LIPIDS Flashcards
Lipids(3)
long chain fatty acids of alcohol
heterogeneous group of compounds of biochemical importance
defined as compounds which are relatively insoluble in water but freely soluble in nonpolar organic solvents like benzene chcl3 ether hot alcohol acetone etc
Classification of lipids
Simple
Compound
Derived
Lipids complexed to other compounds
Simple lipids 1 + 2egs
Esters of fatty acids with glycerol or other higher alcohols
Triacylglycerol / triglycerides/ neutral fat
Waxes
Compound lipids 1
A 1234
B 12
Fatty acids esterified w alcohol but in addition contains other groups
A. Phospholipids, containing phosphoric acid.
- Nitrogen containing glycerophosphatides:
i. Lecithin (phosphatidyl choline)
ii. Cephalin (phosphatidyl ethanolamine)
iii. Phosphatidyl serine - Non-nitrogen glycerophosphatides
i. Phosphatidyl inositol
ii. Phosphatidyl glycerol
iii. Diphosphatidyl glycerol (cardiolipin) - Plasmalogens, having long chain alcohol
i. Choline plasmalogen
ii. Ethanolamine plasmalogen - Phospho sphingosides, with sphingosine
Sphingomyelin
B) Non-phosphorylated lipids
- Glycosphingolipids (carbohydrate)
i. Cerebrosides (ceramide monohexosides)
ii. Globosides (ceramide oligosaccharides)
iii. Gangliosides (ceramide + oligosaccharides + N-acetyl neuraminic acid)
- Sulpholipids or sulfatides
i. Sulphated cerebrosides
ii. Sulphated globosides
iii. Sulphated gangliosides
Derived lipids 1 + eg 6
Compounds which are derived from lipids or precursors of lipids which possess the characteristics of lipid
Eg fatty acids
steroids
prostaglandins
leukotreines
terpenes
dolichols
Lipids complexed to other compounds
Proteolipids
Lipoproteins
Poly unsaturated fatty acids
Definition
Similar to saturated
All naturally occurring fa (3)
Fatty acids having more than one double bond in their structure
In the reaction of carboxylic group but also shows properties due to presence of double bond
Cis configuration.
However in body during metabolism trans fa are formed
Pufa exist in cis configuration in naturally occurring lipids
Pufa examples
No of double bond and omega
Linoleic C18 2 w6 family 9 12
Linolenic C18 3 w3 9 12 15
Arachidonic C20 4 w6 5 8 11 14
Oleic C20 1 w9
Clinical significance of PUFA (9)
Used for esterification and excretion of cholesterol hence they are Antiatherogenic
Omega 3 fatty acids play significant role in
Infant development
Cancer
Cardiovascular diseases
Various mental illness including depression attention deficit hyperactivity disorder and dementia
Have pleiotropic effects including effects against
Inflammation
Platelet aggregation
Hypertension
Hyperlipidemia
These beneficial effects maybe mediated through several distinct mechanisms including alterations in cell membrane composition and function gene expression or eicosanoid production
Persons with normal diet will not have any deficiency but those on parenteral nutrition for long will have
Elevated Pufa is seen in zellweger syndrome
DHA which is important for brain function can be either obtained from diet or synthesized in the body from alpha linolenic acid
DHA levels are low in patients with retinitis pigmentosa
DHA is present in high conc in fish oils,
Features of Pufa (8)
They are essential fa
Arachidonic acid is the precursor of prostaglandins.
Ara can be synthesized in the body from linoleic acid if it is supplied through diet
Pentanoic acid present in fish oils is if great nutritional importance (w3 unsaturated fa)
Eicosanoids can be synthesized from ara
Form integral part of mito membrane. In deficiency of Pufa efficiency biological oxidation is reduced
As there are double bonds in the cis configuration (naturally occurring) pufa, these molecules cannot be closely packed. Hence they increase the fluidity of membrane
As pufas are easily liable to undergo peroxidation membranes containing pufas are more prone to damage by freeradicals
Eicosanoids (3)
They are polyenoic fa
They are prostanoids and leukotreines
Prostanoids - prostaglandins
Prostacyclins
Thromboxanes
Zellweger syndrome (3)
Proteins are not transported into peroxisomes
This leads to formation of empty peroxisomes or peroxisomal ghosts inside the cells
Protein targeting defects
Saponification
When triglycerides are hydrolysed by alkali the process is known as saponification
Products are glycerol and soap
Saponification Number
Depends on
No. Of milligrams of potassium hydroxide required to saponify 1g of fat.
