Exploring the Molecules of Life:  Performance Assessment

Let's pull the unit together by linking concepts together from the six activities.

1.     Cysteine (on the left below) is the only amino acid containing the -SH group.  Locate the group on cysteine. What is occurring in the cystine molecule on the right?

        The cystine molecule (right) contains a disulfide linkage, which is common in proteins where two cysteine molecules are opposite each other in a structure.  What level of structure does this help support in a protein?  1o      2o     3o     4o     Explain.

2.    In the process of digestion where substances are broken out by biochemical processes, what are the products for the following:

Starting materials Products

3.    The structure of beeswax is shown below.  What group of biological molecules do you think it will be similar to?  Why?

       What type of linkage occurs in beeswax? (hold the shift key down, click, and move the mouse to zoom)

4.    How are the structures of sucralose, an indigestible sugar substitute (on the left), and sucrose (on the right) related?

5.    Why can't the common enzymes that digest sucrose and fats, handle sucralose and olestra?

6.    For an amino acid glycine shown below, what has to happen for the neutral amino acid (on the left) to form the zwitterion on the right?

        What makes the zwitterion unusual?

7.   The table below lists four fatty acids with the same carbon chain length.

Fatty Acid Formula Melting Point, oC
stearic C17H35COOH 69
oleic C17H33COOH 13
linoleic C17H31COOH -9
linolenic C17H29COOH -17

         What is the difference in the four fatty acids?  Explain and support your answer based on the information in the table only.

8.  The structures of the three common amino acids in the zwitterion form are listed below.  Build a tripeptide using any order of the amino acids and compare it to another student.  If they are different, explain why.  You may want to use ball and stick models to build the amino acids and then link them.

 glycine      leucine    serine

9.    The sweetener aspartame has the structure given below.  It is composed of two common amino acids, one of which is modified by esterification.  What are the two amino acids?  Where is the ester on aspartame?  Here is a site for the 20 common amino acids showing them as Chime molecules.

10.    Using your knowledge of solubility behavior based on structure, predict the solubility of the following vitamins.  How are you going to make the decision of water or fat soluble?  Circle your choice in the table.

Vitamin Name Vitamin Structure Solubility
Vitamin A


water     fat
Vitamin B6


water     fat
Vitamin C

ascorbic acid

water     fat
Vitamin D2


water     fat
Vitamin E alpha-tocopherol water     fat
Vitamin K1 water     fat

11.    According to the DNA strand given below, what would the complementary strand be, comp-DNA?


According to the comp-DNA strand, what would the mRNA strand be?

What do you notice about the mRNA strand and the original DNA strand?

12.    On the graph below, which enzyme reaction A or B is faster?  Explain your choice.

Could the two curves just be due to a difference in the initial enzyme concentration, Eo?

Most of the structures on this page are from molecules collection available at the NSF-funded C4 Project at Cabrillo Community College.

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