its a presentation on lipid

2. LIPIDS
Lipids(Greek: lipos, fat) are substances of biological
origin that are soluble in organic solvents such as
chloroform and methanol but are only sparingly
soluble in water.

3. 1. Fatty acids
•Fatty acids are carboxylic acids with long-chain(C4to C36)
hydrocarbon side groups.
• They are rarely free in nature but, rather, occur in
esterified form as the major components of the various
lipids.
•In some fatty acids, this chain is unbranched and fully
saturated (contains no double bonds); in others the chain
contains one or more double bonds i.e unsaturated.

4. In nearly all naturally occurring unsaturated fatty acids,
the double bonds are in the cis configuration.
Trans fatty acids are produced by fermentation in the
rumen of dairy animals and are obtained from dairy
products and meat.They are also produced during
hydrogenation of fish or vegetable oils.

6. Diets high in trans fatty acids correlate with increased
blood levels of LDL (bad cholesterol) and decreased
HDL (good cholesterol),
It is generally recommended that one avoid large
amounts of these fatty acids.
Unfortunately, junk foods tend to be high in trans fatty
acids.

7. Fatty acids may be further subdivided as follows:
(1) Monounsaturated :containing one double bond.
(2) Polyunsaturated: containing two or more double bonds.
(3) Eicosanoids: These compounds, derived from
eicosa- (20-carbon) polyenoic fatty acids, comprise the
prostanoids, leukotrienes (LTs),and
lipoxins (LXs).
Prostanoids include prostaglandins (PGs), prostacyclins
(PGIs), and thromboxanes (TXs).

8. Nomenclature
• C-1 being the carboxyl carbon.
• specify the chain length and number of double bonds,
separated by a colon.
for example, the 16-carbon saturated palmitic acid is
abbreviated 16:0,
the 18-carbon oleic acid, with one double bond, is
18:1.
• The positions of any double bonds are specified by
superscript numbers following ∆(delta); a 20-carbon
fatty acid with one double bond between C-9 and C-10
and another betweenC-12 and C-13 is designated
20:2(∆9,12).

9. The physical properties of the fatty acids, and of
compounds that contain them……….
• are largely determined by the length and degree of
unsaturation of the hydrocarbon chain.
• The nonpolar hydrocarbon chain accounts for the poor
solubility of fatty acids in water.
• The longer the fatty acyl chain and the fewer the double
bonds, the lower is the solubility in water.
• The carboxylic acid group is polar (and ionized at neutral
pH) and accounts for the slight solubility of short-chain
fatty acids in water.

10. Melting points are also strongly influenced by the
length and degree of unsaturation of the hydrocarbon
chain.
At room temperature the saturated fatty acids from 12:0
to 24:0 have a waxy consistency, whereas unsaturated
fatty acids of these lengths are oily liquids.
This difference in melting points is due to different degrees
of packing of the fatty acid molecules.

11. fully saturated compounds, free rotation around each
carbon–carbon bond gives the hydrocarbon chain
great flexibility; the most stable conformation is the fully
extended form, in which the steric hindrance of neighboring
atoms is minimized.
These molecules can pack together tightly in nearly
crystalline arrays, with atoms all along their lengths in van
der Waals contact with the atoms of neighboring molecules.
I

12. In unsaturated fatty acids, a cis double bond forces a kink in
the hydrocarbon chain. Fatty acids with one or several such
kinks cannot pack together as tightly as fully saturated fatty
acids, and their interactions with each other are therefore
weaker. Because it takes less thermal energy to disorder
these poorly ordered arrays of unsaturated fatty acids, they
have markedly lower melting points than saturated fatty
acids of the same chain length

13. Functional aspects:
• Prostaglandins exist in virtually every mammalian tissue,
acting as local hormones; they have important physiologic
and pharmacologic activities.
• Maintains fluidity of membrane.
• Important to fight high cholesterols and heart disease.
• Have role in cell signalling.

