Topic Test 2: Fatty Acids and Molecular Structural Polarity       [see answers below]

True/False

1. The key chemical functional group, which helps define fatty acids and as hydrophobic is the phosphate?

2. An amphiphatic molecule is one which is insoluble water?

3. An unsaturated fatty acid has the same molecular shape as a saturated fatty acid?

Multiple Choice

4. The hydrophobic portion of a simple fat or lipid (a triglyceride molecule) is which end this fat/lipid?
   
a) the fatty acid end       b) the glycerol end       c) the phosphate end       d)  the alcohol end

5. The functional group which makes a portion of fatty acid molecule an acid is?
    a) a hydroxyl group                      b) a carboxyl group                     c)  a phosphate group

    d) a sulfhydryl group                    e)  an alcohol

6. The functional group which make a portion of a fatty acid hydrophilic is? 
    a) a hydroxyl group                      b) a carboxyl group                     c)  a phosphate group

    d) a sulfhydryl group                    e)  an alcohol

7.  A phospholipid molecule contains?
    a) a steroid                                  b) glucose                                    c) an amino acid         
   
d) two fatty acids                         e) three fatty acids

 

Short Answer/Problem Solving

7. Why was the occurrence of  amphiphatic molecules like phospholipids in plants, animals, and bacteria so important. Because phospholipids do not dissolve in water, but can form an interface with water, they make excellent structural components in which water-soluble species can be sequestered within an aqueous environment. It is just this amphipathic nature of phospholipids, i.e., containing both hydrophobic and hydrophilic groups, which makes then important in membrane structure.

8. Is a triglyceride or a phospholipid a polymer like starch or cellulose?

 

 

 

 

 

 

Topic Test 2:  Answers

1.  False.          It is the methyl group, CH3, which defines the hydrophobic nature of fatty acids.

2.  False.     An amphiphatic molecule is one with dual physical properties, that of containing both hydrophobic groups, which are insoluble in water, and hydrophilic groups, which are soluble in an aqueous environment?

3.  False.    An unsaturated fatty acid, contains a C=C bond within its structure which causes the chain of carbons in the fatty acid to have a kink in linear length, thereby bending the long chain hydrocarbon.  A saturated fatty acid in linear.

 

Multiple Choice

4.     a.     The hydrophobic portion of a simple fat, a triglyceride molecule, is the fatty acid end with it long chain of carbon and hydrogen atoms. 

5.     b.     The carboxyl group is the functional group which makes a fatty acid an acid is?

6.     c.      The functional group which make a portion of a fatty acid hydrophilic is the
                         electronegative  carboxyl group.

7.     d.      A phospholipid molecule contains glycerol, phosphate, an organic alcohol, and two fatty acids?

8. Why was the occurrence of  amphiphatic molecules like phospholipids in plants, animals, and bacteria so important. Because phospholipids do not dissolve in water, but can form an interface with water, they make excellent structural components in which water-soluble species can be sequestered within an aqueous environment. It is just this amphipathic nature of phospholipids, i.e., containing both hydrophobic and hydrophilic groups, which makes then important in membrane structure.

9. Technically, no. A polymer is a molecule made by the joining together, through strong covalent bonds, smaller molecular units called monomers. When these monomers are joined end-to-end, like links along a chain, a polymer is formed. Linear structure is a feature common to all polymers . Starch and cellulose qualify as polymers, but a triglyceride is not a linear molecule made of a repeating monomer.  While the same reaction which makes starch and cellulose, a condensation reaction makes a triglyceride, the fat is made of only 4 parts, one glycerol and 3 fatty acids, all of which can be of different molecular structure.  Starch and cellulose can be made of thousands of repeat glucose units.

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