CHEM 30B  Dr. R. Rinehart            Amino Acid and Peptide Workshop 

►Using Netscape*, go to http://c4.cabrillo.cc.ca.us/chem30b/exercises/Chpt_19_033000/index.html
[or go to http://c4.cabrillo.cc.ca.us/chem30b/exercises/exerhome.html and select  Chapter 19].
There are nine exercises listed.
Do all except #7 and answer the questions asked on the worksheets.
[if you’re doing this outside class, their link to print your own worksheet isn’t working].
* I also was able to get this to work with the MS IE version of Chime, but it is not on the computers in PS-205..

HINT: Use the right-click pop-up menu to change the display as needed. 

1.   a.       Name each of the following amino acids. 
      b.       Give both the three-letter and one-letter abbreviations. 
      c.      Classify each of the amino acids according to the properties of its side chain:
                      neutral nonpolar, neutral polar, basic or acidic .

 2.a. Draw a complete structure [line structure, DO NOT show H, EXCEPT when on a heteroatom] for each of the following peptides. 

    b. Circle the peptide bonds within the peptide.  

   c. Label the N-terminal end and the C-terminal end. 

   d. Show the amino acid sequence using the one-letter [put in first open box in table below] and three-letter [place under drawing above] abbreviations.  

   e. Use the one-letter abbreviations to list all the other possible sequences for all tripeptides that could be made with the same 3 amino acids. Each amino acid can be used only once in each tripeptide.

3.       Enkephalin (from Latin, meaning "in the brain") is a naturally occurring peptide in the
     human body that reduces pain. It is found in various areas such as the brain, intestines,
     plasma, muscle and joint tissue. Name the individual amino acids starting at the N-terminal
     end and listing all the amino acid residues in order from left to right. For each residue, use
     its full name, three-letter and one-letter abbreviations. <this is just one of several different enkephalins> 

            N ________à ________à ________à _______à _______ C

4. Find and name the D-amino acid in each set of five amino acids.

5.    Find and name the D-alpha amino acid(s) in the following model set. There may be more than one of them. Note: some of these models are not alpha amino acids. [in which case, IGNORE them!]   

6.  Draw each of the following amino acids in the ionic form that predominates at pH 7. Show all charges.
            [Hint: they’ve pretty much done it for you already by protonating the amino groups and deprotonating the carboxyl groups – all you need to do is redraw in acceptable form [see example for 6.1  below] and show the charges!

7. For each of the following amino acids, draw the ionic form that predominates at the specified pH values.

 Show charges clearly. The models are in the nonionic form which does not exist in water. (Problem 7.3 and

 7.4 are more challenging than the others.)

8. Classify each of the following models using the categories: amino acid, dipeptide, tripeptide, steroid, phosphoglyceride, triglyceride, diglyceride, monosaccharide, disaccharide, or none of  these.

9.   The following reactions form dipeptides from amino acids.   

   a.       Identify X and Y for each reaction. (Use the three-letter code)

   b.       What is the other dipeptide that could be formed from each reaction? (Use the three-letter code)