Summary of Cholesterol Biosynthesis

In this section we discussed the remarkable set of reactions that converts a two-carbon precursor, acetyl-CoA, into cho- 

Biosynthesis of farnesyl pyrophosphate. Farnesyl pyrophosphate is a C 5 intermediate containing three C5 isoprenoid subunits. The two transferase reactions involved in the formation of farnesyl pyrophosphate occur by virtually identical mechanisms as shown. 

Unesterified fatty acids are carried in plasma by albumin (chapter 18). The plasma also transports more complex lipids (cholesterol, triacylglycerols) among the various tissues as components of lipoproteins (spherical particles composed of lipids and proteins). Because cholesterol and triacylglyc-erol are insoluble in an aqueous medium such as the plasma, these lipoproteins (which are soluble in plasma) have evolved for the purpose of transporting complex lipids among tissues. In this section we are concerned with the structure and metabolism of these lipoproteins. 

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FIGURE 21-33 Summary of cholesterol biosynthesis. The four stages are discussed in the text. Isoprene units in squalene are set off by red dashed lines. 

From Lanosterol to Cholesterol Takes Approximately 20 Steps Summary of Cholesterol Biosynthesis Lipoprotein Metabolism... 

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