14. 2. Storage Lipid

15. • The simplest lipids constructed from fatty acids are the
triacylglycerols,also referred to as triglycerides, fats, or
neutral fats.
• Triacylglycerols are composed of three fatty acids each in
ester linkage with a single glycerol.
• May contain same kind or two/more different kind of fatty
acids.
• Triacylglycerols are nonpolar, hydrophobic molecules,
essentially insoluble in water and have lower specific
gravities than water,
Triacylglycerols

17. 1-Palmitoleoyl-2-linoleoyl-3-stearoylglycerol

18. • Fats and oils differ only in that fats are solid and
oils are liquid at room temperature.
• They are complex mixtures of simple and mixed
triacylglycerols whose fatty acid compositions vary
with the organism that produced them.
• Plant oils are usually richer in unsaturated fatty acid
residues than are animal fats, as the lower melting
points of oils imply.

19. Functional aspects:
•Triacylglycerols form a separate phase of microscopic, oily
droplets in the aqueous cytosol, serving as depots of
metabolic fuel.
• In vertebrates, specialized cells called adipocytes, or fat
cells,store large amounts of triacylglycerols as fat droplets
that nearly fill the cell .
• Triacylglycerols are also stored as oils in the seeds of many
types of plants,providing energy and biosynthetic precursors
during seed germination

20. •In some animals, triacylglycerols stored under the
skin serve not only as energy stores but as insulation
against low temperatures. Seals, walruses, penguins, and
other warm-blooded polar animals are amply padded
with triacylglycerols.
•In hibernating animals (bears) the huge fat reserves
accumulated before hibernation serve the dual purposes of
insulation and energy storage .

21. Waxes
•Biological waxes are esters of long-chain (C14 to C36)
saturated and unsaturated fatty acids with long-chain
(C16to C30) alcohols.
• Their melting points (60 to 100◦C) are generally higher
than those of triacylglycerols.

22. Functional aspects
• In plankton,waxes are the chief storage form of metabolic
fuel.
• Certain skin glands of vertebrates secrete waxes to protect
hair and skin and keep it pliable, lubricated, and waterproof.
• Birds, particularly waterfowl,secrete waxes from their preen
glands to keep their feathers water-repellent.
• The shiny leaves of rhododendrons, poison ivy, and many
tropical plants are coated with a thick layer of waxes, which
prevents excessive evaporation of water and protects against
parasites.

23. 2. Structural Lipids in Membranes

24. A.

25. Glycerophospholipids
• also called phosphoglycerides
• membrane lipids in which two fatty acids are attached
in ester linkage to the first and second carbons of glycerol,
and a highly polar or charged group is attached through a
phosphodiester linkage to the third carbon.

26. • Glycerophospholipid sare named as derivatives of the parent
compound, phosphatidic acid, according to the polar alcohol in the
head group.

27. Sphingolipids
• major membrane components,
• are derivatives of the C18 amino alcohols sphingosine,
dihydrosphingosine etc.

29. Functional aspects:
• Phospholipids are the main lipid constituents of
membranes
• Phosphatidylcholines (Lecithins) are the most abundant
phospholipids of the cell membrane.
• Choline is important in nervous transmission, as
acetylcholine, and as a store of labile methyl groups.
• Phosphatidylinositol Is a Precursor of Second
Messengers
• Cardiolipin Is a Major Lipid of Mitochondrial Membranes
• Plasmalogens Occur in Brain & Muscle

30. • Sphingomyelins are present in the plasma membranes of
animal cells and are especially prominent in myelin, a
membranous sheath that surrounds and insulates the
axons of some neurons—thus the name “sphingomyelins.”

31. B.

32. Glycosphingolipids
• occur largely in the outer face of plasma membranes
• have head groups with one or more sugars connected
directly to the -OH at C-1 of the ceramide moiety
• they do not contain phosphate
Ceramide

33. Example:
Cerebrosides have a single sugar linked to ceramide; those
with galactose are characteristically found in the plasma
membranes of cells in neural tissue, and those with glucose
in the plasma membranes of cells in non neural tissues.
Globosides are neutral (uncharged) glycosphingolipids with
two or more sugars, usually D-glucose, D-galactose, or N-
acetyl-D-galactosamine.
• The galactose residues of some galactocerebrosides,
however,are sulfated at their C3 positions to form ionic
compounds known as sulfatides

34. Gangliosides
• the most complex sphingolipids
• have oligosaccharides as their polar head groups and one
or more residues of N-acetylneuraminic acid at the termini.
• Sialic acid gives gangliosides the negative charge at pH 7.

