AP BIOLOGY

BIOCHEMISTRY

POLAR AND NONPOLAR MOLECULES

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Which of the following describes the characteristics of a phospholipid?
A
Polar phosphate head and two nonpolar lipid tails
B
Nonpolar phosphate head and two polar lipid tails
C
Polar phosphate head and two polar lipid tails
Explanation: 

Detailed explanation-1: -1: A phospholipid consists of a head and a tail. The “head” of the molecule contains the phosphate group and is hydrophilic, meaning that it will dissolve in water. The “tail” of the molecule is made up of two fatty acids, which are hydrophobic and do not dissolve in water.

Detailed explanation-2: -Phospholipids are amphiphilic. They have a polar head and two hydrocarbon tails, which are nonpolar. The phospholipids that make up the cell membranes of plants, bacterial or animal cells often have fatty acids tails. Of these two fatty acid tails one is unsaturated (contains double bonds) and the other is saturated.

Detailed explanation-3: -This makes phospholipid molecules have a hairpin shape. The head of the hairpin is very polar and therefore likes to associate with water (it is hydrophilic), while the two fatty acid chains (the “tails") are very non-polar and tend to avoid water (hydrophobic) and associate with other hydrocarbon chains.

Detailed explanation-4: -The main component of the cell membrane is a phospholipid bi-layer or sandwich. The heads (the phospho part) are polar while the tails (the lipid part) are non-polar.

There is 1 question to complete.