lipids. *the lipids are a heterogeneous group of compounds, including fats, oils, steroids, waxes,...
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lipids
*The lipids are a heterogeneous group of compounds,including fats, oils, steroids, waxes, and related compounds, which are related more by their physical than by their chemical properties. *They have the common property of being (1) relatively insoluble in water .(2) soluble in nonpolar solvents such as ether andchloroform. *Lipid is not polymers.
• Storage form of energy .• Thermal Insulation .• Protection for delicate organs .• Key component of cell membranes .• Precursors of steroid hormones as sex hormones .
Lipid Functions
1. Simple lipids: Esters of fatty acids with various alcohols.a. Fats: Esters of fatty acids with glycerol. Oils are fats in the liquid state.b. Waxes: Esters of fatty acids with higher molecular weight monohydric alcohols.2. Complex lipids: Esters of fatty acids containing other groups in addition to an alcohol and a fatty acid.a. Phospholipids: Lipids containing, in addition to fatty acids and an alcohol, a phosphoric acid residue. They frequently have nitrogen containing bases and other substituent, eg, in glycerophospholipids the alcohol is glycerol and in sphingophospholipids the alcohol is sphingosine.
Classification of lipids
b. Glycolipids (glycosphingolipids): Lipids containing a fatty acid, sphingosine, and carbohydrate.
c. Other complex lipids: Lipids such as sulfolipidsand aminolipids. Lipoproteins.
3 .Precursor and derived lipids: These include fatty acids, glycerol, steroids, other alcohols, lipid-soluble vitamins, and hormones.
* Acylglycerols (glycerides),cholesterol, and
cholesteryl esters (because they are uncharged ) are termed neutral lipids.
*Even chain fatty acids are common, odd chain fatty acids are rare, but 3 ‘C’ & 5 ‘c’ are common .
*Fatty acids with 14 – 20 Carbon are commonly seen in natural lipids.
* Saturated Fatty acids do not contain double bond ex. Palmitic acid. Unsaturated Fatty acids contain one or more double bonds.The double bond is always in cis configuration . One double bond – Mono Unsaturated ex. Oleic acid Two or more double bonds – Poly unsaturated fatty acids ex. Linoleic acid Linolenic acid Arachidonic acid
ESSENTIAL FATTY ACIDS : *The fatty acids which are not synthesized in the body and they should be supplied in the diet are known as Essential Fatty Acids. *All are PolyUnsaturated Fatty Acids eg.
Linoleic acid , Linolenic acid Arachidonic acid .
Fatty acid composition of three food fats. Olive oil, butter, and beef fat consist of mixtures of triacylglycerols, differing in their fatty acid composition. The melting points of these fats—and hence their physical state at room temperature (25 C)—are a direct function of their fatty acid composition. Olive oil has a high proportion of long-chain (C16 and C18) unsaturated fatty acids, which account for its liquid state at 25 C. The higher proportion of long-chain (C16 and C18) saturated fatty acids in butter increases its melting point, so butter is a soft solid at room temperature. Beef fat, with an even higher proportion of long-chain saturated fatty acids, is a hard solid
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Triacylglyerol
Fats : triglycerides which are solid at room temperature ( most saturated triglycerides, e.g. beef, fat, or lard)
Oils : triglycerides which are liquid at room temperature ( most triglycerides with several unsaturation, e.g. corn oil, peanut oil, or fish oils)
- Triacylglycerols are esters of glycerol with fatty acids . - Fats and oils that are widely distributed in both plants & animals are chemically triacylglycerols. a) SIMPLE TRIACYLGLYEROLS - All the three fatty acids are same type . b) MIXED TRIACYLGLYCEROLS Contains 2-3 different types of fatty acids , more common .