It is an indication of molecular weight of fat and is inversely proportional to it
Saponification Number of
Human fat
Butter
Coconut oil
194-198
210-230
253-262
Iodine Number
Index
Examples
No. Of grams of iodine taken up by 100 gram of fat
Index of degree of unsaturation and is directly proportional to the content of unsaturated fa
Higher Ino. Higher degree of unsaturation
Butter - 28
Sunflower oil - 130
Rancidity of fat(2)
Fats and oils tend to become rancid
Term rancidity refers to the
appearance of an unpleasant smell and taste for fats and oils
Hydrolytic rancidity
Due to partial hydrolysis of triacylglycerol molecules due to traces of hydrolytic enzymes present in naturally occurring fats and oils.
Oxidative rancidity (2)
Result of partial oxidation of unsaturated fa with resultant formation of epoxides and peroxides of small molecular weight fatty acids by peroxidases and free radicals
This process will affect the integrity of biomembranes leading to cell death
Prevention of Oxidative rancidity (3)
Many natural fats and oils may contain antioxidants (eg Vitamin E) which prevent the occurrence
Pufa are more easily oxidised
So vegetable oils with high content of Pufa are usually preserved with addition of antioxidants
Cyclic hydrocarbons(3)
Repeated heating of oils would lead to the formation and polymerization of cyclic hydrocarbons
This will impart an unpleasant taste and colour to the oil
Coconut oil having medium chain saturated fa will withstand such polymerization
Liposomes(2)
Spherical vesicles consisting of one or more phospholipid bilayers.
A lipid bilayer will close onto itself under appropriate conditions to form liposomes
Formation of liposomes(2)
Prepared by sonication of mixtures of phospholipids and cholesterol
When mixed in water under special conditions phospholipids arrange themselves to form a bilayer membrane which encloses some of the water in a phospholipid sphere
Uses of liposome (4)
Acts as carriers
To deliver drugs proteins enzymes genes etc
To target organs
Important applications in
cancer chemotherapy
Antimicrobial therapy
Gene therapy
Vaccines
Diagnostic imaging
Oral iron preparations trapped in liposomes have been introduced to avoid gastric irritation (sucrosomial iron)
Liposomes entrapped drugs exhibit superior pharmacological properties than those formed with conventional formulations
Second generation liposomes
Long circulating liposomes are obtained my modulating the lipid composition, size and charge of the vesicle.
Liposomes with modified surfaces have also been developed using several molecules such as glycolipids or sialic acids
Trans fatty acids. Present in(7)
Dairy products
Hydrogenated edible oils
Generally considered to be injurious to health
However used in food industry to increase shelf life of fried food
Oils containing pufa also have high content of trans fa
Fast food prep high content
High in processed food where partially hydrogenated vegetable oils are used for cooking
Trans fatty acids adversely affect (6)
Multiple risk factors Inc
Plasma lipids and lipoproteins
Systemic inflammation
Endothelial dysfunction
Insulin resistance
Diabetes
Adiposity
Properties of fa (5)
Hydrogenation
Halogenation
MP
Salt formation
Ester formation
Hydrogenation (2)
Eg
Unsaturated fa - saturated fa
Hydrogenation of oils can lead to solidification and saturation eg vanaspati
Halogenation (4)
Eg
Treated with halogens under mild
Unsat fa take 2 halogen atoms at each double bond
To form halogen derivative of fa
No of X taken up will depend on no. Of double bonds and is an index of the degree of unsaturation
*Iodine
MP (5)
Examples
Short and medium fa - liquids
Long chain fa - solids
Solubility in water decreases
MP and Bp in chain length
Unsat lowe MP
Stearic acid 69
Oleic acid 13
Linoleic acid -5
Linolenic -10
salt formation (5)
Sat and un forms salt with alkali
Na and K salts of long chain fa are called soaps.
Calcium and Mg soaps are insoluble
Calcium soaps are used in grease
Alkyl sulfate and alkyl sulfonate are not pptd by hard water and are used as detergents
Ester formation (3)
Sat and unsat form esters with alcohols especially with glycerols
Fa can form mono di or tri esters with OH groups of glycerol
Triglycerides or triacylglycerols are known as neutral fat
