http://www.ck12.org Chapter 3. Chemical Interactions
electrically charged ends, so it is attracted to the oppositely charged end of a phospholipid molecule. This end
of the phospholipid molecule is described as hydrophilic, which means “water loving.”- The other end of each phospholipid molecule is nonpolar and has no electric charge. This end of the phospho-
lipid molecule repels polar water and is described as hydrophobic, or “water hating.”
FIGURE 3.76
In theFigure3.76, the hydrophilic ends of the phospholipid molecules are on the outsides of the cell membrane,
and the hydrophobic ends are on the inside of the cell membrane. This arrangement of phospholipids allows some
substances to pass through the cell membrane while keeping other substances out. You can see how this works in
the video at the URL below.
http://www.beyondbooks.com/lif71/4b.asp
Summary
- Lipids are a class of biochemical compounds that living things use to store energy. Types of lipids include fats
and oils. - Both fats and oils consist of long chains called fatty acids, which may be saturated or unsaturated.
- Some lipids, called phospholipids, contain phosphorus as well as carbon, hydrogen, and oxygen. Two layers
of phospholipid molecules make up the cell membranes of living things.
Vocabulary
- lipid: Biochemical compound such as fat or oil that contains oxygen in addition to carbon and hydrogen and
is made up of long carbon chains called fatty acids.
Explore More
At the following URL, watch the animation about lipid structure and function. Then answer the questions below.