Chem 30B Name ________________________

3rd hour exam Seager Chpts 8 - 11 please print

May 14, 2001 107 points

A. Fill in the blanks:

[2] 1. The DNA sequence CCGCTATTAGCT codes for a peptide containing _ __ (give a number) amino acid residues.

[2] 2. Before a cell can split into two daughter cells it must first its DNA.

[2] 3. Anticodons are located on what specific kind of molecules?

[2] 4. When a triglyceride is hydrolyzed what functional group is broken down ?

[2] 5. The RNA that carries the information which determines the primary structure of a polypeptide chain is called

[2] 6. A newly discovered hormone is found to be fat soluble. It is most likely a member of the specific family of chemicals called .

[2] 7. Hydrolysis of a protein involves a change in which level of protein structure?

[2] 8. The most common lipid in our diet is _____________________ .

[2] 9. The only covalent bond (linkage) in the 3∞ structure of a protein is ______________

[2] 10. A beta pleated sheet is held together by _____________________________

[2] 11. The most important difference between a coenzyme and a prosthetic group is

[4] 12. The flow of information in molecular biology (sometimes known as the "central dogma") can be represented by ---> --->

[4] 13. The codon UGU is complementary to the triplet on DNA and to the anticodon .

14. [2] a. The principal kind of chemical compound in biological membranes is

.

[2] b. The other two kinds of compounds also present in these membranes are

& /34

Part B 1. [5] Explain why many amino acids have more than one codon.

2. [6] Small carboxylic acids and amines are liquids at room temperature, but even the smallest amino acids are solids. Explain what aspect of amino acid structure is responsible for this difference.

3. [6] Draw the structure of a basic amino acid in a neutral solution (pH 7), clearly showing its charges.

4. [8] Draw the structure of a soap molecule and briefly explain its cleansing action.

5. [8] Describe the interaction of an allosteric enzyme and its modulator. Draw and label a simple sketch to support your description.

/33

6. [9] Which one of the forces holding together the tertiary (3∞) structure of a protein is the main one involved in each of the following situations? Briefly explain each choice.

a. The activity of an enzyme is measured at pH 6 and at pH 8. The measured activity is much greater at 8 than at 6.

b. A reducing agent is used as part of a permanent wave .

c. A protein is denatured by putting it into a non-polar solvent like hexane.

7. List and briefly describe three substantially different chemical structures in which hydrogen bonding plays a significant role. Draw a simple diagram or chemical structure to illustrate each example.

a. [5]

b. [5]

c. [5]

/24

8. [10] Explain in detail why and how a small change in the pH of a solution can cause a major change in the activity of an enzyme.

9. [6] Draw a simple sketch (diagram) of an RNA nucleotide. Label each part.

/16