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41 Cards in this Set
- Front
- Back
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What is a general definition of Lipids?
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Defined by Solubility, not structures (unlike carbs, proteins, NA)
heterogeneous organic (diethyl ether, acetone, dichloromethane) insoluble in water soluble in non polar |
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What are some functions of Lipids?
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Storage of energy - 9 kcal/gram compared to 4 for carbs, efficient
ex. triglycerides Membrane components - hydrophobic, provide membranes that separate aqueous compartments ex. complex lipids, cholesterol Messengers - 1: signals from one part of body to another, ex. steroid hormones 2: mediate local hormone response, ex. prostaglandins |
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What are some structural classifications of lipids?
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Simple: esters of fatty acids w/ glycerol
ex. triglyceride = 3 FA + Glycerol Complex: simple + non lipid ex. phospholipids, glycolipids Steroids: cholesterol and hormones Derived Lipids: prostaglandins, leukotrienes, thromboxanes |
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What is a Fatty Acid and some important ones?
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Hydrophobic hydrocarbon chain + hydrophillic carboxyl group: CH3(CH2)n COO-
Butyric and Capric Acid - FA w/ chain lengths of 4-10 C are found in milk Palmitic Acid - structural lipids and triacylglycerols contain primary FA of at least 16 C Linoleic & Linolenic Acid - examples of PUFA, Essential fatty acids (must be obtained from diet), humans can synthesize saturated and mono-unsaturated FA Arachidonic Acid - precursor of prostaglandins |
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What is a Triglyceride?
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also called triacylglycerol
major component of human diet & most abundant lipid in plant and animal cells contain even number C (10-20) [hydrophobic] because built from acetate (2C) only have COOH group, no other function group but some have double bond, 2-3 types FA present cis predominates |
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What are the physical state properties of triglycerides?
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inc # C, dec double bond, inc MP
FATS: saturated FA -semisolid or solid at RT -animal fats OILS: unsaturated FA -liquid at RT -vegetable oils Pure fats and oils are colorless, odorless, and tasteless saturated lie parallel, stronger forces, inc MP unsaturated less ordered, weaker, low MP |
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What is Hydrogenation of Triglycerides?
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hardening of lipids
reduction of double bonds using H2 and catalyst ex. fats for kitchen, margarine |
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What is Saponification of Triglycerides?
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hydrolysis using a base produces glycerol and FA salts called soaps
TG + 3NaOH --> Glycerol + 3 R Coo Na (soap) |
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What is rancidity of lipids?
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decomposition due to oxidation, leading to foul taste and odors
double bonds in fats and oils are subject to oxidation by air hydrolysis of TG may produce short chain FA, such as butyric acid, producing bad smells prevention: refrigeration, dark containers, antioxidants |
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What are waxes?
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contains variety of long-chain alkanes, esters, polyesters of long chain alcohols and FAs
soild due to high MW higher melting points than Fats ex. animal and plant waxs, provide protective coatings, bee wax, feathers of birds used to make cosmetics, polishes, candles, and ointments |
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What are Phospholipids?
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complex lipids, main components of membranes
contains alcohol, FA, and a phosphate ester glycerophospholipid - alcohol is glycerol sphinogolipid - alcohol is sphingosine Glycolipids: alcohol is sphingosine and contains a carbohydrate |
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What is a Glycerophospholipid?
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also called phosphoglycerides
2nd most abundant of naturally occurring lipids found exclusively in membranes, 40-50 % GPL and 50-60 % proteins |
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What is the structure of Glycerophospholipid and some common GPLs?
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similar structure to triglyceride
most abundant derived from phosphatidic acid (glycerol esterified by 2 FA and 1 H3PO4) alcohol = glycerol C1 - usually SFA C2 - always UFA C3 - phosphate group 3 most abundant FA in phosphatidic acid are Palmitic, stearic, and oleic Varioud GPLs: Phosphatidylcholine (Lecithin) - egg yolk, yellow-brownish occurring in animal and plant tissues Phosphatidylethanolamine (Cephalin) - membrane component Phosphatidylserine (Cephalin) - membrane component Phosphatidylinositol - membrane component, chemical communications |
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What are Sphingolipids?
