Liquid oils (predominant in plants) have unsaturated fatty acids, sometimes with shorter hydrocarbon chains. Solid fats (predominant in animals) are triacylglycerols with long (16-18 carbon) saturated fatty acids. If you go on to take a biochemistry course, you will learn more about the big picture of fatty acid metabolism - how it is regulated, and how is fits together with other pathways of central metabolism.įats and oils are forms of triacylglycerol, a molecule composed of a glycerol backbone with three fatty acids linked by ester functional groups.

We will learn about the details of all of the reactions in these metabolic pathways at various places in this book. The breakdown of fatty acids in the body also occurs two carbons at a time, and the endpoint is again acetyl-coenzyme A. We will see much more of coenzyme A when we study the chemistry of thioesters in chapter 11.

Each two-carbon unit is derived from a metabolic intermediate called acetyl-coA, which is essentially an acetic acid (vinegar) molecule linked to a large 'carrier' molecule, called coenzyme A, by a thioester functional group. The double bonds in naturally occurring fatty acids are predominantly in the cis configuration.įatty acids are synthesized in the body by a process in which the hydrocarbon chain is elongated two carbons at a time. Saturated fatty acids contain only alkane carbons (single bonds only), mononsaturated fatty acids contain a single double bond, and polyunsaturated fatty acids contain two or more double bonds. Fats, oils, and waxes all incorporate fatty acids, which are composed of hydrocarbon chains terminating in a carboxylic acid/carboxylate group (we will learn in Chapter 7 that carboxylic acids are predominantly in their anionic, carboxylate form in biological environments). Lipids are a class of biomolecules which includes fats, oils, waxes, and compounds such as cholesterol that are referred to as 'isoprenoids'.

Structure of lipids download