35. Functional aspects
• Glycolipids/Glycosphingolipids are widely distributed in
every tissue of the body, particularly in nervous tissue
such as brain. They occur particularly in the outer leaflet
of the plasma membrane, where they contribute to cell
surface carbohydrates.
• Glycosphingolipids are determinants of blood groups.The
human blood groups (O, A, B) are determined in part by
the oligosaccharide head groups of these
glycosphingolipids

36. • Gangliosides are concentrated in the outer surface of
cells, where they present points of recognition for
extracellular molecules or surfaces of neighboring cells.
• The kinds and amounts of gangliosides in the plasma
membrane change dramatically during embryonic
development. Tumor formation induces the synthesis of a
new complement of gangliosides.

37. C.

40. Sterols
• structural lipids present in the membranes of most
eukaryotic cells.
• The characteristic structure is the steroid nucleus,
consisting of four fused rings, three with six carbons and
one with five.
Steroid nucleus

41. • Cholesterol, the major sterol in animals,is precursor to a
wide variety of steroids. It is widely distributed in all cells
of the body but particularly in nervous tissue. It is a major
constituent of the plasma membrane and of plasma
lipoproteins
• Stigmasterol in plants and Ergosterol in fungi. Bacteria
cannot synthesize sterols; a few bacterial species,
however, can incorporate exogenous sterols into their
membranes.
Cholesterol

42. • The sterols serve as precursors for a variety of products
with specific biological activities.
Steroid hormones, for example, are potent biological signals
that regulate gene expression.
Bile acids are polar derivatives of cholesterol that act as
detergents in the intestine, emulsifying dietary fats to make
them more readily accessible to digestive lipases.
• Ergosterol Is a Precursor of Vitamin D

43. Amphipathic lipids self-orient at oil:water interfaces:
In general, lipids are insoluble in water since they contain a
predominance of nonpolar (hydrocarbon) groups.
Therefore, part of the molecule is hydrophobic,or water-
insoluble; and part is hydrophilic,or water-soluble.
Such molecules are described as amphipathic.

45. How hydrophilic and hydrophobic molecules interact
differently with water

46. For the above reason, lipid molecules spontaneously
aggregate to bury their hydrophobic tails in the interior
and expose their hydrophilic heads to water. Depending
on their shape, they can do this in either of two ways:
1.They can form spherical micelles, with the tails inward,
or
2. They can form bimolecular sheets, or bilayers, with the
hydrophobic tails sandwiched between the hydrophilic
head groups

48. When a critical concentration of these lipids is present
in an aqueous medium, they form micelle.
Liposomes may be formed by sonicating an amphipathic lipid
in an aqueous medium. They consist of spheres of lipid
bilayers that enclose part of the aqueous medium. They are
of potential clinical use—particularly when combined with
tissue specific antibodies—as carriers of drugs in the
circulation, targeted to specific organs, e.g, in cancer therapy.
Aggregations of bile salts into micelles and liposomes and the
formation of mixed micelles with the products of fat
digestion are important in facilitating absorption of lipids
from the intestine.

50. Lipids & vitamins:
Vitamins D, A, E, and K are fat-soluble compounds made up
of isoprene units. All play essential roles in the metabolism or
physiology of animals.
• Vitamin D is precursor to a
hormone that regulates calcium
Metabolism
• Vitamin A furnishes the visual pigment of the vertebrate
eye and is a regulator of gene expression during epithelial cell
growth.
• Vitamin E functions in the protection of membrane lipids
from oxidative damage,
• Vitamin K is essential in the blood-clotting process.

51. Other impotant functions of lipids:
• Ubiquinones(also called coenzyme Q) and plastoquinones,
also isoprenoid derivatives, function as electron carriers in
mitochondria and chloroplasts,respectively.
• Dolichols (isoprenoid alcohols ) activate and anchor sugars
on cellular membranes for use in the synthesis of certain
complex carbohydrates, glycolipids, and glycoproteins.
• 1 gm mol of fat generates about 9 Kcal energy.