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54 Cards in this Set
- Front
- Back
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What are some characteristics of lipids?
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-water insoluble
-Amphipathic -4th major molecule in body |
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What are the major Polar Lipids?
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fatty acids
cholesterol glycerophosphatides glycosphingolipids |
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What are the major Nonpolar lipids?
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-serve mainly as storage and transport
cholesteroyl esters Triacylglycerols |
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What fxns do Lipids perform?
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thermal insulation, energy storage (triacylglycerol), metabolic fuels, membrane components (phospholipids and cholesterol), hormones (steroids and vit D metabolites), precursors of prostanoids and leukotrienes, Vitamins A, D, E, K (c is water soluble), emulifying agents in the digestion and absorption of lipids, surfactants in the alveolar membrane, participation in the signal transduction pathways
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What are Fatty acids?
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carboxylic acids w/ long-chain hydrocarbon side groups
-hydrocarbons are hydrophobic and carboxylic acids are hydrophillic portion |
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How does the length of the hydrocarbon chain in Fatty acids affect its characteristics?
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-longer chains are more hydrophobic and have a higher melting point.
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How do double bonds affect Fatty acids?
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unsaturated - has double bonds
-lowers melting point -greater degree of fluidity in cell membrane |
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What is cervonic acid?
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Fatty acid w/ 6 double bonds
-found in membranes of retinal photoreceptors (need to be fluid) |
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What are triglycerides and their structure?
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storage form of FA - triacylglycerols
-3 FA covalently bonded to a glycerol molecule using ester bonds -FAs are usually mixed types - both in length and saturation --keeps it liquid |
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Where are triglycerides stored and what are they used for?
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kept in fat cells
-large amount of stored energy, source of heat insulation ---main lipid broken down to form acetyl-CoA - doesn't cause excessive ketone body production |
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How much more energy do tryglycerides have compared to glycogen?
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about 6 times the energy
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Does the eye store triglycerides?
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Not really, just a little to maintain membranes.
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What is the most important lipid class for the formation and maintenance of all forms of cellular membranes?
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phospholipids (phosphoglycerides)
-structure similar to triglycerides |
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How are phospholipids orientated in the cell membrane?
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charged/polar end points out to aqueous regions
nonpolar regions point towards the interior ---our lipid bilayer membrane |
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At what angle do the unsaturated chains bend?
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30 degrees
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How does the Fatty Acid composition of a phospholipid in membrane affect the functional needs of a cell?
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membrane fluidity
-RBCs - somewhat rigid to maintain biconcave disc shape ---tends to have shorter chain, unsaturated FA -Rod Outer Segments - require a high degree of membrane fluidity ---Cervonic acid (6 double bonds in the chain) |
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How much of the plasma membrane is made of sphingolipids and where can they be found in higher concentrations?
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10-20% of plasma membrane lipids
-myelin sheaths, brain (used in signal transduction) |
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What are gangliosides?
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complex sphingolipids used mainly for signal transduction.
-make up 6% of brain lipids |
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What are Isoprenoids?
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family of lipids built from 5-carbon units (isoprene)
-cholesterol, cortisol (steroids), lipid soluble vitamins (vit A), Coenzyme Q, variety of essential oils in plants (very common in plants) ---Isoprenoids are NOT structural components of membranes |
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What is the most abundant steroid in animals?
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cholesterol
-major component of plasma membranes 30-40% |
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What is the derivative of steroids?
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cyclopentanoperhydrophenanthrene - a compound of 4 fused, nonpolar cyclo alkane rings
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What is the shape of cholesterol?
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relatively flat and rigid
-adds rigidity into membranes |
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What are glucocorticoids and some fxns?
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steroid hormones - like cortisol
-affect carbohydrate, protein, and lipid metabolism -influence inflammatory rxns and the capacity to cope w/ stress |
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What is Aldosterone (mineralocorticoid) and some fxns?
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Steroid hormone
-regulate the excretion of salt and water by kidneys |
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What are Androgens and Estrogens?
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Steroid hormones
-affect sexual development and fxn |
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What is Addison's disease?
