Page 106 - General Biochemistry

Fatty acids

• FAs are the “building blocks” lipids
• FAs do not generally exist free in vivo but are complexed to other molecules

depending on their function
• FA chain composed of an even number of C atoms with hydrogen atoms

along the length of the chain and at one end of the chain and a carboxyl
group (―COOH) at the other end.
• Fatty acids may be saturated or unsaturated, the term “saturated” means that
the hydrocarbon tails are saturated with hydrogen atoms and no C=C bonds,
just C-C and C-H bonds in the tail
• The number and placement of the double bonds affects the naming of the
FA, the chemical properties, and thus the properties of the lipid molecule into
which it is incorporated
• Fatty acids are of various lengths and degrees of unsaturation

Saturation of fatty acids
• Most FAs in animal tissues are saturated
• Most common FAs in animals and plants are C16 and C18
• Animal fats (triglycerides) are solid at room temp while most plant fats are

liquid (vegetable oils) this is due to differences in the degrees of
unsaturation of FA chains (most plant fats have at least one C=C)
• The Chain length and degree of unsaturation affects FA characteristics
• Short chain length and unsaturation lower FA melting temperature

– Introducing 1 cis DB lowers C18 melting point from 70° to 13°
– This enhances the fluidity of molecules that include these FAs

Fatty acids naming protocols:

1) Trivial (common) name:

The position of any unsaturated bonds is not obvious

Ex: oleic acid, palmitic acid

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