1. Chemistry B11
Chapter 15
Lipids

2. Lipids - Family of biomolecules.
- They are not defined by a particular functional
group, thus they have a variety of structures and
functions.
- They are soluble in organic solvents but not in water (nonpolar).
- They contain many nonpolar C—C and C—H
bonds and few polar bonds resulting in their water
insolubility.

3. Lipids Lipids 1. Store energy: fat cells
2. Chemical messengers: find in nerve fibers and hormones.
3. Parts of membranes: insoluble in water

4. Lipids 1. Simple lipids: (Waxes, Fats & Oils)
Store energy, insulation
Cell membrane
Chemical messenger
Pain, fever, inflammation
2. Complex lipids (Glycerophospholipids)
3. Steroid (Cholesterol & steroid hormones)
4. Eicosanoids

5. Fatty acids Fatty acids are:
Long-chain unbranched carbon attached to a carboxyl group.
Typically carbon atoms.
Insoluble in water.
Saturated or unsaturated.
Cis

6. Saturated and unsaturated Fatty acids
Saturated fatty acids are solids at room temperature.
Packed together  Maximum London dispersion forces
Unsaturated fatty acids are liquids at room temperature.
Can not pack together  London dispersion forces 

7. Fatty acids
The human body is capable of synthesizing most fatty acids from
carbohydrates or other fatty acids.
Humans do not synthesize sufficient amounts of fatty acids that
have more than one double bond.
More than one double bond fatty acids are called essential fatty acids and they must be provided by the diet.

8. Waxes are found in many plants and animals (or humans).
In plants, they help prevent loss of water and damage from pests.
In humans and animals, provide waterproof coating on skin and fur.
Wax is an ester of saturated fatty acid and long chain alcohol.
Long-chain alcohol
Fatty acid
Ester bond

9. Waxes
For example, shown below is the formation of spermaceti wax, isolated from the heads of sperm whales.
Acid

10. Beeswax
Carnauba
Coating
Jojoba
Lanolin from wool
lotions

11. Triacylglycerols (Triglycerides)
Triacylglycerols are:
Fats and oils (are stored in the body).
Triesters of glycerol.
Produced by Fischer esterification.
Formed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids.

12. Esterification
glycerol three fatty acids triacylglycerol
+ 3H2O
Acid

13. Triacylglycerols (Triglycerides)
CH2 CH OH
Glycerol G L Y C E R O
Fatty acid
Produced by esterification of glycerol (a trihydroxyl alcohol).

14. Triacylglycerols (Triglycerides)
Fat: is a triacylglycerol that is solid at room temperature.
Made by more saturated fatty acids (Saturated triacylglycerols).
Meat, milk, butter and cheese (animal sources).
Oil: is a triacylglycerol that is liquid at room temperature.
Made by more unsaturated fatty acids (Unsaturated triacylglycerols).
Corn, cotton seed, safflower and sunflower (plant sources).
Both are colorless, odorless, and tasteless.

15. Hydrogenation _C=C_ + H2 → _C_C_
Hydrogen adds to the double bonds of unsaturated fats (using transition
metal catalyst such as Ni).
Melting point is increased.
- Liquid oils are converted to semisolid fats.
_C=C_ + H2 → _C_C_ Ni H

16. 1- Hydrogenation Ni + 3H2 glyceryl Trioleate (triolein)
glyceryl tristearate
(tristearin)

17. 2- Hydrolysis
Triacylglycerols are hydrolysis (split by water) in the presence of strong acid
or lipase (digestive enzyme).
+ 3H2O O H C 2 +
3HO
H+ or Lipase

18. 3- Saponification
Is the process of forming “soaps” (salts of fatty acids).
Is the reaction of a fat with a strong base (NaOH).
Splits triacylglycerols into glycerol and the salts of fatty acids.
With KOH or the oils that are polyunsaturated gives softer soaps (liquid soaps).
Name of soap gives the source of the oil.
Like coconut or avocado soap

19. 3- Saponification (Basic Hydrolysis)
+ 3NaOH
Heat + 3
“soap”
Salt of fatty acid

20. Soaps
Hydrophobic part: nonpolar
Hydrophilic part: polar (remains in contact with environment)

21. Soaps
When soap is mixed with dirt (grease, oil, and …), soap micelles “dissolve” these nonpolar, water-insoluble molecules.

22. Glycerophospholipids
Fatty acid
phosphate
Amino
alcohol N
CH3
HO – CH2 _ CH2 + P O O_
Choline
Polar part (polar head) and nonpolar part (nonpolar tail)
Interact with both polar and nonpolar substances.
1. Most abundant lipids in cell membranes (semipermeable).
2. Combine with less polar triglycerides and cholesterol to make them soluble.

23. Steroids Steroids have: A steroid nucleus which is 4 carbon rings.
Attached groups that make the different types of compounds.
No fatty acids.
steroid nucleus

24. Cholesterol Cholesterol: Is the most abundant steroid in the body.
Insoluble in water (need a water soluble carrier).
Has methyl CH3- groups, alkyl chain, and -OH attached to the steroid nucleus.

25. Cholesterol Cholesterol: Is obtained from meats, milk, and eggs.
Is synthesized in the liver from fats, carbohydrates and proteins.
Is needed for cell membranes, brain and nerve tissue, steroid hormones, and Vitamin D.
Clogs arteries when high levels form plaque.
No cholesterol in vegetable and plants.
At artery clogged by cholesterol plaque
Gallstones form in gallbladder

26. Testosterone (androgen)
Steroids
Steroid hormones are:
Chemical messengers in body
Sex hormones
Testosterone & androsterone in men
Estrogen & progesterone in women
Testosterone (androgen)
Male sex hormone
Estrogen
Female sex hormone

27. Lipoproteins Spherical particles Polar surface and nonpolar inner
Triacylglycerols
Water-soluble form of lipids
(soluble in blood)
Spherical particles
Polar surface and nonpolar inner
Transporting lipids through the bloodstream to tissues where they are stored,
Used for energy, or to make hormones.

28. VLDL: very-low-density lipoprotein
Lipoproteins
VLDL: very-low-density lipoprotein
Triglycerides and Cholesterol
LDL: low-density lipoprotein (bad Cholesterol)
Cholesterol
HDL: high-density lipoprotein (good Cholesterol)
Cholesterol
Recommended levels are: HDL > 40 mg/dL, LDL < 100 mg/dL, total serum cholesterol < 200 mg/dL.
Chylomicrons
Triglycerides, phospholipids, cholesterol, and proteins
Transport dietary lipids from intestines to the body.
Liver
Fat storage
cells
Heart and
muscles
LDL
VLDL
HDL
Energy
Intestine
and
elimination

29. Cell Membrane
Nonpolar
Polar
Phospholipid
bilayer
Carbohydrate
Semipermeable: nutrients can enter and waste products can leave.
Fluid mosaic model