Lipids and Biomembranes

ID #2117

Do steroids contain ester bonds?


For purposes of MCB 150, lipids are assembled through ester linkages, and this is how you should answer any question on the exam. But your question is an excellent one, and the story is more complicated than the way we present it in class (it usually is, hence my repeated use of the phrase "for purposes of MCB 150"). Lipids are not like the other macromolecules because they are categorized by a physical property not a standard structure. As we've seen, steroids look very different than phospholipids, yet both are lipids. Because they look different, it follows that the "pieces" that make them are different, and they are assembled differently. In fact, there are no ester bonds in cholesterol! We don't go into steroid biosynthesis in the course, but it's very different from phospholipd or triglyceride synthesis, which do involve esterification reactions.  Don't worry about the ones we didn't talk about in class.

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