Transcript LIPIDS

LIPIDS
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Hydrophobic, non-polar molecules
Used for energy storage, building
membranes and chemical signalling
Four main types: fats, waxes, steroids and
phospholipids
1) FATS
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Store more energy per gram than
carbohydrates, BUT their energy is not as
easily accessible.
Used for: insulation, cushioning internal
organs...
Most common fats in
plants and animals are
the triacylglycerols
(aka triglycerides)
which consist of a
glycerol backbone and
3 fatty acids.
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Glycerol is an alcohol, while the fatty acids
are an acidic carboxyl group combined with a
long hydrocarbon chain (16C to 18C long).
H
H
C
OH
H
C
OH
H
C
OH
H
Glycerol
Fatty Acid
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Saturated fatty acids have no double bonds
in the hydrocarbon chain, solid at room
temperature (animal fats, butter, lard).
Unsaturated fatty acids do have double
bonds in the hydrocarbon chain, liquid at
room temperature, known as oils (plant fats).
HYDROGENATION
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...is the process of adding hydrogen
molecules to a plant oil in order to make it
saturated and therefore solid (margarine
/shortening).
The process is done using an enzyme and
hydrogen gas.
Can lead to TRANS FATS
ESTERIFICATION
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When glycerol combines with each fatty acid a
condensation reaction (dehydration synthesis)
occurs.
An acid reacting with an alcohol produces an ester
linkage, hence this process is called esterification.
2) PHOSPHOLIPIDS
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Make up the majority
of the cell membrane.
Contain a glycerol
molecule combined
with two fatty acids
and a highly polar
phosphate group.
Phosphate head is
hydrophillic while the
fatty acid tail is
hydrophobic.
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In a cell membrane the phospholipid bilayer
makes it impossible for polar molecules and
charged molecules to pass due to the
hydrophobic center.
That is why there are protein channels in the
cell membrane to allow these types of
molecules to pass through.
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/phoph.gif
http://www.smartdraw.com/examples/content/Examples/Heal
thcare/Microbiology_&_Biochemistry/Phospholipid_BiLayer_L.jpg
3) STEROLS (Steroids)
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Highly hydrophobic
Four fused hydrocarbon rings with many
different functional groups
Cholesterol is a steroid, which is important in
cell membranes to maintain their fluidity.
 It can also be
dangerous as
ingested
cholesterol can
lead to blocking
of the arteries.
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Other important steroids include the sex
hormones (testosterone, estradiol and
progesterone).
4) WAXES
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Hydrophobic fatty acid chains attached to
ring structures or alcohols.
Very pliable solids.
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Used by animals
and plants as
waterproofing
agents (cutin in
the cuticle of
plants, beeswax,
feathers of birds).
http://www.lipidlibrary.co.uk/Lipids/waxes/image004.gi