2. Lipids
• Chemically diverse group of compounds
✓ low solubility in water
✓ high solubility in nonpolar solvents
• Play diverse biological function
✓ energy storage
✓ structural component
emulsifying agents-
Some lipids, like bile salts, act as emulsifying agents. They help break down fat globules
into smaller droplets, allowing for better digestion and absorption of dietary fats in the
intestines. This is especially important in the digestive process.
✓ Hormones- steroid hormones and ecosianides
✓ intracellular messengers
• represent highly reduced forms of carbon
➢ largely hydrocarbon in nature
➢ metabolic energy storage
• Lipids
• Hydrophobic
✓Totally insoluble in water
• Amphiapathic
✓Sparingly soluble in water
2
3. Classificatien ef lipids
1. Simple lipids
➢ Esters of fatty acids with various
alcohols FA + Glycerol
FA + HMW alcohol
✓ Fats
✓ Wax
2. Complex lipids
3
➢ Containing groups in addition to an alcohol and a fatty
acid
a) Phospholipids
✓ Containing phosphoric acid residue
b) Glycolipids
✓ Containig sphingosine and carbohydrate
c) Lipoproteins
✓ Conjugated with protein
3. Derived lipids
➢ precursors or derived products of
lipids
✓ Fatty acids
✓ Glycerol
✓ Ketone bodies-used by brain,
skeletal muscle, heart and kidney.
4. Fatty
acids
• carboxylic acids with hydrocarbon
chains
• Differ in
1) Chain length
a) SCFA
b) MCFA
c) LCFA
2) Level of unsaturation
a) Saturated FA
➢ all carbon–carbon bonds are single bonds
b) Unsaturated FA
➢ one or more double bonds (cis) in the HC
chain
✓ Monounsaturated FA
✓ Polyunsaturated FA
3) Structure
a) Linear-energy storage, cell membrane signaling
like ecocyanides
b) Branched- in membrane structure
c) Cyclic- prostaglandin,/ arachidonic acids
derivative, used in inflammation regulation,
immiune response, and blood clotting
4
5. • Physical property of FA determined
by
✓ Chain length
✓ Degree of unsaturation
➢ Longer chain
➢ fewer double
bonds
reduced
solubility high
melting point
5
6. femenclature ef FAs
1. Systematic
➢ Based on
✓ Carbon number
✓ Level of unsaturation
2. Common name
➢ Based on
✓ the source from which the FA was first
spotted
3. Shorthand notation
➢ Provides
SH
✓ No of carbon
atoms
✓ No of unsaturation
✓ Sites of
unsaturation
STR
SYS COM Mp
t
6
7. Essential fatty acids
• not synthesized by mammals
➢ necessary for normal growth and life
➢ must be obtained from diet
✓linoleic acid
✓Linolenic acids
• Arachidonic acid
➢ Synthesized from linoleic acid
➢ Serve as precursor for the synthesis of
eicosanoids
Linoleic acid Linolenic acid Arachidonic acid 7
8. Acylglycerels
• Glycerol with one or more fatty acids
➢ attached through ester linkages
✓ MAG
✓ DAG
✓ TAG
• Triacylglycerol
➢ Major energy reserve
✓ Rich in highly reduced carbon
➢ Provides insulation
a) Simple
✓ Same FAs
b) Mixed
✓ Different FAs
✓ Unsaturated FAs usually found at
C-2
8
10. hesphelipases
• enzymes that cause the breakdown of
phospholipids
✓ Phospholipase A1: removes FA on C1
✓ Phospholipase A2: removes FA on C2 (arachidonic
acid)
✓ Phospholipase C : cleaves phosphate-glycerol
bond.
✓ Phospholipase D : cleaves phosphate-head
group bond.
