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CHEM204: Bioorganic Chemistry

Unit 3: Lipid Metabolism   The term “lipid” refers to a broad group of hydrophobic biomolecules.  This family of compounds includes fats, waxes, steroids, fat-soluble vitamins (such as vitamins A, D, E, and K), and phospholipids, just to name a few.  While most lipids are hydrophobic, some are amphiphilic, meaning that they possess a hydrophilic head and a hydrophobic tail.  This property enables them to form vesicles and membranes in aqueous environments.  Hydrophobic chemicals can be dissolved into the membrane.  The primary biological functions of lipids in living organisms include plasma membrane building, energy storage, enzyme regulation, and signaling.  This unit explains the biosynthesis and biodegradation of lipids.

Unit 3 Time Advisory
This unit should take you approximately 21.5 hours to complete.

☐    Subunit 3.1: 2.5 hours

☐    Subunit 3.2: 1 hour

☐    Subunit 3.3: 2 hours

☐    Subunit 3.4: 3 hours

☐    Subunit 3.5: 5 hours ☐    Subunit 3.5.1: 2 hours

☐    Subunit 3.5.2: 1.5 hours

☐    Subunit 3.5.3: 1.5 hours

☐    Subunit 3.6: 3.5 hours

☐    Subunit 3.7: 4.5 hours

Unit3 Learning Outcomes
Upon successful completion of this unit, the student will be able to:
- Explain lipid transport within the cell. - Compare and contrast fatty acid biosynthesis and fat catabolism in the cell. - Compare and link terpenoid and steroid biosynthesis. - Explain why certain lipids are essential and others are not.

3.1 Triacylglycerol Turnover   3.1.1 Triacylglycerol Hydrolysis   - Reading: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Lipoproteins: Lipid Digestion & Transport” Link: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Lipoproteins: Lipid Digestion & Transport” (HTML)
 
Instruction: Please click on the link above, select the “Lipid Digestion” under the “Contents of this page” heading,and study the paragraphs on bile acids, pancreatic lipase, phospholipase A, and cholesteryl esters, which describe the first four images.
 
Studying this resource will take approximately 1 hour to complete.
 
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  • Reading: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Lipid Catabolism: Fatty Acids & Triacylglycerols” Link: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Lipid Catabolism: Fatty Acids & Triacylglycerols” (HTML)
     
    Instruction: Please click on “Fatty Acids & Triacylglycerols” under the “Contents of this page” heading, and study the paragraphs until the "Fatty Acid Activation" section; these paragraphs describe the first three images.  Note that the last two sentences on fatty acid transport go beyond the scope of this course.
     
    Studying this resource will take approximately 30 minutes to complete.
     
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3.1.2 Triacylglycerol Resynthesis   - Reading: James Hutton Institute: William W. Christie’s “Triacylglycerols” Link: James Hutton Institute: William W. Christie’s “Triacylglycerols” (HTML)
 
Instruction: Please click on the link above, and study the “1. Biosynthesis of Triacylglycerols” and “5. Triacylglycerol Metabolism in Plants and Yeasts” sections on this webpage.  
 
Studying this resource should take approximately 1 hour to complete.
 
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3.2 Triacylglycerol Catabolism: The Fate of Glycerol   - Reading: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Glycolysis and Fermentation” Link: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Glycolysis and Fermentation” (HTML)
 
Instruction: Please click on the link above, select the “Glycolysis Pathway” link under the “Contents of this page” heading, scroll down to the “4. Aldolase Catalyzes” section, and study this entire section.  Glycerol is converted to dihydroxyacetone phosphate (see Subunit 3.1.1 of this course), which in turn is an intermediate of glycolysis.  Thus, glycerol can be used in the glycolytic pathway.  
 
Studying this resource will take approximately 1 hour to complete.
 
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3.3 Triacylglycerol Catabolism: Fatty Acid Oxidation   - Reading: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Lipid Catabolism: Fatty Acids & Triacylglycerols” Link: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Lipid Catabolism: Fatty Acids & Triacylglycerols” (HTML)
 
Instruction: Please click on the link above, select “Fatty Acid b-Oxidation” under the “Contents of this page” heading, and study the “b-Oxidation Pathway” and “ATP Production” sections on this page.  Note that “b-Oxidation” is generally called β-oxidation.  
 
Studying this resource will take approximately 2 hours to complete.
 
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3.4 Fatty Acid Biosynthesis   - Reading: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Fatty Acid Synthesis” Link: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Fatty Acid Synthesis” (HTML)
 
Instruction: Please click on the link above, and study this entire webpage.  Chain elongation during fatty acid synthesis is a series of Claisen condensations.  These redox reactions are catalyzed by multi-subunit fatty acid synthases.  
 
Studying this resource will take approximately 3 hours to complete.
 
