Chris Somerville
John Browse
Jan G. Jaworski
John B. Ohlrogge

The term lipid refers to a structurally diverse group of molecules that are preferentially soluble in a nonaqueous solvent such as chloroform. Lipids include a wide variety of fatty acid–derived compounds, as well as many pigments and secondary compounds that are metabolically unrelated to fatty acid metabolism. Although we will limit our discussion of lipids to those compounds with origins in fatty acid synthesis, this limitation still provides a broad group of compounds to explore, many of which are vital to the normal functioning of a cell. Each plant cell contains a diverse range of lipids, often located in specific structures. Furthermore, different plant species may contain different lipids.
      Although the metabolism of fatty acids and lipids in plants has many features in common with other organisms, the lipid pathways in plants are complex and not well understood. The complexity arises primarily from cellular compartmentalization of the pathways and the extensive intermixing of lipid pools between these compartments (Fig. 10.1). In addition, higher plants collectively accumulate more than 200 different fatty acids, so there are many open questions about the nature of the enzymes involved in the synthesis of these compounds. Among the many challenges facing plant biochemists today is the complete elucidation of these pathways and the mechanisms that regulate them.