Lipids

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Chemistry B11
Chapter 21 Lipids
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Lipids
- Family of bimolecules. - They are soluble in
organic solvents but not in water (nonpolar).
1. Store energy fat cells
2. Chemical messengers find in nerve fibers and
hormones.
3. Parts of membranes not soluble in water
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Lipids
1. Simple lipids (Waxes, Fats Oils)
2. Complex lipids (Glycerophospholipids)
3. Steroid (Cholesterol steroid hormones)
4. Prostaglandins
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Fatty acids

• Fatty acids are
• Long-chain unbranched carbon attached to a
  carboxyl group.
• Typically 12-18 carbon atoms.
• Insoluble in water.
• Saturated or unsaturated.

Cis
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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 ?
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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.

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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.
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Carnauba
Beeswax
Coating
Jojoba
Lanolin from wool
lotions
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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.

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Esterification
glycerol three fatty acids
triacylglycerol
3H2O
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Triacylglycerols (Triglycerides)
Glycerol
Produced by esterification of glycerol (a
trihydroxyl alcohol).
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Triacylglycerols (Triglycerides)
Fat is a triacylglycerol that is solid at room
temperature. Made by more saturated fatty
acids. Meat, milk, butter and cheese (animal
sources).
Oil is a triacylglycerol that is liquid at room
temperature. Made by more unsaturated fatty
acids. Corn, cotton seed, safflower and
sunflower (plant sources).
Both are colorless, odorless, and tasteless.
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Hydrogenation

• 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.

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1- Hydrogenation
Ni
3H2 glyceryl
Trioleate (triolein)
glyceryl tristearate
(tristearin)
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2- Hydrolysis
Triacylglycerols are hydrolysis (split by water)
in the presence of strong acid or lipase
(digestive enzyme).

3H2O
3H

H or Lipase
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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
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Saponification

3NaOH
3

soap
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Glycerophospholipids
Choline
Polar part (polar head) and nonpolar part
(nonpolar tail)
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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
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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.

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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
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Steroids
Steroid hormones are Chemical messengers in
body Sex hormones Testosterone
androsterone in males Estrogen progesterone
in females
Testosterone (androgen) Male sex hormone
Estrogen Female sex hormone
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Lipoproteins
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.
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Lipoproteins
VLDL very-low-density lipoprotein
Triglycerides and Cholesterol
LDL low-density lipoprotein
Cholesterol
HDL high-density lipoprotein
Cholesterol
Chylomicrons
Triglycerides and Cholesterol
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Cell Membrane
Semipermeable nutrients can enter and waste
products can leave.
Fluid mosaic model