Organic Macromolecules
 The
Lipids
What are lipids
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Lipids are what are commonly
referred to as fats. Waxes
and oils are also lipids.
Lipids are an essential part of
the human diet.
Typically our diet should
consist of about 30% fat.
Unfortunately, most Americans
consume closer to 40%
Why do you think people like
food with so much fat in it?
What do we need lipids for
anyway?
The major function of lipids in our body is
the storage of energy.
 Lipids contain a lot of energy in the form of
chemical bond energy, just like
carbohydrates do.
 One gram of fat holds twice as much
chemical bond energy than one gram of
carbohydrates.
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Lipid functions continued
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Lipids are also important in the
structure of the cell
membrane,(it is a phospholipid
bilayer)
Steroid hormones
(Testosterone, estrogen and
progesterone).
Transporting important
molecules throughout the body
(Cholesterol)
Elements present in lipids
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Just like the carbohydrates,
lipids consist of carbon,
hydrogen and oxygen, that’s it,
nothing else.
Unlike carbohydrates, there
isn’t a specific ratio of
Hydrogen to Oxygen.
However it will always, always,
always be greater than 2:1.
Do you recall what other
element(s) are found in amino
acids?
Lipid monomers
Just like proteins and carbohydrates, lipids
are large molecules made up of smaller
molecules. The building blocks of lipids
are
 1 molecule of glycerol, and (usually) 3 fatty
acids.
 Phospholipids are made of glycerol, 2 fatty
acids and 1 phosphate molecule.
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Lipid Building blocks
Glycerol is considered an alcohol.
 Every molecule of glycerol is exactly the
same.
 It has 3 carbons, 3 OH groups, and 5
hydrogens.
 Molecular formula is C3H5(OH)3
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Structural formula of Glycerol
Fatty acids
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While there are different types of fatty acids,
they all have some things in common.
They consist of long chains of carbon and
hydrogen, and they all contain a carboxyl
functional group. It is this carboxyl group that
gives the fatty acid it’s acidic properties.
Can you remember where else we saw a
carboxyl group?
Saturated versus Unsaturated.
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Not all fats are good for you. The bad ones
consist of saturated fatty acids. These fatty
acids are completed saturated with hydrogen
atoms, and have no double bonds between
carbon atoms. Stearic acid is saturated.
Unsaturated fatty acids are not completely
saturated because they contain a double bond
between carbon atoms somewhere in the chain.
Oleic acid is unsaturated.
Polyunsaturated fats contain two or more double
bonds between carbons. Linoleic acid is
polyunsaturaed.
Structural formula of fatty acids
Why are saturated fats bad?
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It is because the form LDL (Low density
lipoproteins).
These molecules transfer cholesterol, but tend to
deposit this cholesterol in your arteries, causing
blockages.
This can lead to heart disease.
Unsaturated fatty acids form HDL (High density
lipoproteins). These carry cholesterol to the
liver, where it needs to be.
LDL’s are sometimes referred to as bad
cholesterol and HDL’s are referred to as good
cholesterol.
Dehydration Synthesis
Just like Proteins and Carbohydrates,
lipids are formed through the process of
dehydration synthesis.
 The general equation is
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1 Glycerol + 3 fatty acids 
1 Lipid + 3 molecules of water.
Animation of Dehydration
Synthesis
http://www2.nl.edu/jste/lipids.htm
Hydrolysis
As we learned with proteiNs and
carbohydrates, anything that is created by
dehydration synthesis can be broken apart
by hydrolysis.
 The equation for the hydrolysis of lipids
would then be.
1 Lipid + 3 molecules H20 
1 glycerol + 3 fatty acids
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Trans-fatty acids
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The natural shape of lipids are what organic
chemists refer to as the cis configuration.
However lipids can also be made to take the
trans configuration.
In order to increase the shelf life and to make
unsaturated fats solids at room temperature,
unsaturated fats are changed into transfats
through a process called partial hydrogenation.
Partial hydrogenation
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In this process, an
unsaturated or
polyunsaturated fatty acid has
addition hydrogen atoms
added to it, breaking some of
the double bonds between
carbons.
This changes the shape of the
molecule, and raises the
melting point of the fat to over
110 degrees fahrenheit.
It also extends the shelf life of
the lipid.
What is the big deal about
transfats?
Because they have a higher melting point
than normal cis fats, they stay solid in your
relatively cool body. It makes it nearly
impossible to “burn” this fat.
 Since the structure is changed, the
enzymes, which are proteins remember,
aren’t as effective at breaking them down
into their building blocks.
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Foods with transfats
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Here are some foods
you may want to
avoid or at least cut
back on.
cakes
 cookies
 margerine
 french fries
 potato chips
When in doubt, read the
label.
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Health risks and Transfats
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Coronary heart
disease.
Alzheimer’s disease.
Cancer.
Diabetes.
Liver disfunction.
Infertility.