Lipids Flashcards
Lipids are a family of substances that are ____ in water but ____ in nonpolar and low polarity solvents such as diethyl ether, acetone, and DCM.
soluble or insoluble
insoluble; soluble
A fatty acid has a long and unbranched ____ chain.
carbon chain
or hydrocarbon chain
this accounts for the lipids’ insolubility in water
A fatty acid has a ____ group at one end that is usually ionized and accounts for the hydrophilic nature of the molecule
carboxyl group
ionized = COO-
In the notation 16:1 of Palmitoleic acid, what does 16 and 1 signify?
- 16 = # of carbons
- 1 = # of double bonds
kapag may triangle: ex: 16:1∆9, the 9 tells us that the double bond is found at the 9th carbon starting from the carboxyl end of the molecule
Characteristics of fatty acids
Nearly all fatty acids have an ____ number of carbon atoms, most between 12 and 20, in an unbranched chain.
odd or even
even
Characteristics of fatty acids
What are the three most abundant fatty acids in nature?
- palmitic acid
- stearic acid
- oleic acid
16:0; 18:0; 18:1
Characteristics of fatty acids
In most unsaturated fatty acids, what isomer predominates?
cis isomer
trans is rare
Characteristics of fatty acids
Unsaturated fatty acids have ____ melting points than their saturated counterparts
higher or lower
lower
Characteristics of fatty acids
The ____ the degree of unsaturation, the lower the melting point
greater or lower
greater
What type of fatty acids only have single bonds in their hydrocarbon chains?
Saturated fatty acids
What type of fatty acids have double bonds in their hydrocarbon chains?
Unsaturated fatty acids
Saturated fatty acids are ____ at room temperature
solid or liquid
solid
because the regular nature of their hydrocarbon chains allows their molecules to pack together in a close parallel alignment
Unsaturated fatty acids are ____ at room temperature
solid or liquid
liquid
because the C=C double bonds create bends in the carbon chain, making it harder for fatty acids to pack together tightly.
True or False
The longer the hydrocarbon chain is, the more energy the energy is needed to separate and melt them
True
True or False
The double bonds present in unsaturated fatty acids inserts a bend in the hydrocarbon chain
True
Plant oils are liquid at room temperature because they have higher proportions of ____ fatty acids than do animal fats, which tend to be solids
saturated or unsaturated
unsaturated fatty acids
____ are triesters of glycerol and fatty acids.
Triglycerides
ester = R-O-(C=O)-R
What do you call the alcohol portion of triglycerides?
glycerol
What is the acid component of triglycerides?
fatty acids
Are triglycerides soluble in water or no?
no.
Although the ester groups are polar, they are buried in a nonpolar environment (hydrocarbon chains), that’s why they’re nonpolar & hydrophobic
What do you call the mixture of triglycerides containing high proportion of saturated fatty acids?
fats
properties of fatty acids are carried over to triglycerides
What do you call the mixture of triglycerides containing high proportion of unsaturated fatty acids and short-chain saturated fatty acids?
oils
properties of fatty acids are carried over to triglycerides
What are the two classifications of complex lipids?
- phospholipids
- glycolipids
What type of complex lipid contains an alcohol, two fatty acids, and a phosphate group?
Phospholipids
What type of complex lipid contains carbohydrates?
Glycolipids
What are the two types of phospholipids?
- glycerophospholipids
- sphingolipids
in glycerophospholipids, the backbone is glycerol; in sphingolipids, backbone is sphingosine
The lipid bilayer contains ____ fatty acids that accounts for the membrane’s fluidity
unsaturated fatty acids
What do you call the reaction of a triacylglycerol with a base producing glycerol and three molecules of fatty acids?
saponification
What do you call the type of phospholipid with a glycerol backbone, 2 fatty acids, and a phosphate group esterified to another alcohol?
glycerophospholipid
or phosphoacylglycerol
In the event that the alcohol to the phosphate group of the glycerophospholipid is esterified to a choline, what do you now call the compound?
phosphatidylcholine
or lecithin
In the event that the alcohol to the phosphate group of the glycerophospholipid is esterified to a ethanolamine or serine, what do you now call the compound?
phosphatidylethanolamine
or cephalin
abundant in egg yolk, wheat germ, yeast
In the event that the alcohol to the phosphate group of the glycerophospholipid is phosphate-esterified to inositol, what do you now call the compound?
phosphatidylinositol
what do you call the most abundant lipid in most cell membranes that has a polar head and two nonpolar tails?
phospholipids
phosphoacylglycerol
What do you call the type of phospholipids that have a sphingosine backbone?
sphingolipids
What do you call the bond between a fatty acid and a sphingosine?
ceramide
What types of lipids are the most important lipids in myelin sheaths of nerve cells and associated in diseases such as multiple sclerosis?
sphingomyelins
What do you call the lipids that contain 3 cyclohexane rings and 1 cyclopentane rings fused together?
steroids
What is the most abundant and most important steroid in the human body?
cholesterol
What do you call the spherically-shaped molecules that transports cholesterol and fat?
Lipoproteins
What are the 4 types of lipoproteins?
- HDL
- LDL
- VLDL
- Chylomicrons
What steroid is considered as the precursor for the synthesis of other steroids and is derived from squalene?
Cholesterol
Most cholesterol is transported in the body by what type of lipoproteins?