11
11. Ether glycerophospholipids
• Posses an ether linkage at C-
1
12
➢ Platelet activating factor (PAF)
✓ C-2 contains acetate
✓ More water soluble
➢ Plasmalogens- have importance
in fluidity
✓ C-1 contains cis-α,β-unsaturated
FA
➢ Head groups
✓ choline
✓ ethanolamine
✓ Serine
12. Sphingelipids
13
• Contain sphingosine as a
backbone
➢ Attach fatty acids by amide bond
✓Ceramide
➢ Membrane component
➢ Constituents of lipoproteins
• Function
✓ Structure
✓
✓ Signal transduction
• Sphingomyelin
➢ Phosphosphingolipid(phospho
diester bond)
➢ Used in nerve myelination
➢ Formed by esterification of
ceramide with
✓Phosphorylcholine
✓Phosphorylethanolamine
13. Glycesphingelipids
14
• Ceramide with one or more sugar residues
a) Neutral glycospingolipids
➢ Contain uncharged sugar residue
➢ Cerbosides
✓ Contain single molecule of
✓ Glc
✓ Gal
b) Acidic glycosphingolipid
i. Ganglosides
✓ Ceramide esterified with three or more
sugar
➢ containing Sialic acid
➢
14. ii. sulfatides
✓ Contain sulfate esterified with
Gal
✓ Involved in
➢ Neuronal cell
differentiation
➢ Myelin formation
15
16. 2) Steroids
is
of
➢ Are derivatives of
triterpenes
➢ Composed of four fused
rings
✓ Cholesterol
➢ Is amphiapathic
➢ Component of cell
membrane
➢ Precursor for the synthes
✓ Steroid hormones like sex
hormone and
coricosteroids
✓ Vitamin D
✓ Bile salts
17
17. Lipepreteins
• Molecular complexes used for lipid transport in
circulation
• Structure
➢ Spherical
✓ Neutral lipid core
➢ TG,CE
✓ Surface monolayer amphiapathic lipids and proteins
➢ PL, Cholesterol, Apo proteins
18
18. Classificatien ef lipepreteins
• Classified based on density
➢ total lipid content is inversely correlated with the density
of the lipoproteins
✓ Lipid/
protein
✓ Lipid/
protein
Low density
High
density
19
19. Functien ef lipepreteins
1) Chylomicron
➢ Largest and lipid rich
➢ Transport lipid from intestine to adipose and
muscle
➢ Have apo protein B-48, C-II
2) VLDL
➢ Synthesized in the liver
➢ Transport lipid to tissues
➢ Contain apo proteins B-100, C-II, E
3) LDL
➢ Have high concentration of cholesterol and CE
➢ Provide cholesterol to peripheral tissue
➢ Have apo protein B-100
4) HDL
➢ Secreted from liver and intestine
➢ Reverse cholesterol transport
➢ Have apo proteins C-II,E,A
20
20. Bielegical membranes
• Are external boundaries of cells
➢ regulate the molecular traffic across that
boundary
➢ forms discrete compartments in the cell
➢ Help in cell to cell recognition
• They are flexible
➢ Shape changes
• They are selectively permiable
➢ Impermeable for polar molecules
➢ Permeable to non-polar molecules
• Composed of
✓ Proteins
✓ Polar lipids
✓ Glycoproteins and glycolipids
➢ Proportion will differ based on the type of
membrane
21
21. Fluid mesaic medel ef
membranes
• Is a bilayer of phospholipid
where
✓ Non polar
regions
✓ Polar head
groups
face the
core face
outward
✓ Proteins are embedded in the bilayer
➢ Hydrophobic interaction
• Individual lipid and protein units are free to
change
➢ Non covalent interaction
22
22. • Wembrane preteins
➢ Two types
a) Integral proteins
➢ Firmly associated with the membrane
➢ Hydrphobic interaction
➢ Removed by detergents, organic solvents
b) Peripheral proteins
➢ Found on one face of the bilayer
➢ Electrostatic bond and hydrogen bond
➢ Removed by mild treatment with ionic
solution
23
Editor's Notes
#2:Sparingly Soluble in Water:
Certain types of lipids, such as cholesterol, are sparingly soluble in water but can still interact with other lipids or proteins to form structures like lipid rafts or membranes.
