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Biochemistry > LIPIDS > Flashcards

LIPIDS Flashcards

1
Q

Lipids(3)

A

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

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2
Q

Classification of lipids

A

Simple
Compound
Derived
Lipids complexed to other compounds

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3
Q

Simple lipids 1 + 2egs

A

Esters of fatty acids with glycerol or other higher alcohols
Triacylglycerol / triglycerides/ neutral fat
Waxes

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4
Q

Compound lipids 1
A 1234
B 12

A

Fatty acids esterified w alcohol but in addition contains other groups

A. Phospholipids, containing phosphoric acid.

  1. Nitrogen containing glycerophosphatides:
    i. Lecithin (phosphatidyl choline)
    ii. Cephalin (phosphatidyl ethanolamine)
    iii. Phosphatidyl serine
  2. Non-nitrogen glycerophosphatides
    i. Phosphatidyl inositol
    ii. Phosphatidyl glycerol
    iii. Diphosphatidyl glycerol (cardiolipin)
  3. Plasmalogens, having long chain alcohol
    i. Choline plasmalogen
    ii. Ethanolamine plasmalogen
  4. Phospho sphingosides, with sphingosine
    Sphingomyelin

B) Non-phosphorylated lipids

  1. Glycosphingolipids (carbohydrate)

i. Cerebrosides (ceramide monohexosides)
ii. Globosides (ceramide oligosaccharides)
iii. Gangliosides (ceramide + oligosaccharides + N-acetyl neuraminic acid)

  1. Sulpholipids or sulfatides
    i. Sulphated cerebrosides
    ii. Sulphated globosides
    iii. Sulphated gangliosides
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5
Q

Derived lipids 1 + eg 6

A

Compounds which are derived from lipids or precursors of lipids which possess the characteristics of lipid

Eg fatty acids
steroids
prostaglandins
leukotreines
terpenes
dolichols

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6
Q

Lipids complexed to other compounds

A

Proteolipids
Lipoproteins

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7
Q

Poly unsaturated fatty acids
Definition
Similar to saturated
All naturally occurring fa (3)

A

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

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8
Q

Pufa examples
No of double bond and omega

A

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

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9
Q

Clinical significance of PUFA (9)

A

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,

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10
Q

Features of Pufa (8)

A

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

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11
Q

Eicosanoids (3)

A

They are polyenoic fa
They are prostanoids and leukotreines
Prostanoids - prostaglandins
Prostacyclins
Thromboxanes

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12
Q

Zellweger syndrome (3)

A

Proteins are not transported into peroxisomes
This leads to formation of empty peroxisomes or peroxisomal ghosts inside the cells
Protein targeting defects

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13
Q

Saponification

A

When triglycerides are hydrolysed by alkali the process is known as saponification
Products are glycerol and soap

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14
Q

Saponification Number
Depends on

A

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

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15
Q

Saponification Number of
Human fat
Butter
Coconut oil

A

194-198
210-230
253-262

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16
Q

Iodine Number
Index
Examples

A

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

17
Q

Rancidity of fat(2)

A

Fats and oils tend to become rancid

Term rancidity refers to the
appearance of an unpleasant smell and taste for fats and oils

18
Q

Hydrolytic rancidity

A

Due to partial hydrolysis of triacylglycerol molecules due to traces of hydrolytic enzymes present in naturally occurring fats and oils.

19
Q

Oxidative rancidity (2)

A

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

20
Q

Prevention of Oxidative rancidity (3)

A

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

21
Q

Cyclic hydrocarbons(3)

A

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

22
Q

Liposomes(2)

A

Spherical vesicles consisting of one or more phospholipid bilayers.

A lipid bilayer will close onto itself under appropriate conditions to form liposomes

23
Q

Formation of liposomes(2)

A

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

24
Q

Uses of liposome (4)

A

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

25
Q

Second generation liposomes

A

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

26
Q

Trans fatty acids. Present in(7)

A

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

27
Q

Trans fatty acids adversely affect (6)

A

Multiple risk factors Inc

Plasma lipids and lipoproteins
Systemic inflammation
Endothelial dysfunction
Insulin resistance
Diabetes
Adiposity

28
Q

Properties of fa (5)

A

Hydrogenation
Halogenation
MP
Salt formation
Ester formation

29
Q

Hydrogenation (2)
Eg

A

Unsaturated fa - saturated fa
Hydrogenation of oils can lead to solidification and saturation eg vanaspati

30
Q

Halogenation (4)
Eg

A

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

31
Q

MP (5)
Examples

A

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

32
Q

salt formation (5)

A

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

33
Q

Ester formation (3)

A

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

Biochemistry (5 decks)

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