Page 109 - The Manga Guide to Biochemistry

Fatty acids

Fatty acids are a source of energy, and they can become phospholipids, which are a
raw material for creating cell membranes. If there were no fatty acids, humans could
not live.

Wow, really? That’s surprising! And I thought they were the enemy.

First, let’s look at the structure of fatty acids. Although they can be constructed by
connecting a few to several dozen carbon (C) atoms together, the fatty acids that are
in our bodies always contain 12 to 20 carbon atoms.

H HHHHH O

CH CH CH CH CH CHC (CH3(CH2)12COOH)

H3C H C H C H C H C H C H C OH

H HHHHH

Carboxyl

group

Fatty acid

At the farthest end of that long chain (which is called a hydrocarbon chain) is a
structure called a carboxyl group (-COOH).

Since only hydrogen (H) atoms are attached to each of the carbon atoms,
the fatty acid does not mix easily with water. It lacks hydroxyl groups (OH), which
saccharides have (see page 61 for information about saccharides).

Oh, I get it, like oil and water. So tough to mix!

Some fatty acids are made in our bodies. For instance, excess carbohydrates are
converted into palmitic acid. Two fatty acids, linoleic and a-linolenic acid, are essen-
tial, which means that they are necessary for good health and cannot be synthesized
by humans. On the other hand, stearic acid and arachidonic acid cannot be synthe-
sized but are not essential to good health either. All these fatty acids contain over
16 Cs!

Biochemistry in Our Everyday Lives 95