LAB Exp 6. Lipids Flashcards
T/F: lipids are water soluble; they are nonpolar
T;F
T/F: lipids are soluble to organic solvents
T
Examples of organic solvents where lipids are soluble
Diethyl ether
Dichloromethane
Acetone
Building block of complex lipids
Fatty acyls
Long-chain monocarboxylic acids
Fatty acids
Long hydrophobic tail and a polar head
Fatty acids
Fatty acids differ in terms of (3)
Degree of unsaturation
Length of HC tails
Position of double bonds
Identify whether saturated or unsaturated fatty acid: contains only single C-C bonds
Saturated
Identify whether saturated or unsaturated fatty acid: CnH2n+1COOH
Saturated
Identify whether saturated or unsaturated fatty acid: without C=C bond
Saturated
Identify whether saturated or unsaturated fatty acid: waxy solids at RT
Saturated
Identify whether saturated or unsaturated fatty acid: animal fats
Saturated
Identify whether saturated or unsaturated fatty acid: high melting points
Saturated
Identify whether saturated or unsaturated fatty acid: contains one or more C=C bonds
Unsaturated
Identify whether saturated or unsaturated fatty acid: CnH2n-1, CnH2n-3COOH, CnH2n-5COOH
Unsaturated
Identify whether saturated or unsaturated fatty acid: liquids at RT
Unsaturated
Identify whether saturated or unsaturated fatty acid: vegetable fats
Unsaturated
Identify whether saturated or unsaturated fatty acid: low melting points
Unsaturated
T/F: naturally occurring unsaturated fats have trans- orientation
F
Where does the bend insert in unsaturated fatty acids?
HC chain
The higher the number of carbons, the ____ the melting point
Higher
In the case of same number of carbon atoms, the higher the number of double bonds, the _____ the melting point
Lower
A group of signal lipids
Eicosanoids
Derived from the metabolism of arachidonic acid by the enzyme cyclooxygenase (COX)
Eicosanoids
Derived mainly from arachidonic acid
Protaglandins
Have a variety of potent biological activities of hormonal or regulatory nature
Prostaglandins
Parent compound is prostanoic acid
Prostaglandins
Control blood pressure
Prostaglandins
Stimulate muscle contration
Prostaglandins
Inhibit platelet aggregation
Prostaglandins
Induce inflammation
Prostaglandins
Induces platelet aggregation and vasoconstriction
Thromboxane A
Aspirin and other NSAIDs inhibit the synthesis of _____
Thromboxanes
T/F: leukotrienes are synthesized from arachidonic acid
Leukotrienes
Leukotrienes as _____ double bonds
3
Produce muscle contractions, especially in the lungs and thereby can cause asthma-like attacks
Leukotrienes
T/F: leukotrienes are 20 times more potent than histamine
F (100 times)
Comprise the bulk of storage fat
Glycerolipids
A type of glycerolipid formed by esterification of three fatty acids to glycerol
Triacylglycerol
T/F: triacylglycerol is also known as neutral lipid
T
Reaction of a TAG with a base producing glycerol and three molecules of fatty acids
Saponification
Most abundant lipid in most membrance
Phosphoacylglycerol
Have polar head and two nonpolar tails
Phosphoacylglycerol
Control cell permeability
Phosphoacylglycerol
Other term for phosphatidylcholine
Lecithin
Abundant in brain and nerve tissue
Phosphatidylcholine (lecithin)
Found in egg yolk, wheat germ, yeast
Phosphatidylcholine (lecithin)
Other term of phosphatidylethanolamine
Cephalin
Other term for diphosphatidylglycerol
Cardiolipin
The only antigenic lipid so far
Cardiolipin/diphosphatidylglycerol
The second large class of membrane lipids
Sphingolipids
Abundant in nervous system
Sphingolipids
Sphingomyelin contain _____ or _____ as their polar head
phosphocholine or phosphoethanolamine
Sphingomyelin is most commonly found in _____
Myelin sheath
A carbohydrate is bound to an alcohol group of a lipid by a glycosidic linkage
Glygolipids
“sterol alcohols”
Sterol lipids
Signals molecules located along the membrane
Sterol lipids
Contains aromatic alcohol which are derivatives of steroid nucleus
Steroids
Steroids has ____ cyclohexane rings and ___ cyclopentane ring
3, 1
Precursor for the synthesis of other steroids
Cholesterol
Derived from squalene
Cholesterol
