Biochemistry lecture notes lipids

1. LIPIDS
Dr.B.RENGESH | M.Tech., Ph.D.
Associate Professor, Department of Pharmaceutical Technology,
Mahendra Engineering College (Autonomous),
Namakkal District, Tamil Nadu, India

2. v Lipids are organic compounds formed mainly from alcohol and fatty acids
combined together by ester linkage.
v Lipids are biological molecules that are insoluble in water but soluble in
nonpolar solvents (ether, chloroform, benzene, acetone).
v Lipids are the waxy, greasy, or oily compounds found in plants and animals.

3. v They are more palatable and storable to unlimited amount compared to
carbohydrates.
v They have a high-energy value (25% of body needs) and they provide
more energy per gram than carbohydrates and proteins but carbohydrates
are the preferable source of energy.
v Supply the essential fatty acids that cannot be synthesized by the body.
v Supply the body with fat-soluble vitamins (A, D, E and K).
v They are important constituents of cell membrane and nervous system.
BIOLOGICAL IMPROTANCE OF LIPIDS

4. v Stored lipids “depot fat” is stored in all animal cells act as
• A store of energy.
• A pad for the internal organs to protect them from outside shocks.
• A subcutaneous thermal insulator against loss of body heat.
v Lipids provide bases for dealing with diseases such as obesity,
atherosclerosis, lipid-storage diseases, essential fatty acid deficiency,
respiratory distress syndrome,
BIOLOGICAL IMPROTANCE OF LIPIDS

5. CLASSIFICATION OF LIPIDS
contain esters
contain 2 types of components (a
fatty acid & an alcohol)
contain > 2 types of components
(a fatty acid, an alcohol & others)

6. v a fatty acid is a carboxylic acid with a long aliphatic chain, which is either
saturated or unsaturated.
FATTY ACIDS

7. Properties:
• The long, nonpolar hydrocarbon tails of fatty acids are responsible for most
of the fatty or oily characteristics of lipids.
• The carboxyl (COOH) group is hydrophilic (polar) under basic conditions,
such as physiological pH (7.4)
• Fatty Acid Micelles
FATTY ACIDS
Micelles are important in the transport of insoluble lipids
in the blood

8. Characteristics:
• The chain length ranges from 4 to 30 carbons; 12-24 is most common.
• The chain is typically linear, and usually contains an even number of
carbons
• The many fatty acids which occur naturally arise primarily through
variation of chain length and degree of saturation
• There may be one double bond or many, up to six in important fatty acids.
FATTY ACIDS

9. Characteristics:
• When double bonds occur they are almost always cis. If there is more than 1
double bond, they occur at three-carbon intervals
FATTY ACIDS
e.g., -C=C-C-C=C-.
This is called
divinylmethane pattern.

10. • If without double bonds: Saturated Fatty Acids
• If with double bonds: Unsaturated Fatty Acids
o 1 double bond: Monounsaturated fatty acids
o 2 or more double bonds: Polyunsaturated fatty acids
FATTY ACIDS - Classification based on number of double bonds & Nomenclature

11. List of some Saturated Fatty Acids
Common Name Systematic Name
Structural
Formula
Lipid Numbers
Propionic acid Propanoic acid CH3CH2COOH C3:0
Butyric acid Butanoic acid CH3(CH2)2COOH C4:0
Valeric acid Pentanoic acid CH3(CH2)3COOH C5:0
Caproic acid Hexanoic acid CH3(CH2)4COOH C6:0
Caprylic acid Octanoic acid CH3(CH2)6COOH C8:0
Capric acid Decanoic acid CH3(CH2)8COOH C10:0
Myristic acid Tetradecanoic acid CH3(CH2)12COOH C14:0
Palmitic acid Hexadecanoic acid CH3(CH2)14COOH C16:0
Stearic acid Octadecanoic acid CH3(CH2)16COOH C18:0

12. List of some Mono-Unsaturated Fatty Acids
Common Name Chemical Name Lipid Numbers
Myristoleic acid cis-Tetradec-9-enoic acid 14:1 (n-5)
Palmitoleic acid cis-Hexadec-9-enoic acid 16:1 (n-7)
Oleic acid cis-Octadec-9-enoic acid 18:1 (n-9)
Elaidic acid (trans-oleic acid) trans-Octadec-9-enoic acid 18:1 (n-9)
11-Eicosenoic acid (gondoic acid) cis-Eicos-11-enoic acid 20:1 (n-9)

13. Common Name Lipid Numbers Chemical Name
List of some Omega-3 Poly-Unsaturated Fatty Acids
Alpha-linolenic acid 18:3 (n-3) all-cis-9,12,15-octadecatrienoic acid
Eicosapentaenoic acid 20:5 (n-3) all-cis-5,8,11,14,17-eicosapentaenoic acid
Docosahexaenoic acid 22:6 (n-3) all-cis-4,7,10,13,16,19-docosahexaenoic acid
List of some Omega-6 Poly-Unsaturated Fatty Acids
Linoleic acid 18:2 (n-6) all-cis-9,12-octadecadienoic acid
Gamma-linolenic acid 18:3 (n-6) all-cis-6,9,12-octadecatrienoic acid
α-linolenic acid 𝛄-linolenic acid

14. • Shorter fatty acids usually have lower melting points than longer ones
(stearic acid [18C] = 70ºC, palmitic acid [16C] = 63ºC)
FATTY ACIDS – Melting Property
• The cis-double bonds in
unsaturated fatty acids put an
inflexible “kink” in the carbon
chain, preventing the molecules
from packing together as tightly
as saturated fatty acids do.