Triacylglycerols
Triglycerides
O
OH
OH
R
O
O
OH
O
R
O
R
O
O
O
R
O
R
O
OR
O
MONOGLYCERIDE DIGLYCERIDE TRIGLYCERIDE
Function: storage of energy
Structure of triglycerides
*Biological waxes are esters of long-chain (C14 to C36) saturated or unsaturated fatty acids with long-chain (C16 to C30) alcohols. * Their melting points (60 to 100 C) are generally higher than those of triacylglycerols.
* Waxes serve a diversity of other functions related to their water-repellent properties and their firm consistency.
WAXES
H3C (CH2)14 C
O
O CH2 (CH2)28-CH3
long chain alcohol
fatty acid
A honeycomb, constructed of beeswax, is firm at25C and completely impervious to water
Triacontanoylpalmitate, the major component of beeswax, is an ester of palmitic acid with the alcohol triacontanol .
* 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 many tropical plants are coated with a thick layer of waxes, which prevent excessive evaporation of water and protects against parasites.
* Biological waxes find a variety of applications in the pharmaceutical, cosmetic, and other industries. They are widely used in the manufacture of lotions, ointments, and polishes.
* In plankton, the free-floating microorganisms at the bottom of the food chain for marine animals waxes are the chief storage form of metabolic fuel.
- Phospholipids are compound lipids containing Glycerol ,Fatty acid ,Phosphate and other groups .Two Classes : 1-Glycerophospholipids In this group alcohol is glycerol . 2- Spingophospholipids In this group alcohol is sphingosine . Glycerophospholipids : - Glycerophospholipids Major lipids in Biological membrane . - Glycerol – 3-phosphate is esterified with 2 Fatty acids usually c1 is esterified with Saturated Fatty acid, and C2 is esterified with unsaturated fatty acid. 1. Phosphatidic acid : 1. Phosphatidic acid is simplest phospholipid .
Phospholipids
THE PRINCIPLE CLASSES OF STORAGE AND MEMBRANE LIPIDS
All these lipids have either glycerol or sphingosin as the backbone .
■The sphingolipids contain sphingosine, a long chain aliphatic amino alcohol, but no glycerol.
- Sphingomyelin has, in addition to phosphoricacid and choline, two long hydrocarbon chains,
one contributed by a fatty acid and the otherby sphingosine .
■The polar lipids, with polar heads and nonpolartails, are major components of membranes. - The most abundant are the glycerophospholipidswhich contain fatty acids esterified to two ofthe hydroxyl groups of glycerol, and a secondalcohol, the head group, esterified to the thirdhydroxyl of glycerol via a phosphodiester bond.
- Other polar lipids are the sterols. ■Glycerophospholipids differ in the structure of
their head group; common glycerophospholipidsare phosphatidylethanolamine and phosphatidylcholine. The polar heads of the glycerophospholipids carry electric charges at pH near 7.
* Glycolipids are composed of amino alcohol sphingosine + long chain fatty acid + monosaccharide unites .
* Glycolipids are important constituents of nervous tissue such as brain and the outer leaflet of the cell membrane
Cell membrane
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Steroids
* Steroid nucleus consists of four fused rings . * Sterols have steroid nucleus and a hydroxyl group
* Sterols are structural lipids present in the membranes of most eukaryotic cells.
*Cholesterol, the major sterol in animal, is both a structural component of membranes and precursor to a wide variety of steroids.
Cholesterol
Cholesterol, an amphipathic lipid, is an important component of membranes. It is the parent molecule from which all other steroids in the body, including major hormones such as the sex hormones, D vitamins,
and bile acids, are synthesized .
A B
C D1
2
3
45
6
7
8
910
11
1213
14 15
16
17
Steroid nucleus
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• Lipoproteins (blood transport molecules)• Glycoproteins (membrane structure)• Glycolipids (membrane receptors)
Combination of Biomolecules
• Lipoproteins :in membranes and transportation of materials
• Glycoproteins : antibodies, cell surface proteins
• Nucleoproteins : ribosomes
Protein Hybrids
Nucleic Acids
DNA & RNA
• Two types :• - Deoxyribonucleic acid (DNA)• - Ribonucleic acid (RNA)• Made of polymer of nucleotides joined
together by phosphodiester bond
DNA & RNA function• DNA carries and transmits the genetic
information . • RNA carry the genetic information from
nucleus to cytoplasm for protein synthesis .• RNAs are involved in most steps of gene
expression and protein biosynthesis.
