LIPIDS
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are naturally occurring hydrophobic molecules
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are heterogenous group of compounds related
to fatty acids
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make up about 70% of the dry weight of the
nervous system
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are crucial for the healthy functioning of the
nerve cells
GENERAL CHARACTERISTICS
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made up of Carbon, Hydrogen, and Oxygen
include fats and oils, waxes, phospholipids, and
steroids
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relatively insoluble in water
•
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soluble in non-polar solvents, like ether,
chloroform, methanol, and acetone
TYPES
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have high energy content and are metabolized
to release calories
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act as electrical insulators, they insulate nerve
axons
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include animal fats which are saturated and
solid at room temperatures
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include plant fats which are unsaturated and
are liquid at room temperatures
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melting point depends on the length of the
chain of the constituent fatty acid and the
degree of unsaturation
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bad conductors of heat
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need to be emulsified to be absorbed by the
intestinal wall
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hydrolyzed by the enzyme lipases to yield fatty
acids and glycerol
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in the year 1943 Bloor proposed the following
classification of lipids based on their chemical
composition
SIMPLE LIPIDS OR HOMOLIPIDS
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are the esters (fragrant organic compound) of
fatty acids with various alcohols
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include fats and oils (triglycerides), and waxes
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fat is solid at ordinary room temperature and oil
is liquid
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waxes are the esters of fatty acids with high
molecular weight
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examples: beeswax, paraffin wax, etc.
COMPOUND LIPIDS OR HETEROLIPIDS
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are esters of fatty acids with alcohol and
possess additional groups
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include phospholipids and glycolipids
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phospholipids are compound containing fatty
acids and glycerol in addition to a phosphoric
acid and other substituent
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phospholipids can be phosphoglycerides,
phosphoinositides and phosphosphingosides
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phosphoglycerides are major phospholipids,
they are found in membranes
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example: lecithin and cephalins
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phosphoinositides play important roles in lipid
signaling, cell signaling and membrane
trafficking
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phosphosphingosides are commonly found in
nerve tissue
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example: sphingomyelins
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glycolipids are the compounds of fatty acids
with carbohydrates and contain nitrogen but no
phosphoric acid
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terpenes are produced by a variety of plants,
particularly conifers and by some insects such
as termites or swallowtail butterflies
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carotenoids are organic pigments that are
produced by plants and algae, as well as several
bacteria and fungi
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are carboxylic acids consisting of a hydrocarbon
chain and a terminal carboxyl group, especially
any of those occurring as esters in fats and oils
FUNCTIONS
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storage compounds
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important component of cell membranes
structure
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regulate membrane permeability
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serve as source for fat soluble vitamins like A, D,
E, K
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act as an electrical insulators to the nerve fibers
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act as cellular metabolic regulators such as
prostaglandins and steroid hormones
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act as signaling molecules
DERIVED LIPIDS
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are the substances derived from simple and
compound lipids by hydrolysis
includes fatty acids, alcohols, monoglycerides
and diglycerides, steroids, terpenes and
carotenoids
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steroids do not contain fatty acids, they are
nonsaponifiable and are not hydrolyzed on
heating
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are widely distributed in animals, where they
are associated with physiological processes