15. • Animal fats and
vegetable oils are
esters composed of
three molecules of a
fatty acid connected to
a glycerol molecule,
producing a structure
called a triglyceride or
a triacylglycerol
STRUCTURE OF FATS AND OILS
TRIGLYCERIDES

16. • The fatty acids in a triglyceride molecule are usually not all the same;
natural triglycerides are often mixtures of many different triglyceride
molecules
TRIGLYCERIDES

17. • Fats are triglycerides that are solids at room temp.
– usually derived from animals & mostly saturated fatty acids
• Oils are triglycerides that are liquids at room temp.
– usually derived from plants or fish & mostly unsaturated fatty acids
TRIGLYCERIDES

18. TRIGLYCERIDES - Hydrolysis

19. TRIGLYCERIDES - Saponification
carboxylate salts
of the fatty
acids

20. TRIGLYCERIDES - Hydrogenation

21. • Waxes are simple lipids contain a fatty acid joined to a long-chain (12-32
carbons) alcohol
WAXES

22. • Waxes are insoluble in water, and not as easily hydrolysed as fats and oils.
They often occur in nature as protective coatings on feathers, fur, skin,
leaves, and fruits.
• Sebum, secreted by the sebaceous glands of the skin, contains waxes that
help to keep skin soft and prevent dehydration.
• Waxes are used commercially to make cosmetics, candles, ointments, and
protective polishes.
WAXES

23. • Phosphoglycerides are complex lipids that are major components of cell
membranes. Phosphoglycerides and related compounds are also called
phospholipids.
PHOSPHOGLYCERIDES

24. • The most abundant phosphoglycerides contain the alcohols choline,
ethanolamine, or serine attached to the phosphate group.
PHOSPHOGLYCERIDES - Aminoalcohols

25. • Phosphoglycerides that contains the aminoalcohol ‘choline’ are called
lecithins.
• The fatty acids at the first and second positions are variable, so there are a
number of different possible lecithins.
• They act as an emulsifying agent
PHOSPHOGLYCERIDES – (Aminoalcohol) – Lecithin

26. • Phosphoglycerides that contains the aminoalcohol ‘ethanolamine or serine’
are called lecithins.
• Cephalins are found in most cell membranes, and are particularly abundant in
brain tissue. They are also found in blood platelets, and play a role in blood-
clotting.
PHOSPHOGLYCERIDES – (Aminoalcohol) – Cephalin

27. • Sphingolipids are complex lipids that contain sphingosine instead of glycerol.
SPHINGOLIPIDS

28. • One important type of sphingolipds are the sphingomyelins.
SPHINGOLIPIDS - Spingomyelin
SPINGOMYELIN
• Sphingomyelins are found brain and nerve tissue,
and in the myelin sheath that protects nerves

29. • Sphingomyelins - a
bilayer that wraps
around nerve cell
axons
SPHINGOLIPIDS - Spingomyelin

30. • Glycolipids are sphingolipids that contain carbohydrates (usually
monosaccharides). They are also referred to as cerebrosides because of their
abundance in brain tissue
SPHINGOLIPIDS - Glycolipids
Cerebroside

31. • Most cell
membranes
contain about
60% lipids
(Amphipathic
Lipids) and
40% proteins.
• The fluid-
mosaic model :
Cell membrane
- Lipid bilayer
BIOLOGICAL MEMBRANES - Membrane Structure
membrane re-
forming @ damage

32. The Fluid Mosaic Model

33. STERIODS
• Steroids are classified as lipids because they are soluble in nonpolar solvents,
but they are non-saponifiable because the components are not held together
by ester linkages
• The basic steroid structure contains four fused rings
• There are three important types of
steroids:
1) Cholesterol
2) Steroid hormones
3) Bile salts

34. STERIODS - Cholesterol
• Cholesterol is the most abundant steroid in the body.
• it is manufactured in the liver.
• It is an essential component of cell membranes, and is a precursor for other
steroids, such as the bile salts, sex hormones, vitamin D, and the
adrenocorticoid hormones.
• There is apparently a correlation
between high levels of cholesterol in
the blood and atherosclerosis.

35. STERIODS – Steroid hormones
• Hormones, molecules that regulate the function of organs and tissues, come
in a variety of forms.
• Some, such as sex hormones and adrenocorticoid hormones, are steroids
• Sex hormones produced in the testes and ovaries regulate the production of
sperm and eggs and aid in the development of secondary sex characteristics
Eg.: testosterone, estradiol, progesterone
• Adrenocorticoid hormones are produced in the adrenal glands (located on
the top of the kidney). Eg.: Glucocorticoids - Cortisol and its derivatives,
cortisone and prednisolone

36. STERIODS
Sex hormones

37. STERIODS
Adrenocorticoid
hormones

38. STERIODS - Bile Salts
• Bile is a yellowish brown or green fluid produced in the liver and stored in
the gall bladder.

39. PROSTAGLANDINS
• Prostaglandins are cyclic compounds synthesized from arachidonic acid.
Like hormones, they are involved in a host of body processes, including
reproduction, blood clotting, inflammation, and fever.
• Prostaglandins have a wide range of biological effects:
– causing pain
– causing inflammation
– causing fever
– affecting blood pressure
– inducing labor (PGE2)

40. PROSTAGLANDINS
Carboprost
Dinoprostone