Chapter 24

Write a balanced, stoichiometric reaction for the synthesis of phosphatidylethanolamine from glycerol, fatty acyl-CoA, and ethanolamine. Make an estimate of the \(\Delta G^{\circ}\), for the overall process.

Write a balanced, stoichiometric reaction for the synthesis of cholesterol from acetyl-CoA.

Trace each of the carbon atoms of mevalonate through the synthesis of cholesterol, and determine the source (that is, the position in the mevalonate structure) of each carbon in the final structure.

Determine the number of ATP equivalents needed to form palmitic acid from acetyl-CoA. (Assume for this calculation that each NADPH is worth 3.5 ATPs.

Write a reasonable mechanism for the 3 -ketosphinganine synthase reaction, remembering that it is a pyridoxal phosphate-dependent reaction.

Why is the involvement of FAD important in the conversion of stearic acid to oleic acid?

Write a suitable mechanism for the HMG-CoA synthase reaction. What is the chemistry that drives this condensation reaction?

Write a suitable reaction mechanism for the \(\beta\) -ketoacyl-ACP synthase, showing how the involvement of malonyl-CoA drives this reaction forward.

Insights into the function of LDL receptors in displacing IDL particles in endosomes have come from an unlikely source: a study of LDL receptor binding by a human rhinovirus HRV2 (a common cold virus). Consult suitable references to learn how this study provided support for the model of LDL particle displacement presented in this chapter. Good references are Blacklow, S. \(C ., 2004\) Nature Structural and Molecular Biology \(11: 388-390 ;\) Verdaguer, \(\mathrm{N}\) Fita, I., et al., 2004. Nature Structural and Molecular Biology 11: \(429-434 ;\) and Beglova, \(N .,\) and Blacklow, S. \(C ., 2005 .\) Trends in Bio- chemical Sciences \(30: 309-316\)