Page 110 - The Manga Guide to Biochemistry
P. 110
Yikes! So many Cs...it’s like a nightmare report card!
Palmitic acid CH3(CH2)14COOH When there is a double
Stearic acid CH3(CH2)16COOH bond inside the molecule,
Linoleic acid CH3(CH2)4(CH=CHCH2)2(CH2)6COOH we write it like this.
α-linolenic acid CH3CH2(CH=CHCH2)3(CH2)6COOH
Arachidonic acid CH3(CH2)4(CH=CHCH2)4(CH2)2COOH
Certain fatty acids have double bonds between the carbon atoms in the middle of the
molecule, as you can see in this figure.
HH HH
CC CC
HH HH
A carbon atom has four However, in some cases, two
“arms,” and usually a arms are used to bond a
separate atom bonds
with each arm. carbon with another atom.
This is called a double bond.
Carbons that are double bonded are called unsaturated carbons, and fatty acids that
have unsaturated carbons are called unsaturated fatty acids.
Unsaturated fatty acids don’t solidify as easily, remaining as liquid at lower
temperatures than saturated fatty acids, so they are often included as a component
of cell membranes (that is, phospholipids) for which flexibility is important.
So...if there are a lot of double bonds, fatty acids are harder to solidify?
That’s right. Double bonds can create kinks, which prevent the unsaturated fatty
acids from forming a stable solid. This means that the melting point of fatty acids
differs significantly depending on the number of carbon atoms and the number
of double bonds between those carbon atoms.
96 Chapter 3
