© SSER Ltd.
Dec 23, 2015
© SSER Ltd.
Lipids are a diverse collection of substances that have a range of different functions in living systems
Lipids are compounds that serve both as structural and nutrient substances
The lipid group includes fats and oils, waxes, steroidsand phospholipids. These molecules have a low solubility in water
but a high solubility in solvents such as ethanol and chloroform
Fats & oils are formed from molecules of glycerol
and fatty acids
The Nature of LipidsThe Nature of Lipids
GlycerolMethylgroup
Carboxylicacid group
A Fatty Acid
Hydrocarbonchain
Glycerol is a 3-carbon alcohol molecule
Fatty acids are composed of hydrocarbon chains ofvarying length with a methyl group at one end and a
carboxylic acid group at the other
The Components of Fats & Oils The Components of Fats & Oils
Double bond
Unsaturated fatty acid:less saturated with
hydrogen atoms
32 3
Saturated fatty acid
General formula for asaturated fatty acid
2 n 3
Saturated & Unsaturated Fatty AcidsSaturated & Unsaturated Fatty Acids
ATRIGLYCERIDE
-3H2O Condensation Reaction
Ester bond
GLYCEROLTHREE
FATTY ACIDMOLECULES
Formation of a TriglycerideFormation of a Triglyceride
OR
hydrophilic phosphategroup
Gl y
cero
l
Fatty acid
Fatty acid
Phosphate
hydrophobic tails
Gl y
cer o
l
Fatty acid
Fatty acid
Phosphate
PhospholipidsPhospholipids
Polar phosphate head(hydrophilic)
Hydrophobic fatty acid(lipid) tails
The phosphate-containing endof the phospholipid molecule is
soluble in water, while thehydrophobic fatty acid tails
orientate themselves in positionsaway from a watery medium
The bipolar nature ofphospholipids allows these
molecules to form bilayers thatform a major component
of cell membranes
PhospholipidsPhospholipids
PHOSPHOLIPIDBILAYER
water
water
phospholipidbilayer of cellmembrane
cholesterol stabilisingthe membrane
Cholesterol moleculesare located between thetails of the phospholipidmolecules where they serve to stabilise the
membrane
These cholesterol moleculesare also classed as LIPIDS
although they belong toa very different sub-group
known as STEROIDS
Fats & oils are made up of carbon, hydrogen and oxygen atoms.
The building blocks (monomers) of fats and oils are glycerol & fatty acid molecules.
Fats & oils are TRIGLYCERIDES. Three fatty acid molecules bond to each glycerol
molecule by CONDENSATION REACTIONS. The bonds formed from these condensation reactions
are called ESTER BONDS. Fats & oils are chemically similar but physically
different. Fats are solid at room temperature whereas oils are
liquid.
SummarySummary
Monoglycerides & diglycerides also form when glycerol and fatty acids bond by condensation reactions.
Monoglycerides form when only ONE FATTY ACID bonds with a glycerol molecule.
Diglycerides form when TWO FATTY ACIDS bond with a glycerol molecule.
Phospholipids are DIGLYCERIDES. Phospholipids form when TWO FATTY ACIDS and a
PHOSPHATE group bond to a glycerol molecule. The phosphate end of the molecule is hydrophilic
(water-loving) and the two fatty acids tails are hydrophobic (water-hating).
Phospholipids are a major structural component of cell membranes.
Steroids such as cholesterol, oestrogen and progesterone also belong to the class lipids.