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3.5 Terpenoid Biosynthesis   3.5.1 The Mevalonate Pathway To Isopentenyl Diphosphate   - Reading: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Cholesterol Synthesis” Link: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Cholesterol Synthesis” (HTML)
 
Instruction: Please click on the link above, and then select the “HMG-CoA formation and conversion to mevalonate” link under “Contents of this page,” and study this section.  The section ends with the production of mevalonate.  
 
Studying this resource will take approximately 2 hours to complete.
 
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3.5.2 The Deoxyxylulose Pathway To Isopentenyl Diphosphate   - Reading: National Center for Biotechnology Information’s PubMed: Proceedings of the National Academy of Sciences of the United States of America: Felix Rohdich’s “The Deoxyxylulose Phosphate Pathway of Isoprenoid Biosynthesis: Studies on the Mechanisms of the Reactions Catalyzed by IspG and IspH Protein” Link: National Center for Biotechnology Information’s PubMed: Proceedings of the National Academy of Sciences of the United States of America:Felix Rohdich’s “The Deoxyxylulose Phosphate Pathway of Isoprenoid Biosynthesis: Studies on the Mechanisms of the Reactions Catalyzed by IspG and IspH Protein” (HTML)
 
Instruction: Please click on the link above, and study the introduction of this publication.  The introduction starts right after the "Keywords" and it includes "Figure 1: The deoxyxylulose phosphate pathway of isoprenoid biosynthesis."  Make sure to write notes when you study this section. Check your knowledge: write down the isoprenoid biosynthesis pathway without looking at Figure 1 on the webpage.
 
Studying this resource will take approximately 1 hour and 30 minutes to complete.
 
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3.5.3 Conversion of Isopentenyl Diphosphate to Terpenoids   - Reading: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Cholesterol Synthesis” Link: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Cholesterol Synthesis” (HTML)
 
Instruction: Please click on the link above, and select "Conversion of mevalonate to isoprenoid precursors" under the “Contents of this page” heading, and study the four images and the associated text in this section.  Check your knowledge: write down the isopentenyl pyrophosphate and the farnesyl pyrophosphate biosynthesis pathways without looking at the figures on the webpage.
 
Studying this resource will take approximately 1 hour and 30 minutes to complete.
 
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3.6 Steroid Biosynthesis   3.6.1 Synthesis of Squalene and its Conversion to Lanosterol   - Reading: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Cholesterol Synthesis” Link: Rensselaer Polytechnic Institute: Joyce J. Diwan’s “Cholesterol Synthesis” (HTML)
 
Instruction: Please click on the link above, and then select “Synthesis of squalene and its conversion to lanosterol” under the “Contents of this page” heading.  Study the pathway summary image right of “Squalene Synthase.” Check your knowledge: write down the lanosterol biosynthesis pathway without looking at the figure on the webpage.
 
Studying this resource will take approximately 1 hour and 30 minutes to complete.
 
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3.6.2 Conversion of Lanosterol to Cholesterol   - Reading: Rensselaer Polytechnic Institute: Joyce J. Diwan's "Cholesterol Synthesis" Link: Rensselaer Polytechnic Institute: Joyce J. Diwan's "Cholesterol Synthesis" (HTML)
 
Instruction: Please click on the link above, then select the "Conversion of Lanosterol to Cholesterol" link under the “Content on this page” heading, and study the first image.  Then, under the “Content on this page,” click on "Regulation of cholesterol synthesis and pharmaceutical intervention," and study until the end of the webpage.
 
Studying this resource will take approximately 2 hours to complete.
 
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3.7 Clinical Significance of Lipid Metabolism   - Reading: The Medical Biochemistry Page: Michael W. King’s “Clinical Significance of Fatty Acids” Link: The Medical Biochemistry Page: Michael W. King’s “Clinical Significance of Fatty Acids” (HTML)
 
Instruction: Please click on the link above, and read the entire “Clinical Significance of Fatty Acids” section.  Also, select the hyperlinks to “MCAD Deficiency” and “Refsum Disease” to study the associated content.
 
Studying this resource will take approximately1 hour to complete.
 
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  • Reading: The Medical Biochemistry Page: Michael W. King’s “Clinical Significance of Lipoprotein Metabolism” Link: The Medical Biochemistry Page: Michael W. King’s “Clinical Significance of Lipoprotein Metabolism” (HTML)
     
    Instruction: Please click on the link above, and study the “Clinical Significances of Lipoprotein Metabolism,” “Lipoprotein(a) and Atherogenesis,” and  “Pharmacologic Intervention” sections in their entirety.  Select the link to the “Aspirin Page” from the “Pharmacologic Intervention” section to read about associated content.  
     
    Studying this resource will take approximately 3hours and 30 minutes to complete.
     
    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.