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Impaired adrenocortical fxn - causes hypoglycemia, muscle weakness, Na+ loss, K+ retention, impaired cardiac fxn, greatly increase susceptibility to stress
-can be caused by disease or trauma - treated w/ steroids |
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What is a Chalazion?
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a granulamatous inflammation of the eyelid margin assc w/ meibomian gland lipids
-lipids are high in cholesterol, a membrane lipid and not cholesteryl esters, which are the meibomian gland lipids |
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How do we get vit D and what is it used for?
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formed in the skin by photolytic action of UV light
active Vit D - increases serum [Ca++], increases deposition of Ca++ in bones and teeth deficiency: rickets in children |
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Where do we get Retinol (a form of vitamin A)?
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mainly plants - green vegetables, carrots, tomatoes
--beta-carotene |
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What is Retinal and what does it do?
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aldehyde converted form of Retinol
-fxns in the photoreceptor at low light intensities |
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What can a severe deficiency of Vitamin A do?
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lead to blindness
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What is Retinoic Acid?
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A derivative of Vitamin A
-hormone like properties stimulate tissue repair ---acne creams e.g. |
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Where does vit K come from?
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synthesized by plants and bacteria
- we get 1/2 our daily requirement from intestinal bacteria --we must ingest the rest |
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What is Vitamin K used for?
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involved in blood clotting
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What does a deficiency of vit K do?
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-inactive clotting proteins
-excessive bleeding ---Rat poison - warfarin - inactivates vit K |
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What is the polarity of Vit E and where is it found?
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highly hydrophobic
in cell membranes |
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What is the fxn of Vit E?
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antioxidant in membrane proteins and lipids
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What do vit E supplements do?
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protect against oxidative damage to cells
reduces the effects of aging |
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What are eicosanoids?
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cyclic lipids derived from eicosanoic acids (like arachidonic acid)
-prostaglandins -thromboxanes -Leukotrienes |
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How do eicosanoids fxn?
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-in very low concentrations
-as local, short acting hormones |
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What are the fxns of eicosanoids?
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-production of pain and fever
-regulation of BP -regulation of blood coagulation and reproduction |
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What is a Micelle in the Lipid Bilayer?
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a globular aggregate whose hydrocarbon groups are out of contact w/ water
-pretty much forms a sphere w/ the tails pointing in and the heads pointing out |
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What are Liposomes in the lipid bilayer?
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closed, self sealing solvent filled vesicles that are bound only by a single bilayer
--has a space in the middle |
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What is transverse diffusion or flip-flopping in lipid bilayer?
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a lipid tries to go from one side of the bilayer to the other
-rare, slow, hydrated-polar head has to pass through the hydrophobic hydrocarbon core |
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What is lateral diffusion in the lipid bilayer?
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movement of lipids laterally on the same side of the bilayer
-fast |
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What does cholesterol provide in the bilayer?
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decreases membrane fluidity
broadens temp range of phase transition membrane plasticizer - pliable |
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What do membrane proteins do in the lipid bilayer?
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catalyze chemical rxns
mediate flow of nutrients and waste across the membrane relay information |
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What are the 3 types of membrane proteins?
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Integral
Lipid-linked Peripheral |
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What are Integral membrane proteins?
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Transmembrane proteins - completely span membrane
-good b/c bypasses all the different charges of membrane |
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What are Lipid-Linked proteins?
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membrane proteins covalently anchored to lipids
-harder to remove than Peripheral membrane proteins |
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What are peripheral membrane proteins (cytochrome c)?
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surface proteins that are loosely bound to lipid membrane
-easy to remove - high ionic strength salts, pH changes |
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How does the Fluid Mosaic Model pertain to integral proteins?
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integral proteins are visualized as "icebergs" floating in a 2D lipid "sea" in a random or mosaic distribution.
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Can integral proteins diffuse laterally in the membrane?
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Yes, unless other cell components restrict their movement
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Are membranes symmetrical on the 2 sides?
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NO - inner has slightly more total phospholipids than inner
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