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alcohol is sphingosine
Ceramide = sphingosine + FA, component of cerbrosides in NT sphigomyelin - Ceramide + Phosphocholine, component of myelin, coating of nerve axons |
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What are Glycolipids?
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Glycolipid = ceramide + carbohydrates (glucose or galactose)
cerebroside - ceramide + mono/oligosaccharide, impt component of NT, 7 % of brain's dry weight ganglioside - ceramide + complex oligosaccharide, cellular recognition and communication |
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What are some Lipid Storage Diseases?
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Gaucher's disease:
accumulated lipid - glucocerebroside missing enzyme - Beta glucosidase Krabbe's Leukodystrophy: accumulated lipid - galactocerbroside missing enzyme - beta galactosidase Fabry's disease: accumulated lipid - ceramide trihexoside missing enzyme - alpha galactosidase Tay-Sach's disease: accumulated lipid - ganglioside (ceramic oligosaccharide) missing enzyme - hexosaminidase A Niemann-Pick disease: accumulated lipid - sphigomyelin missing enzyme - shingomyelinase |
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What are properties of lipid solubility?
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amphipathic - hydrophillic and hydrophobic
can be arranged in mono or bilayer, or micelle membranes are made up of lipids, proteins, and few carbs complex lipids play important role in structure and function of membranes (highly selective permeability) |
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What are some features of membrane structure?
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hydrophillic head, hydrophobic tail
hydrocarbon tail can be rigid (rich in saturated FA) or fluid (rich in UFA) |
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What is the fluid Mosaic Model?
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Fluidity:
-UFAs prevent tight packing -helps in endo and exo cytosis Mosaic: -because proteins dispersed in lipid bilayer |
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What are the types of membrane transport?
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permeability determined by:
-lipid solubility -molecular size Simple diffusion: Carrier required - No With or Against gradient? With Energy Required? No Examples - Gases, water Facilitated Diffusion: Carrier required - Yes With/Against conc. gradient? With Energy required? No Examples - glucose transporters Primary Active: Carrier required? Yes With/Against gradient? Against Energy required? Yes, directly Example - Sodium/Potassium ATPase Secondary Active: Carrier required? Yes With/Against conc. gradient? Against Energy required? Yes, indrectly Example - glucose absorption Ion Channels: Carrier required? Yes WIth/Against conc. gradient? Both Energy required? No Example - Sodium and Calcium channels |
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What are steroids?
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compounds having a tetracyclic ring structure
3 cyclohexane rings are connected in same way as Phenanthrene fused cyclopentane ring is also present the 4 rings combined make up the "steroid nucleus" include: cholesterol, hormones, bile salts |
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What is Cholesterol?
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most abundant steroid in body
function: -structural component in cell membranes -synthesis of steroid hormones (corticosteroid and sex hormones), bile salts, and Vit D exists in: -free form or esterified with FA high serum level is associated with atherosclerosis need water-soluble carrier (lipoproteins) |
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What are Lipoproteins?
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transport cholesterol and fats
spherically shaped clusters containing lipids and protein molecules contain: -core of hydrophobic lipid molecules surrounded by hydrophilic molecules such as proteins and phospholipids classified in 4 types: HDL LDL VLDL chylomicrons |
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What is HMG-CoA reductase?
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synthesizes cholesterol, blocked by statin drugs to provent accumulation of cholesterol in plasma
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How are steroid hormones formed?
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cholesterol loses a 6C unit, and alcohol of carbon 3 is oxidized to a ketone: C27 --> C21 (progesterone)
forming progesterone, starting compound for sex (testosterone and estradiol) and adrenocorticoid hormones (cortisol and aldosterone) |
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What are the Adrenocortcoid hormones?
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secreted from adrenal cortex
aldosterone - one of minerolocorticoids. retains Na and Cl, eliminates K Cortisol - major glucocorticoid, control carbohydrate metabolism, antiinflammatory, increase synthesis of glucose and glycogen Cortisone - antiinflammatory |
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What are the Sex Hormones?
