Ch9-120222 - CHEM 350: Introduction to Biological Chemistry...

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Unformatted text preview: CHEM 350: Introduction to Biological Chemistry Brian Lee, Ph.D. brianlee@siu.edu Office: Neckers 146G or 324 Phone: 453-7186 Ho urs: 9:30am to 10:30am or by appointment Website: https:/ /online.siu.edu Textbook (required, U.S. edition only) Fundamentals of Biochemistry, 3rd Ed., Voet, Voet & Pratt. Study Guide (recommended) Student Companion to Fundamentals of Biochemistry, 3rd Ed. Help Desk Tuesday 6:30 to 7:30 pm in Neckers 218 Thursday 5:00 to 6:00 pm in Neckers 410 Announcements Undergraduate Research Opportunities Research for credit (such as CHEM 396 or CHEM 496) Student worker ($8.00 per hour) (http://www.siu.edu/~fao/jobs/) Undergraduate Assistantships (http://www.siu.edu/~fao/jobs/) McNair Scholars Program (http://www.siu.edu/~mcnair) REACH Awards Competition (http://www.siu.edu/~reach/) Summer Research Experiences for Undergraduates (REU) Deadline for SIUC REU Program is March 7th For other REU programs, search the National Science Foundation site: http://www.nsf.gov/crssprgm/reu/index.jsp Students must contact the individual sites for information and application materials. NSF does not have application materials and does not select student participants. A contact person and contact information is listed for each site. Assignments Read Chapter 9 Lipids and Biological Membranes Chapter 9 Problems Student Companion site for Voet, Voet & Pratt http://bcs.wiley.com/he-bcs/Books?action=index&bcsId=4274&itemId=0470129301 Second Midterm Exam, Wednesday February 29th Chapters 6 through 9 (All exams are cumulative) No class on Monday, February 27th (no office hours) Help Desk Tuesday 6:30 to 7:30 pm in Neckers 218 Thursday 5:00 to 6:00 pm in Neckers 410 Structural Lipids in Biological Membranes - glycerophospholipids - sphingolipids (phospholipid and glycolipid forms) - galactolipids and sulfolipids - ether lipids - sterols Structural lipids share a general chemical structure: three carbon backbone, fatty acid residues, polar head group Triacylglycerols (triglycerides, fats, neutral fats) Fatty acid esters of glycerol. Provide energy storage and insulation (adipose tissue). Glycolipids – two fatty acid tails and a sugar residue. Phospholipids Major component of biological membranes. Amphipathic with non-polar “tails” and polar “heads” Glycerophospholipids Phospholipids The fatty acid “tails” determine the membrane fluidity. The polar “head” groups interact favorably with solvent. The polar “head” groups dictate how membranes interact with the environment. Glycerophospholipids Glycolipids Phospholipids Major component of biological membranes. Amphipathic with non-polar “tails” and polar “heads” Glycerophospholipids Phospholipids The fatty acid “tails” determine the membrane fluidity. The polar “head” groups interact favorably with solvent. The polar “head” groups dictate how membranes interact with the environment. Glycerophospholipids Phospholipids cis- 9 or -9 for oleic acid 30° bend in chain for cis What are trans fats? -fatty acid containing trans double bonds -straight chain conformation (higher melting point) -fatty acid metabolism prefers cis double bonds Where do trans fats originate? -partial hydrogenation of unsaturated fatty acids -developed in early 1900’s to create CriscoTM -use polyunsaturated vegetable fats - double bonds increase risk of oxidation (rancid) -hydrogenates double bonds -> single bonds -partial hydrogenation also creates trans double bonds Do trans fats occur in nature? -rarely. Only found in the rumen of cows, etc. Phospholipids: Ether lipids plasmalogen - heart tissue note: vinyl ether linkage is easily hydrolyzed by oxygen free radicals, prevents further damage. inflammation and allergic response Archaebacteria have uniquely specialized structural lipids to survive extreme conditions. -ether linkages -branched hydrocarbons -long chain tetraethers glycerol dialkyl glycerol tetraethers (GDGTs) Sphingolipids Major component of biological membranes, especially important for nerve cells. Derivatives of C18 amino alcohol, sphingosine which includes a long hydrocarbon chain with trans double bond. Only one fatty acid is attached through an amide bond. The remaining alcohol is attached to a phospho-alcohol group, just as other phosphlipids, or directly through a glycosidic bond to a sugar moiety. glycosphingolipids cerebrosides globosides gangliosides Sphingomyelin A major component of the myelin sheath in nerve cells Sphingomyelins resemble phosphatidylcholines in their general properties and three-dimensional structure. Both have similar roles in the structure of cellular membranes. Cerebroside is one of the simplest glycolipids based on sphingosine with a glucose or galactose attached directly through a glycosidic bond (no phosphodiester linkeage) The ß-D-galactose head group is most prevalent in the membrane of brain cells. Both are neutral glycolipids. GM - mono-sialic acid (-1) GD - di-sialic acid (-2) GT - tri-sialic acid (-3) Gangliosides are complex glycolipids, prevalent in brain cells. Recognition of extracellular molecules and other cells. Receptors for pituitary hormones and cholera toxin. Glycosphingolipids and glycoproteins are major determinants of ABO blood groups through display of antigenic oligosaccharides on the cell surface. Individuals produce antibodies against the A antigen if they have B or O antigenic oligosaccharides (blood type). Individuals produce antibodies against the B antigen if they have A or O antigenic oligosaccharides (blood type). Phospholipids and sphingolipids are degraded in lysosomes. Genetic deficiency in any lysosomal enzyme leads to an excess of a partially degraded sphingolipid which can cause disease, such as Tay-Sachs. Cholesterol is the most prevalent steroid. Weakly amphipathic and very rigid due to ring structure. Steroids are almost exclusively found in eukaryotic cells and constitutes 25% of blood and brain cell membranes. Phospholipases A1 and A2 hydrolyze the ester bonds of intact glycerophopholipids at C-1 and C-2 glycerol. Phospholipases C and D split phosphodiester bonds in the headgroup Lipids as signals, cofactors and pigments. Phosphatidylinositols are involved in cellular regulation. Lipids as Hormones: Intercellular Messengers Eicosanoids: act locally in cells near the point of synthesis. prostaglandins -fever and pain thromboxane: -blood clotting leukotrienes: -anaphylactic shock arachidonic acid: an -6 fatty acid NSAIDs = nonsteroidal anti-inflammatory drugs Prostagladin H2 synthase or cyclooxygenase (COX-2) promotes the inflammatory response to infections leading to high fevers. Aspirin is an irreversible inhibitor. The acetyl group of aspirin is transferred to the protein and blocks the hydrophobic channel for substrate binding. COX-2 is inducible and associated with macrophages Lipids as Hormones: Intercellular Messengers Steroids are carried by the bloodstream to distant tissues to regulate metabolism, inflammation, kidney function, and reproductive development. As oxidized derivatives of sterols, steroids are more polar than cholesterol and bind to receptors on the membrane surface. Steroid drugs have an anti-inflammatory effect by inhibiting phospholipase activity and reducing prostagladin synthesis. Vitamin D production and metabolism Photolytic action of UV light Vitamin D regulates metabolism in kidneys, bones and intestines. Rickets Vitamin D deficiency reduces uptake of Ca2+ from intestines. Vitamin D toxicity Excess vitamin D leads to high Ca2+ serum levels causing calcification and kidney stones. ...
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This note was uploaded on 03/26/2012 for the course CHEM 350 taught by Professor Lee during the Spring '08 term at SIU Carbondale.

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