water molecules
Glycerol has three hydroxyl groups. Each reacts with the carboxyl group of one fatty acid. A water molecule comes off, and an ester bond is left holding the two together.
Tri means three: three fatty acids, three ester bonds, three water molecules given off.
Questions and answers
What are the four parts of a triglyceride?
One molecule of glycerol and three molecules of fatty acid. The three fatty acids may be alike or different, and each is joined to a different carbon of the glycerol.
What are the 2 main parts of a lipid?
For a fat, the two kinds of building block are glycerol and fatty acids. A fat molecule has one glycerol and three fatty acids. Other lipids are built differently: a phospholipid, for example, has two fatty acids and a phosphate group.
What is the difference between saturated and unsaturated fatty acids?
A saturated fatty acid has no double bonds between its carbons, so it holds as many hydrogen atoms as it can. An unsaturated fatty acid has one or more double bonds, and each one puts a kink in the chain.
What bond holds a triglyceride together?
An ester bond. It forms where the carboxyl group of a fatty acid meets a hydroxyl group of the glycerol, and a water molecule is given off. A triglyceride has three ester bonds.