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testosterone - male sex hormone, anabolic steroids abused by athletes mimic effects of testosterone
estradiol - female sex hormone, along with progesterone regulate menstrual cycle progesterone - prepares uterus for implantation, syntehtic progesterone compounds (norethindone and mifepristone) used in oral contraceptives |
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What are Bile Salts and what is Emulsification?
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Emulsification: Dispersion and increasing the surface area of lipids
oxidation products of cholesterol ex. glycocholate (contains glycine), taurocholate (contains Taurine[cysteine derivate]) synthesized in liver, stored in galbladder, secreted in intestine powerful detergents and emulsify fats |
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What is Vitamin D?
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synthesized in skin from cholesterol
calcitrol function in calcium metabolism deficiency: rickets in children, osteomalacia in adults |
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What are Prostaglandins?
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example of derived lipid
family of compounds that have the 20C skeleton of prostanoic acid synthesized from membrane-bound arachidonic acids in response to specific physiological triggers catalyzing enzyme of COX (cyclooxygenase) COX-1: production of PG in normal conditions COX-2: production of PG in inflammation |
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What are some important features of prostaglandins (PG) biologically?
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cause constriction or dilation of smooth muscles
cause aggregation or disaggregation of platelets sensitize spinal neurons to pain regulate inflammatory reactions control hormone regulation |
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What are examples of NSAIDs?
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antipyretic and inhibit synthesis of prostaglandins
celecoxib Voltaren and Celebrex |
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What are Thromboxanes?
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derived from arachidonic acid
thromboxane A2 induces platelet aggregation and vasoconstriction aspirin and other NSAID prevent syntehsis of thromboxanes by inhibiting COX enzyme aspirin is used to prevent heart attacks, strokes, and blood clot formation |
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What are Leukotrienes?
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also synthesized from arachidonic acid
occur in leukocytes associated with immune system cause asthma-like attacks, lasting muscle contractions recently-developed anti-asthma drugs inhibit synthesis of leukotrienes |
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What are the functions of Chylomicrons, their apoproteins and functions?
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transport dietary triglyceride and cholesterol from intestine to tissues
Apoproteins: apoB-48 - secreted by epithelial cells apoC-II - activates lipoprotein lipase (LPL) which hydrolyze tryglyceride in chylomicron apoE - uptake by liver |
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What is the function of VLDL, their apoproteins and functions?
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transports trigylcerides that are newly synthesized or retrieved from the chylomicron remnants from liver to tissues
Apoproteins: apoB-100 - secreted by liver (uptake of LDL) apoC-II - activates LPL apoE - uptake of remnants by liver |
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What is the function of LDL, their apoproteins and functions?
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delivers cholesterol into cells
Apoproteins: apoB-100 - uptake by liver and other tissues via LDL receptor (apoB-100 receptor) |
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What is the function of IDL (VLDL remnants), their apoproteins and functions?
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-picks up cholesterol from HDL to become LDL, picked up by liver
-transfer of cholesteryl esters is carried by cholesterol ester transfer proteins (CETP) Apoproteins: apoE - uptake by liver |
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What is the function of HDL, their apoproteins and functions?
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-picks up cholesterol accumulating in blood vessels
-delivers cholesterol to liver and steroidogenic tissues via scavenger receptor (SR-B1) -shuttles apoC-II and apoE in blood Apoproteins: apoA-I - activates lecithin cholesterol acyltransferase (LCAT) to produce cholesterol esters |
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What are the major roles of each apoproteins?
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Apo A:
-activator of LCAT which converts free cholesterol to cholesteryl ester in HDL (reverse cholesterol transport) Apo B: -required for receptor-lipoprotein interaction for lipoprotein uptake -Apo B-48(from intestine) - uptake of chylomicron remnant by liver cells -Apo B-100(from Liver) - uptake of LDL by peripheral tissues (20%) or liver cell (80 %) Apo C: -activator of LPL which hydrolyzes lipids (mainly TG) in lipoproteins, such as Chylomicrons and VLDL Apo E: -required for receptor-lipoprotein interaction for lipoprotein uptake |
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What are Apolipoproteins functions?
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provide recognition sites for cell-surface receptors
activators or coenzymes of enzymes Ex.. Apo A, B, C, E |