Base + sugar
glycosidic bond
phosphoester bond
Nucleoside
Nucleotides
■ A nucleotide consists of a nitrogenous base (purine or pyrimidine), a pentose sugar, and one or more phosphate groups.
Nucleic acids are polymers of nucleotides, joined together by phosphodiester linkages between the 5’- hydroxyl group of one pentose and the 3’- hydroxyl group of the next.Nucleotides function as energy transfer molecules : ATP , Cyclic AMP , NAD & FAD
OH
OCH2
Sugar
H
HH
A NucleotideAdenosine Mono Phosphate (AMP)
OH
NH2
N
N N
N
BaseP
O
OH
HO OPhosphate
2’3’
4’
5’
1’Nucleotide
Nucleoside
H+
-
Pyrimidines
NH2
O
N
N NH
N
Guanine
N
N
Adenine
N
N
NH2
N O
NH2
N O
NH2
NCytosine
Purines
Uracil(RNA)CH3
N ON
O
NH
N ON
O
NH
Thymine(DNA)
Polynucleotide Formation
Dehydration reaction to form phosphodiester bond
Phosphodiester linkages in the covalent backbone of DNA and RNA. The phosphodiester bonds link successive nucleotide units. The backbone of alternating pentose and phosphate groups in both types of
nucleic acid is highly polar .
•The two strands are complementary & anti-parallel •Wound around each other in a rightward direction •stabilized by H-bonding between bases in adjacent
strands. •The bases are in the interior of the helix
•Purine bases form hydrogen bonds with pyrimidine .
DNA STRUCTURE
two polynucleotide chains are twisting around each other in the form of a double helix
Sugar phosphate backbone ofDNA
SUG
AR-PHO
SPHATE BACKBO
NE
H
P
O
HO
O
O
CH2
HOH
P
O
O
HO
O
O
CH2
H
P
O
OH
HO
O
O
CH2
NH2
N
N
N
N
O
O
NH2N
NH
N
N
N O
NH2
N
B A S E S
DNA
OH
P
O
HO
O
O
CH2
HO
O
H 2N
NHN N
N H
H
P HO
O
O
CH2
OO
N
O
H 2N
NH
H2O
H OH
P
O
HO
O
O
CH2
CH 3
O
O
HNN
H2O
5’Phosphate group
3’Hydroxyl group
5’Phosphategroup
3’Hydroxyl group
5 'C-G-A-T-T-G-C-A-A-C-G-A-T-G-C 3' | | | | | | | | | | | | | | |
3 'G-C-T-A-A-C-G-T-T-G-C-T-A-C-G 5'
Base Pair Rule •Adenine always base pairs with Thymine
(or Uracil if RNA)by two hydrogen bonds. •Cytosine always base pairs with Guanine
by Three hydrogen bonds.
NO
H
NO
N
NH Cytosine
H
O
NN
N
N
N
H
H
Guanine -+
+
+
-
-
Base PairingGuanine And Cytosine
CH3
N
O
N
ONH+
- ThymineN
NN
N
HN H
-
+Adenine
Base PairingAdenine And Thymine
Base PairingAdenine And Cytosine
NO
H
NO
N
NH Cytosine-
+
-
N
NN
N
HN
H
-
+
Adenine
Base PairingGuanine And Thymine
CH3
NO
N
O
NH+
- Thymine
H
O
NN
N
N
N
H
H
Guanine +
+
-
RNA
• Single strand of polynucleotides .• Purine bases are A & G , prymidines are C & U.
•In viruses it can carry out DNA role
*What are the differences in structure and function between DNA & RNA?