1. Fatty acids in biological systems typically contain an even number of carbon atoms, most commonly 16 or 18 carbons. 2. The melting point of fatty acids depends on the length of the carbon chain and degree of unsaturation, with shorter and more saturated chains having higher melting points. 3. Linoleic acid and linolenic acid are essential fatty acids that mammals cannot synthesize and must obtain from their diets.

3. The fatty acids in biological systems is usually contain an even number of carbon
atoms. The C 16 and C 18 are most common.
The melting point of the fatty acids depends on:
1. Length of chain (Short chain < Long chain)
2. Degree of unsaturation (Unsaturated < Saturated)(Cis<Trans)
Essential fatty acids:
Essential Fatty acids are those which are not synthesized by mammals. Mammals lack
enzymes that introduce the double bonds at carbon atoms beyond C9 in fatty acids.
Hence, Linoleic acid (18:2; ∆9, ∆12) and Linolenic acid (18:3; ∆9, ∆12, ∆15) are essential
fatty acids.

7. • Are triesters of fatty acids and
glycerol.
• Hydrophobic
• Non-Polar
• Major form of stored lipid
• Neutral lipid

8. They are of two types: Simple and mixed. Simple contain single kinds of fatty acids
and mixed triacylglycerols have two or more different types of fatty acid chains.
Triacylglycerol may be classified as fat and oil depending on the basis of physical state:
1. Fat: Solid at room temp., contain high portions of saturated fatty acids.
2. Oils: Liquid at room temp., contain high portions of unsaturated fatty acids.

10. Glycerophospholipids contain C16 or
C18 saturated fatty acid chain at C1
and C18 and C20 unsaturated fatty
acid at C2.

11. Nomenclature is:
PI(3)P means phosphoinositol-3- phosphate
PI(3,4)P2 : Phosphoinositol-3,4-bisphosphate
PI(3,4,5)P3: Phosphoinositol-3,4,5-trisphosphate
Similarly, rest of the nomenclatures are.
PI: involved in cell signalling cascades and
intracellular membrane trafficking through its
interactions with certain proteins in endosomes
PI(3)P: It plays a role in the processes of
internalization, sorting, and trafficking of
membrane proteins.
PI(4)P: is present in Golgi, PM, late endosomes,
lysosomes, secretory vesicles and
autophagosomes. It has a role in essential
nuclear processes, a function in the anterograde
transport from the trans-Golgi and the
retrograde transport from the Golgi to the ER; it
is also necessary for the formation of secretory
vesicles in the Golgi.

12. Phosphatidic acid: Intermediate in synthesis of
triglycerides and phospholipids.
Phosphotidylcholine: Nerve Impulse transmission
and maintain surface tension (adhere to the inner
surface of lungs)
Phosphotidylethanolamine: Clotting factor III
thromoplastin.
Phosphotidylinositol: Secondary messanger for
oxytocin and vasopressin.
Plasmogens: Present in myelin sheath formation,
Cardiac muscles and platelet aggregation.
Cardiolipids: Present in inner mitochondrial
membrane have antigenic properties and isolated
from heart muscles.
Glycerophospholipids: Lipoproteins, bile, lung
surfactant.
PAF: Released from phagocytic blood cells in
response to various stimuli (platelet aggregration,
edema, hypotension).

13. Waxes are esters of fatty acids and long chain
alcohols.
Formed by esterification of long chain fatty
acids and high molecular weight monohydroxy
alcohols (C14 to C36).
Best animal was is Beeswax containing an ester
of palmitic acid with alcohol triacontanol-
Triacontanoylpalmitate)

14. In glycosphingolipids head group contains one or
more sugars connected directly to the –OH at C1
ceramide moiety.
Do not contain phosphate.
It can be:
Cerebroside: Have monosaccharide linked to
ceramide.
Globoside: Have oligosaccharide linked to
ceramide.
Gangliosides: Contain complex oligosaccharide as
their polar head with one or more residues of N-
acetylneuraminic acid.

17. Sphingolipids are a class of lipids containing a backbone
of sphingoid bases, a set of alpiphatic amino alcohols that
includes sphingosine.
Present in PM and first discovered in brain extracts in the
1870s
These compounds play important roles in:
Signal transduction and signal cascades
Cell recognition
structural function
serve as the site of adherence of extracellular proteins
Mediator of stress responses
Involved in autophagy, necrosis and apoptosis
Sphingomylein is present in the Mitochondria and is
involved in the respiratory functions.

20. Cardiolipin is an acidic lipoprotein that is
abundant in the inner mitochondrial
membrane and is required for normal
respiratory chain enzyme activity.
Two phosphatidic acid moieties
connect with a glycerol backbone in
the center to form a dimeric structure.
In most animal tissues, cardiolipin
(CL) contains 18-carbon fatty alkyl
chains with 2 unsaturated bonds
on each of them.

21. It are complex derivatives of triterpenes.
Composed of four fused rings called steroid nucleus.
Is characterized by a hydroxyl group at C3.
Cholesterol is a waxy substance stored as fatty acid ester
in the body.
It acts as precursor for biosynthesis of steroid hormones
and bile salts.
In plants: Stigmasterol, sitosterol and campesterol.
In fungi: Ergosterol.

22. Eicosanoids acts as short range messenger.
Eicosanoids (Leukotrienes and Prostaglandins) are
derived from C20 fatty acid arachidonic acids.
In prostaglandins is C20 fatty acid with carbon
atoms 8 to 12 comprise a cyclopentane ring. It was
first identified in human semen. All cells except
RBC produce prostaglandins.
Leukotrienes are hydroxyl fatty acid derivatives of
arachidonic acid and do not contain ring. Involved
in chemotaxis, inflammation and allergic
reactions.