Transcript Document
Introduction
Lipids have a varied structure but all have the
following properties in common: Insoluble in water
Soluble in organic solvents
The three main groups of lipids are: Triglycerides
Phospholipids
Steroids
Lipids are important in cell membrane structure and
also as energy storage molecules and hormones.
Triglycerides
Triglycerides consist of a single glycerol molecule
and three fatty acids.
Fatty acids
Glycerol
Formation of Triglycerides
Triglycerides form by
condensation
(dehydration) reactions
between the hydroxyl
(OH) groups of the
glycerol and the
carboxyl (COOH) group
of three fatty acids.
Triglycerides are esters
being derived from an
alcohol and a fat.
Triglycerides (cont’d.)
Glycerol (blue) is an alcohol
derivative of glyceraldehyde and
has three hydroxyl groups. It acts
as the backbone of the structure.
Fatty acids (red) – there are more
than 70 types of fatty acid but they
all have long hydrocarbon tails
and a terminal carboxyl group
(COOH). The variety of fatty acids
determine the properties of each
triglyceride.
Structure of Triglycerides
The structure of triglycerides is varied due to the
variety of fatty acids. These molecules may be two
types which give rise to lipids with different properties: Saturated – these have no double C - C bonds e.g.
palmitic acid and stearic acid. Triglycerides
containing saturated fatty acids are very straight in
structure and pack closely together.
Unsaturated – have one or more double C - C
bonds e.g. oleic acid or linoleic acid. Lipids
containing unsaturated fatty acids are ‘kinked’ in
structure and cannot pack so closely together.
Triglycerides in Animals
Animals store their energy in
triglycerides with high melting
points which are solid at room
temperature.
These triglycerides
are referred to as fats.
result from reaction between
glycerol and a saturated
fatty acid e.g. stearic acid.
Triglycerides in Animals
Tips to help you remember. In animals triglycerides contain :
Single bonds only in fatty acids
Saturated fatty acids
Straight chained fatty acids
Stearic Acid is an example
Solid at room temperature – high melting point
Store energy
Source of metabolic water
Simply amazing as insulation and buoyancy aid
Triglycerides in Plants
Plants store their energy in
triglycerides with low melting
points which are liquid at room
temperature.
These triglycerides
are referred to as oils
result from reaction between
glycerol and an unsaturated
fatty acid e.g. oleic acid.
Triglycerides in Plants
Tips - to help you remember. In plants triglycerides are the
‘opposite of animals’ so learn the animals first and then go
through the list and change as follows
Double bonds in fatty acids
Unsaturated
Kinked chains
Oleic Acid is example
Liquid at room temperature – low melting point
Store energy
Triglycerides in Cells
Triglycerides are insoluble in
water because they have no
charge i.e. they have covalent
bonds. This causes them to
form droplets in the cytoplasm.
Functions of Triglycerides
Energy storage - triglycerides contain twice the
energy/gram of carbohydrates or proteins. During
aerobic respiration triglyceride is broken into 2C
portions which are fed into the Krebs cycle.
Source of metabolic water
– water is released on the
breakdown of triglycerides and
this property is used efficiently
is by desert mammals.
Functions of Triglycerides
(cont’d.)
Insulation – triglycerides are found in the blubber of
whales and other aquatic animals.
Buoyancy – aquatic animals use triglycerides to help
them float as they are less dense than water.