1. Lipids To model how triglycerides are formed.
To understand how fatty acids can vary.
To predict the structure of a phospholipid.
To assess how the properties of phospholipids are biologically important.

2. The Nature of Lipids
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, steroids
and 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

3. A Fatty Acid Glycerol The Components of Fats & Oils Carboxylic
Glycerol is a 3-carbon alcohol molecule
Fatty acids are composed of hydrocarbon chains of
varying length with a methyl group at one end and a
carboxylic acid group at the other
A Fatty Acid
Carboxylic
acid group
Hydrocarbon
chain
Methyl
group
Glycerol

4. Formation of a Triglyceride
GLYCEROL
THREE
FATTY ACID
MOLECULES
-3H2O Condensation Reaction A
TRIGLYCERIDE
Ester bond

5. Mono & Diglycerides Monoglycerides; a single fatty acid molecule
bonds with the glycerol
molecule
Diglycerides;
two fatty acid molecules
bond with the glycerol
molecule

6. Phospholipids are Diglycerides
Glycerol
Fatty acid
Fatty acid
Phosphate group
CHCOO 2
Fatty acid
Phosphate
Polar end of the molecule
(hydrophilic) – attracts water OR

7. Phospholipids OR

8. Phospholipids Polar phosphate head (hydrophilic)
The phosphate –containing end
of the phospholipid molecule is
soluble in water, while the
hydrophobic fatty acid tails
orientate themselves in positions
away from a watery medium
Polar phosphate head
(hydrophilic)
Hydrophobic fatty acid
(lipid) tails
The bipolar nature of
phospholipids allows these
molecules to form bilayers that
form a major component
of cell membranes

10. water Cholesterol molecules are located between the PHOSPHOLIPID
tails of the phospholipid
molecules where they
serve to stabilise the
membrane
PHOSPHOLIPID
BILAYER
water
These cholesterol molecules
are also classed as LIPIDS
although they belong to
a very different sub - group
known as STEROIDS
phospholipid
bilayer of cell
membrane
cholesterol stabilising
the membrane

11. of the group, is built around a characteristic four-ringed skeleton
Steroids
CHOLESTEROL
Cholesterol is one of the most common steroids and, like all other members
of the group, is built around a characteristic four-ringed skeleton
Apart from its role as a stabilising component of cell membranes, cholesterol
is also the precursor for the synthesis of many important steroid hormones

12. hormones testosterone,
Steroids
TESTOSTERONE
PROGESTERONE
The steroid sex
hormones testosterone,
progesterone and
oestrogen are
synthesised from
cholesterol

13. Saturated & Unsaturated Fatty Acids Unsaturated fatty acid:3 2
Saturated fatty acid
General formula for a
saturated fatty acid 2 n 3
Double bond
Unsaturated fatty acid:
less saturated with
hydrogen atoms

14. Make these 2 fatty acid chains.

15. Fatty Acids at room temperature.

16. Fatty Acids at room temperature.
Vegetable fat (olive oil)
Animal Fat (butter)

17. Saturated & Unsaturated Fatty Acids
All the linkages between the carbon atoms in the hydrocarbon chain are
single bonds: these fatty acids are therefore saturated with hydrogen atoms
Saturated fats consist entirely of saturated fatty acids and are the
animal fats
Saturated fats are solid at room temperature

18. Saturated & Unsaturated Fatty Acids at which the lipid melts
Unsaturated fats contain unsaturated fatty acids and thus possess a number
of double bonds
In general, the greater the number of double bonds, the lower the temperature
at which the lipid melts
The large number of double bonds in vegetable oils accounts for their liquid state

20. Answers A- triglycerides B- glycerol C- polyunsaturated D- two
E- hydrophobic

21. Answers
Triglyceride- 3 fatty acids and no phosphate group. It is non-polar.
Phospholipid- 2 fatty acids and a phosphate group. Hydrophilic head and hydrophobic tail.

22. Answer Lipids provide x2 energy as carbohydrate when oxidised.
If fat is stored, the same amount of energy can be provided for less than half the mass.
It is therefore lighter as a storage product- an advantage in motile organisms.

23. Summary 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.

24. 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.

25. Lipids To model how triglycerides are formed.
To understand how fatty acids can vary.
To predict the structure of a phospholipid.
To assess how the properties of phospholipids are biologically important.