General ---------Biology----------------------------------------------------- ------------------Online--------------------------------------- Ch. 8 Membrane Structure and Function

Phospholipids are similar to fats, but they have two fatty acids rather than three, and the glycerol has a phosphate group.  In Figure 5.6 from your text, shown below, one of the fatty acids is saturated (straight), and the other is unsaturated (crooked).  As you recall, saturated fats (lard, butter) are solid at room temperature, and unsaturated fats (corn oil) are liquid at room temperature.  By increasing the percentage of unsaturated fatty acids, cells can make their membranes more fluid.  This is a survival strategy for many plants living in cold climates.

The image below shows the carbon and hydrogen atoms in the fatty acid tails.  In this image both fatty acids are saturated. 

Which atom is  the most electronegative?
a.  carbon     b. hydrogen    c. oxygen    d. phosphate 

Which bonds are most likely then to be polar covalent bonds?
a. C-H    b. C-O

Where are the oxygen, and therefore the polar covalent bonds, located?
a.  glycerol head
b.  fatty acid tail

Which end of this molecule will be hydrophilic?
a.  glycerol head
b.  fatty acid tail

The above molecule can be drawn in simplified form as shown below.

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1. Membrane Structure