Lecture23-2010-Cholesterol

Lecture23-2010-Cholesterol - 1 Cholesterol Biosynthesis...

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Unformatted text preview: 1 Cholesterol Biosynthesis Lecture 23 Chapter 20-7 Office hour on lecture days only 11:00 am-12:00 pm Huilin.Li@StonyBrook.edu Objectives 1. Understand that acetyl-CoA is converted to cholesterol. 2. Understand how cholesterol synthesis is regulated by the amount of HMG-CoA reductase 3. Understand that the LDL receptor keeps circulating cholesterol low. 4. Know that abnormal cholesterol transport leads to atherosclerosis. 2 3 Cholesterol Functions Essential component of membranes: modulates fluidity and permeability . Precursor for bile salts : natural detergents in gut. Precursor for steroid hormones : e.g. estrogens, testosterone. Made from Acetyl-CoA More Nobel prizes (13!) given for understanding synthesis/metabolism than for any other molecule. 4 Chole ster ol is synthesized from Acetyl-CoA Figure 9-10a 27C (2C -> 1 Nobel prize) OH group at C3 5 Cholesterol is the precursor to steroid hormones: Figure 9-11 6 Cholesterol is the precursor to bile acids: Figure 20-1 7 Cholesterol Biosynthesis Four stages: 1. Acetyl-CoA to HMG-CoA to isopentenyl- pyrophosphate (C5). 2. Condensation of 6 isopentyl- pyrophosphates to make squalene (30C). 3. Cyclization of squalene to make lanosterol. 4. Modifications of lanosterol to make cholesterol. 8 Isopentenyl-pyrophosphate is an isoprene: Page 721 9 HMG-CoA made from 3 molecules of Acetyl-CoA (cytosolic isozymes of those for Ketone Body synthesis): Figure 20-21 10 Synthesis of isopentenyl- pyroposphate: Recall HMG-CoA made during Ketone Body synthesis in mt ....
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This note was uploaded on 11/19/2010 for the course BIO 361 taught by Professor Lake during the Fall '08 term at SUNY Stony Brook.

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Lecture23-2010-Cholesterol - 1 Cholesterol Biosynthesis...

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