This preview shows page 1-2-3 out of 8 pages.

View Full Document
View Full Document

End of preview. Want to read all 8 pages?

Upload your study docs or become a GradeBuddy member to access this document.

View Full Document
Unformatted text preview:

MCDB 310 1st Edition Lecture 12Outline of Last Lecture I. Chapter 10: Lipids II. Storage lipidsIII. Membrane lipidsIV. Non-storage/non-membrane lipidsOutline of Current Lecture I. Steroid HormonesII. VitaminsIII. Lab analysis of lipidsa. Column Chromatographyb. TLCc. Gas Liquid ChromatographyIV. Chapter 11: Biological membranesa. Fluid Mosaic Modelb. Proteins in membranesc. Lipids in membranesCurrent LectureI. Steroid Hormones: Messengers between tissuesa. Steroids are oxidized derivatives of sterols (sterol nucleus without an alkyl chain)b. Very active at low concentrationsc. They move throughout the blood stream (aqueous) as a complex with proteins (because on their own, steroids are hydrophobic)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. They bind to specific receptors with high affinity ii. Induce or inhibit gene expression and changes in metabolismiii. The receptors are not on the plasma membrane. The receptors are in the cytosol, and the receptor and hormone complex bind to the DNA together at the major grooved. Functions of steroid hormones:i. Gender hormonesii. Anti-inflammatory drugsiii. Treat asthma and arthritise. The structure of hormones are very similar, only small differences in the side chainsi. Exception: a few hormones have different kinds of rings II. Vitamins A and D: Hormone Precursorsa. Vitamin A (Retinol): on its own, it is not biologically activei. Derivatives are metabolic and cell regulators (retinoic acid regulates epithelial cell gene expression through nuclear receptors)ii. Retinal: a photosensitive pigment in rod and cone cells to produce a neuronal response (precursor to beta carotene)iii. Extremely non-polar, with rings on the ends that can be modified relatively easy (See structure below)1. Beta carotene  retinol cis-retinal  all trans retinal (biologically active)b. Vitamin E and K (very similar): redox cofactors and lipid quinones (free radical scavengers)i. A substituted aromatic ring + a long isoprenoid chainii. Very hydrophobic (associated with membranes and lipids dissolved in blood and lipid deposits)iii. Function: react with free radicals (like superoxide-can chew holes in otherstructures)iv. (See structure below) Red lines indicate isoprene subunits, and two rings at the end (one of which is a benzene ring), the electrons on the free radical will bind to the oxygen on the ringv. Vitamin K is very similar structurally, and it undergoes redox reactions as wellIII. Lab analysis of Lipidsa. Lipids are unlike proteins in physical properties, so they are studied in organic, non-polar solvents (non-aqueous solutions)b. In general, separation of mixtures of lipids utilizes differences in polarity and solubilityc. Lipid Extraction in organic solventsi. Take tissue and put it in a blender with a solution that is conducive to the lipids coming out of solution (usually a mixture of organic and non-organic solvents)ii. Usually use chloroform, methanol, and water which produces one phaseiii. Adding just a little more water separates it into two phases1. Water/methanol phase on top with proteins and sugars2. Organic phase on the bottomd. Adsorption Chromatography: Separation of lipids based on Polarity (column chromatography)i. Column is packed with insoluble polar material (silica)ii. Sample is added (polar lipids bind to the column, and neutral lipids do notbind to the column)iii. Column is washed with solvents increasing polarity (change it just a little bit at a time)1. Neutral lipids are eluted in the first wash (chloroform)2. Other lipids are eluted using solvents of increasing polarity3. Very polar or charged lipids are eluted with alcoholsiv. Lipids are eluted with they bind better to the solvent than to the non-polar columnv. Then, use mass spec. or IR spec. to analyze what we have elutede. Thin Layer Chromatographyi. Same principle as column chromatography except a plate of glass is coated with silica, the sample is applied as a spot of line to the bottom ofthe plate, and the bottom of the plate (up to the spot) is placed into the solventii. The solvent rises into the silica through capillary action (separating the lipids)iii. The lower the lipid affinity, the more the lipid moves (most soluble lipids move the most)iv. Lipids are detected with iodine vapors, fluorescence, or dyesv. Could still recover the spots off the platevi. This method ONLY separates the lipids, but you have no way of knowing ifthe lipids you have are pure or what the lipids aref. Two dimensional TLC: same method done twice, with two different solventsi. Put everything in one spot on the origin and put in solvent, so that the lipids migrate up the plateii. Result: appear to have several different lipids in the same spotiii. Turn plate on its side, and use a different solvent so that the lipids migratesideways across the plateiv. Result: all the lipids that can be separated will be separatedv. If we want to identify the lipids, we can run known standards1. Using the relationship of rise and run (2 different solvents) of the known standards, we can compare our unknowns to these knowns2. To make sure we have correctly identified the sample, we can scrape it off an run Mass spec. or IRg. Gas-Liquid Chromatography: separates charged lipids besti. Separates lipids based on solubilityii. Volatility in solvent: goes from liquid to gas states with increased temp1. Many lipids are naturally volatile2. Those that are not volatile must be derivatized in order to separate themiii. Inject lipids into “column” (wire) and add heativ. The lipids that go from liquid to gas first will be blown off by fans firstv. Retention time: how long the lipid stays in the column before it is blown offvi. Most of these machines have mass spec. machines at the end so that the lipids can be identified as they are blown offh. Lipids are then analyzed after they are separatedIV. Chapter 11: Applications for Chapters 3-10 (biological membranes and membrane transport)a. Membranes act as a selectively-permeable barrier for cells and organellesb. Molecular constituents of membranes (each type of membrane is built differently because of differing functions, but all have these components)i. Proteinii. Polar lipids:1. Implies that there are regulator controls on lipids synthesis, lipid transport, and membrane synthesisiii. Carbohydratesc. The distribution of membrane lipids


View Full Document
Loading Unlocking...
Login

Join to view Steroid Hormones and an introduction to Membranes and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Steroid Hormones and an introduction to Membranes and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?