They store more energy per gram than carbohydrates or proteins because they are highly reduced forms of carbon (they contain long carbon chains).
Lipids like phosphoinositides and certain fatty acids act as intracellular messengers, helping to transmit signals inside cells. For example, diacylglycerol (DAG) and inositol trisphosphate (IP3) are involved in signaling pathways that control processes like cell growth, differentiation, and metabolism.
Highly Reduced Forms of Carbon:
Lipids are considered highly reduced forms of carbon because they contain many hydrogen atoms bonded to carbon atoms. This high reduction state makes lipids an excellent source of metabolic energy when oxidized (broken down for energy).
Cholesterol enters in membrane structure and is used for synthesis of some hormones, vitamin D 3 and bile acids.
Supply the body with fat-soluble vitamins (A, D, E and K).
They are important constituents of the nervous system.
#3:Glycolipids Glycolipids :, carbohydrate carbohydrate + sphingosine sphingosine, but not phosphoric acid nor glycerol.
They are products of hydrolysis of simple and compound lipids and/or their derivatives that still possess the general characteristics of lipids.
Fatty acids, monoglycerides and aldehydes. 2. Alcohols including glycerol. 3. Sterols, steroids and hormonal derivatives of vit. D. 4. Eicosanoids (prostaglandins, leukotrienes and thromboxanes). 5. Ketone bodies.
#4:While fatty aid oxidation, ketone bodies are produced in the liver from fatty acid.
Medium-Chain Fatty Acids (MCFAs): Carbon Chain Length: 6 to 12 carbon atoms May be beneficial for weight management. They can cross the blood brain barrier.
Long chain fatty acids- Require more complex digestion and absorption processes.
Major components of cell membranes and stored body fat. Play essential roles in various physiological functions. These require chylomicrons for transport in the body.
Polyunsaturated fatty acid They can not be synthesized in the human body (due to lack of enzymes that can form more than one double bond)
Functions OF PUFA : 1. Useful to prevent atherosclerosis. 2. Prostaglandin & eicosanoids are synthesized 3. They participate in structure of all cellular and subcellular membranes and the transporting plasma phospholipids. 4. Essential for skin integrity, normal growth and reproduction. 5. Important role in blood clotting. 6. Important in preventing and treating fatty liver. 7. Important role in health of the retina and vision. 8. They can be oxidized for energy production.
#5:Short chain FA less 6 carbon have low temperature, high solublity, low MP due to small vaanderwals force.
Unsaturated fatty acids are liquid and have low melting point.
Hydrophobic Dominance: As the hydrocarbon chain of a fatty acid gets longer, the nonpolar portion of the molecule becomes increasingly dominant. This significantly outweighs the relatively small polar influence of the carboxyl group.
These have one double bond in their hydrocarbon chain. The double bond creates a "kink" in the chain, preventing tight packing. This results in weaker Van der Waals forces and a lower melting point (liquid at room temperature, like olive oil)
#6:Melting Point increase with Length Melting Point decrease with Unsaturation
Basic Structure:
The name starts with the number of carbon atoms in the chain, followed by the suffix depending on saturation.
Saturated fatty acids: End in “-anoic”.
Unsaturated fatty acids: End in “-enoic” (for one double bond), “-dienoic” (for two double bonds), etc.
Example 1: Saturated Fatty Acid
Stearic Acid: C18:0
Systematic Name: Octadecanoic acid.
Explanation: This fatty acid has 18 carbon atoms and no double bonds (saturated).
Example 2: Monounsaturated Fatty Acid
Oleic Acid: C18:1
Systematic Name: Octadec-9-enoic acid.
Explanation: This fatty acid has 18 carbon atoms and one double bond at position 9 (from the carboxyl group).