LDL
What do you call the group of signal lipids that are derived from the metabolism of arachidonic acid by cyclooxygenase?
eicosanoids
Identify the type of eicosanoids
- stimulates muscle contraction
- anticoagulant
- controls blood pressure
- stimulates muscle contraction
- from prostanoic acid
Prostaglandins
Identify the type of eicosanoids
- induces platelet aggregation
- induces vasoconstriction
Thromboxanes
Identify the type of eicosanoids
- produces muscle contractions, especially in the lungs
- occurs mainly in leukocytes
- drugs inhibit the synthesis of this eicosanoid (in asthma)
Leukotrienes
Identify the fat-soluble vitamin
- Isoprenoid alcohol that play a key role in visio
- can be biosynthesized from B-carotene
Vitamin A
Retinoic Acid
Identify the fat-soluble vitamin
- Essential for bone health
- Deficiency leads to bone defects
Vitamin D
Cholecalciferol
Identify the fat-soluble vitamin
- powerful antioxidant
- important for skin health
Vitamin E
Alpha-Tocopherol
Identify the fat-soluble vitamin
- Important in the synthesis of prothrombin and protein factors in platelets
- Deficiency leads to diminished intestinal absorption of lipids
Vitamin K
phylloquinone’ menaquinone
What are the three reagents involved in the isolation of lipids from eggs?
- Ethanol
- Hexane
- Acetone
What reagent from the isolation process denatures the proteins and disrupts the lipoprotein complexes of egg yolk?
Ethanol
What reagent from the isolation process was used to remove neutral or least polar lipids?
Hexane
What reagent from the isolation process was used to provides a mild dehydration condition wherein:
- H2O content decreases; thus, lipids are extracted
- polar lipid w/ neutral lipids will further precipitate
Acetone
Column chromatography is based on what principle wherein a solid holds molecules of a gas or liquid or solute as a thin film?
Adsorption
What are the reagents used in column chromatography?
- Petroleum ether:ethyl ether (9:1)
- 5% MetOH in DCM
- DCM:MetOH:H2O (1:3:1)
arranged from least polar to most polar*
Stationary phase in TLC of lipids?
SIlica gel
Identify the visualizing agent in TLC of lipids
- appears as yellow-brown spots
- oxidation of unsaturated fatty acids is involved as a rxn
I2
iodine
Identify the visualizing agent in TLC of lipids
- appears as blue-violet spots
- detected in here are the free amino acid grps
Ninhydrin
What are the standards used in TLC of lipids?
- Cholesterol
- Lecithin
Identify the test based on reagents
- ethanol:butanol (3:1)
- NH2OH-HCl
- NaOH
- FeCl3
- HCl
Hydroxamic test
Identify the test based on reagents
- KHSO4
- Water bath
Acrolein test
Identify the test based on reagents
- conc. H2SO4
- acetic anhydride
Liebermann-Burchard test
Identify the test based on reagents
- Bismuth nitrate
- 3M HNO3
- KI
Kraut’s test
Identify the test based on reagents
- 6M HNO3
- 6M NaOH
- Molybdate rgt
- Ascorbic acid
Ascorbic Acid method
Test for Phosphate
Identify the test based on reagents
- triketohydrindene hydrate (ninhydrin in EtOH)
Ninhydrin test
Identify the test based on reagents
- 5% Bromine/Iodine solution
Test for lipid unsaturation
Identify the test based on reagents
- 1% ethanolic a-naphthol
- conc. H2SO4
Molisch test
Identify the test based on principle and purpose
- complexation rxn
- detects presence of carboxylic acid esters
- detects TAGs, glycerophospholipids, cholesteryl esters
Hydroxamic test
test for ester
Identify the test based on principle and purpose
- dehydration and oxidation
- detects glycerol
- detects TAGs, glycerophospholipids
Acrolein test
test for glycerol
Identify the test based on principle and purpose
- esterification with acetic anhydride & epimerization of double bond at C5
- detects presence of unsaturated sterols
- detects cholesterol
Libermann-Burchard test
test for cholesterol
Identify the test based on principle and purpose
- complexation rxn
- detects presence of choline
Kraut’s test
Identify the test based on principle and purpose
- reagents react in acidic medium with orthophosphate to form an acid that’ll be reduced later by ascorbic acid
- detects phosphate
Test for Phosphate
Ascorbic acid method
Identify the test based on principle and purpose
- oxidative deamination followed by condensation
- detects presence of a-amino grp
Ninhydrin test
Identify the test based on principle and purpose
- addition reaction
- detects presence of double bonds (degree of unsaturation)
Test for Lipid Unsaturation
Identify the positive result of the test
Hydroxamic test
Test for ester
burgundy color
Identify the positive result of the test
Acrolein test
Test for glycerol
burnt fat odor
Identify the positive result of the test
Libermann-Burchard test
Test for cholesterol
emerald green solution
Identify the test based on principle and purpose
Kraut’s test
dark orange to red ppt
Identify the test based on principle and purpose
Test for phosphate
Ascorbic acid method
molybdenum blue solution
or cerulean
Identify the test based on principle and purpose
Test for Lipid Unsaturation
reddish brown color or violet coloration
What is the identity of the first eluate in the column chromatography?
- Triglycerides
- Cholesteryl ester
i2 mga most nonpolar
What is the identity of the second eluate in the column chromatography?
cholesterol
What is the identity of the third eluate in column chromatography?
- Glycerophospholipids
- Sphingomyelin
most polar
Which tests will be positive for triacylglycerides?
- Hydroxamic test
- Acrolein
- Test for unsaturation (depende sa fatty acid chain)
Which tests will be positive for cholesteryl esters?
- Hydroxamic test
- Liebermann-Burchard test
Which tests will be positive for glycerophospholipids?
- Hydroxamic
- Acrolein
- Kraut’s (phosphatidylcholine)
- Test for unsaturation (depende ulet sa fatty acid chain)
- Ninhydrin (for Phosphatidylenolamine)
Which tests will be positive for sphingomyelin?
- Kraut’s
- Test for unsaturation (depende sa fatty acid chain)