A C30 terpenoid HC
Squalene
T/F: cholesterol is strongly amphipathic
F (weakly amphipatic)
T/F: cholesteryl esters are non-hydrolyzable
F
Terpenes, carotenoids, quinones, hydroquinone are examples of ___
Prenol lipids
Identify the prenol lipid: isoprene derived natural metabolite
Terpenes
Identify the prenol lipid: insect and plant growth hormone
Terpenes
Identify the prenol lipid: plant’s pleasant odors
Terpenes
Identify the prenol lipid: lipid-like sugar carriers
Terpenes
Fatty acid with a sugar backbone
Saccharolipid
Has glucosamine precursoe
Saccharolipid
Secondary metabolites of living organisms for survival
Polyketides
Used as anti-microbial, anti-parasitic, and anti-cancer
Polyketides
Doxycycline and aflatoxin are examples of _____
Polyketides
Esters of fatty acids with long chain alcohols
Waxes
Enumerate the saponifiable lipids (with fatty acids)
TAGs
Sphingolipids
Waxes
Phosphoacylglycerols
Glycolipids
Enumerate the non-saponifiable lipids (without fatty acids)
Steroids
Terpenes
Prostaglandins
Leukotrienes
Thromboxanes
What are the fat-soluble vitamins?
A, D, E, K
Identify the fat-soluble vitamin: an isoprenoid alcohol that plays a key role in vision
A
Identify the fat-soluble vitamin: control of animal growth
A
Identify the fat-soluble vitamin: stimulation of development of nervous system
A
Identify the fat-soluble vitamin: can either be consumed in diet or biosynthesize from b-carotene
A
Enumerate some examples of Vitamin A sources
cod liver oil, fish livers, butter, eggs
Identify the fat-soluble vitamin: regulation of Ca & P metabolism
D
Identify the fat-soluble vitamin: deficiency leads to ricketsia
D
Identify the fat-soluble vitamin: can also be found in cod liver oil and dairy products
D
The most abundant form of Vitamin D is ____
D3 (Cholecalciferol)
Identify the fat-soluble vitamin: has an antioxidant role
E
Identify the fat-soluble vitamin: prevents attack of peroxides on unsaturated fatty acids in membrane lipids
E
Identify the fat-soluble vitamin: found in eggs & vegetable oils
E
Enumerate the common sources of Vitamin E
corn, peanut, wheat germ
Other term Vitamin E
a-tocopherol
Identify the fat-soluble vitamin: deficiency leads to muscular dystrophy
E
Identify the fat-soluble vitamin: deficiency leads creatinuria
E
Identify the fat-soluble vitamin: deficiency leads to anemia
E
Identify the fat-soluble vitamin: important in the lymphatic synthesis of prothrombin & protein factors in blood platelets
K
Identify the fat-soluble vitamin: Vitamin K found in animals & bacteria
Vitamin K2 (menaquinone)
Identify the fat-soluble vitamin: Vitamin K found in plants
Vitamin K1 (phylloquinone)
Identify the fat-soluble vitamin: deficiency leads to diminished intestinal absorption of lipids
K
Identify the reagent for isolation of lipids: denatures the proteins and disrupts the lipoprotein complexes of the egg yolk
Ethanol
Identify the reagent for isolation of lipids: used to remove neutral or least polar lipids
Hexane
Identify the reagent for isolation of lipids: provides mild hydration condition
Acetone
Identify the reagent for isolation of lipids: the H2O content decreases and extracts the fatty acids, sterol, and other simple lipids
Acetone
Identify the reagent for isolation of lipids: the remaining polar lipids with some neutral lipids are further precipitated
Acetone
Stationary phase in column chromatography
Silica gel
Enumerate the mobile phase in column chromatography
- petroleum ether: ethyl ether (9:1) - least polar
- 5% MeOH in DCM
- DCM:MeOH:H2O (1:3:1) - most polar
Describe the result of the first eluate in ester test
Deep burgundy (++); due to fatty acids of TAG
Describe the result of the second eluate in ester test
Deep burgundy (+/-); due to cholesterol ester
Describe the result of the third eluate in ester test
Deep burgundy (-); due to fatty acids of sphingolipids or phosphoacylglycerol
Describe the result of the first eluate in glycerol test
Burnt fat odor (++); presence of glycerol
Describe the result of the second eluate in glycerol test
(-)
Describe the result of the third eluate in glycerol test