#7:There is no an enzyme that desaturate saturated fatty acid beyond carbon number 9. and most essential fatty acids are PUFA.
Gamma linoleic and arachidonic acid are semi-essential.
#8:Highly reduced means more hydrogen so more capacity of energy production.
the term 'most reduced' refers to a molecule that has the highest number of carbon-hydrogen (C-H) bonds and the lowest number of carbon-oxygen (C=O) bonds.
Simple Acylglycerol: All the fatty acids attached to glycerol are the same. For example, tristearin (three molecules of stearic acid attached to glycerol) is a simple triacylglycerol.
Mixed Acylglycerol: The fatty acids attached to glycerol are different. For example, 1-palmitoyl-2-oleoyl-3-stearoylglycerol is a mixed triacylglycerol
#9:Fatty acid attached to C- 1 and C-2 are hydrophobic and phosphate attached with C3 is polar.
#11:This enzyme acts specifically on the sn-1 fatty acyl group (the fatty acid attached to the first carbon of the glycerol backbone).
The product of this hydrolysis reaction is a lysophospholipid (a phospholipid with only one fatty acid attached) and a free fatty acid.
#12:Ether Linkage at C-1:
In ether glycerophospholipids, the fatty acid at the C-1 position of the glycerol backbone is attached via an ether bond instead of the usual ester bond.
This ether bond (–O–) forms a stronger and more stable linkage compared to the ester bond, which contributes to the unique properties of these lipids.
Platelet Activating Factor (PAF):
Platelet-activating factor (PAF) is a well-known ether glycerophospholipid that plays an important role in inflammatory responses and cell signaling.
PAF has a special structure where the C-2 position contains an acetate group (–COOCH₃) instead of a typical fatty acid. This acetate group makes PAF highly bioactive, and it is involved in platelet aggregation, immune cell signaling, and vasodilation.
Plasmalogens are abundant in heart tissue, brain tissue, and muscle cells, where they play a role in membrane structure and possibly in protecting cells from oxidative damage.
#13:They are important components of cellular membranes, particularly in the nervous system. Sphingolipids play key roles in membrane structure, signal transduction, and cell communication.
Sphingosine contains both an amine group (–NH₂) and a hydroxyl group (–OH) on the backbone,
Sphingomyelin is the most abundant sphingolipid in the plasma membrane, particularly in the myelin sheath of nerve cells
#14:Sugar Residues: The defining feature of glycosphingolipids is the attachment of one or more sugar molecules to the hydroxyl group at the C-1 position of the ceramide. These sugars can include glucose (Glc), galactose (Gal), and more complex sugar structures.
#16:Tertraterpene contain 8 isoprene units, these includes carotenoids like beta carotenes which is a precursor to vitamin A and gives many fruits and vegetables their orange color ad red color.
#17:Role in Cell Membranes: Cholesterol is an essential component of cell membranes, where it modulates membrane fluidity. It maintains the structural integrity of the cell membrane and prevents the membrane from becoming too rigid or too fluid.
Vitamin D: While also a steroid, vitamin D functions as a prohormone that is involved in calcium and phosphorus metabolism.
Bile salts emulsify fats in the intestine, breaking them down into smaller droplets so that they can be further digested by enzymes. They also aid in the absorption of fat-soluble vitamins (A, D, E, K).
#18: Triglycerides (TG) are the main form of stored fat in the body and are a major source of energy.
Cholesteryl esters (CE) are formed when cholesterol is esterified with fatty acids. These are more hydrophobic than free cholesterol and help with the packing of lipoproteins
#22:The hydrophobic tail of the phospholipids and proteins in the membrane interact through hydrophobic interactions, which help maintain the structural integrity of the bilayer.
#23:Peripheral proteins involved in cell signaling, enzyme activity or maintain structure of membrane through cytoskeletal connection. Example cytoskeleton.