Burnt fat odor (+); presence of glycerol
Describe the result of the first eluate in liebermann-burchard test
(-)
Describe the result of the second eluate in liebermann-burchard test
Emerald green (+); due to cholesterol
Describe the result of the third eluate in liebermann-burchard test
(-)
Stationary phase of TLC in lipids
Silica G-250
Enumerate the reagents for TLC in lipids
- Petroleum ether: methanol: H2O (65:25:4)
- Petroleum ether: methanol: NH4OH (65:25:4)
Enumerate the visualizing agents of TLC in lipids
I2
Ninhydrin
This visualizing agent appears as yellow-brown spots
I2; due to oxidation of unsaturated fatty acids
This visualizing agent appears as blue-violet spots
Ninhydrin; due to free amino groups
Enumerate the standards for TLC in lipids
cholesterol, lecithin
Purpose of hydroxamic test
Detects the presence of carboxylic acid ester (TAGs, glycerophospholipids, cholesteryl esters)
Reagents for hydroxamic test
ethanol:buthanol (3:1); NH2OH x HCl;
NaOH;
FeCl3;
HCl
Positive result for hydroxamic test
Burgundy color
Principle of hydroxamic test
Complexation reaction
Purpose of acrolein test
Detects the presence of glycerol (TAGs, glycerophospholipids)
Positive result for acrolein test
Burnt fat odor
Reagent for acrolein test
KHSO4, water bath
Principle involved in acrolein test
dehydration and oxidation
Purpose of liebermann-burchard test
Detects the presence of unsaturated sterols (cholesterol)
Reagents for liebermann-burchard test
Conc. H2SO4, acetic anhydride
Positive result for liebermann-burchard test
Emerald green solution
Principle involved in liebermann-burchard test
Esterification of OH at C-3 with acetic anhydride and epimerization of double bond at C-5
Purpose of kraut’s test
Detects the presence of choline (phosphatidyl choline, sphingolipids)
Reagents for kraut’s test
Bismuth nitrate, 3M HNO3, KI (Kraut’s reagent)
Positive result for kraut’s test
Dark orange to red ppt
Principle involved in kraut’s test
Complexation reaction
Proposed condensation, dehydration, and epimerization
Modification of Dragendorff’s test
A test for alkaloids
Dragendorff’s test
Purpose for Ascorbic acid method
Detects the presence of phosphate (phospholipids)
Reagents for Ascorbic acid method
6M HNO3, 6M NaOH, Molybdate reagent, 0.1M Ascorbic acid solution
Principle of ascorbic acid method
Ammonium molybdate and pottasium antimonyl tartrate react in acid medium with orthophosphate to form a heteropoly acid - phosphomolybdic acid - that is reduced to intensely colored molybdenum blue by ascorbic acid
Purpose of ninhydrin test
Detects the presence of a-amino group
Reagents for ninhydrin test
Triketohydrindene hydrate (ninhydrin in EtOH)
Positive result for ninhydrin test
Blue-violet solution
Principle of ninhydrin test
Oxidative deamination followed by condensation
Purpose of bromine/iodine test
Detects the presence of double bonds; degree of unsaturation
Reagents for test for lipid unsaturation
5% bromine / iodine solution
Positive result for bromine/iodine test
Loss of reddish brown color - Iodine
Loss of violet coloration - bromine
Identify the lipid index: number of mg of KOH required to saponify the free and combined fatty acids in 1g of a given fat
Saponification number
Identify the lipid index: indicates the molecular weight and is inversely proportional to it
Saponification number
Identify the lipid index: Number of grams of iodine absorbed by 100mg of fat
Iodine number
Identify the lipid index: a measure of degree of unsaturation of a fat
Iodine number
Identify the lipid index: number of mg of KOH required to neutralize the fatty acids in a gram of a fat
Acid number
Identify the lipid index: indicates the degree of rancidity of a fat
Acid number
An additional test for lipids that detect the presence of sugar moiety
Molisch test
Reagents for molisch test
1% ethanolic a-naphthol, conc H2SO4
Positive result for molisch test
Violet ring at the interface
Principle involved in molisch test
Hydrolysis, dehydration, and condensation reaction
Molisch test is positive for ____ and _____
Cerebrosides and gangliosides
