BCH 4053                        PRE-TEST  3   GROUP NAME _____________________
July 10, 1996

     This test is take-home and open book, and it is
intended that all members of the group contribute to
completing it.  Only one copy is to be submitted by
the group, and all members who participated should
sign their names below.  Test is due by 1:30 pm on
Monday, July 15.

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__________________________  __________________________

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Points


(4)  1.   Indicate in the blank whether each of the following pairs of sugars
          consists of anomers, epimers, or an aldose-ketose pair:

     ________  (a)  à-D-glucose and á-D-glucose

     ________  (b)  à-D-glucose and à-D-galactose

     ________  (c)  á-D-glucose and á-D-fructose

     ________  (d)  D-glyceraldehyde and L-glyceraldehyde



(5)  2.   Put a check by each of the following statements which are true.

          ____ Mannose is an epimer of glucose.

          ____ Galactose is an anomer of glucose. 

          ____ Sucrose is a á-glucoside.

          ____ L-Glucose is an epimer of D-glucose.

          ____ Ribose forms a furanose ring.



(4)  3.   What is the relationship between L-ribitol-1-phosphate and D-ribitol-
          5-phosphate?








(9)  4.   Draw the structure of:

          (a) an anomer of á-D-galactose     (b) an  enantiomer of á-D ribose







          (c) a disaccharide residue of chitin








(5)  5.   What structural feature makes a starch polymer helical and a
          cellulose polymer form a straight-extended chain?








(8)  6.   To illustrate the importance of tautomeric structure in the Watson-
          Crick base pairing, draw base pair structures showing how cytosine in
          the less stable tautomer can base pair with adenine, and how guanine
          in a less stable tautomer can base pair with thymine.

















(4)  7.   Explain why RNA is sensitive to hydrolysis in base, but DNA is not.









(8)  8.   Cytosine undergoes a slow chemical deamination.  
               (a)  What is the product of this reaction? 
               (b)  What effect would this product have on DNA if there were
                    not a repair system to remove the altered base?  
               (c)  How does the cell distinguish between this altered base and
                    the bases normally present in DNA?














(8)  9.   You have prepared DNA from two organisms isolated from the swamps of
          south Georgia, designated culture A and culture B.  DNA from
          culture A contains 24% G, while DNA from culture B contains 30% G. 
          Complete the following table for the expected composition of the
          other purine and pyrimidine bases.

                         %G         %A        %T        %C       Total

          Culture A      24        ____      ____      ____      100%

          Culture B      30        ____      ____      ____      100%

          DNA from which organism will have the higher melting temperature?




(6)  10.  Denaturing DNA by increasing the temperature is sometimes called
          "melting".  What changes occur upon melting in:
     
          (a) the secondary structure of DNA?





          (b) absorbance at 260 nm?





          (c) viscosity of the DNA solution?






(8)  11.  From the following DNA sequences, write the complementary sequence
          under it (in the 3' to 5' direction), and circle the bases of the
          resulting double stranded DNA which are palindromic sequences at
          least four base pairs in length.

          (a)  5'-GCTTCGAAC-3'          (b)  5'-CTACTACTA-3'
               3'-                           3'-




          (c)  5'-GCGCAACG-3'           (d)  5'-TTATTGCAAG-3'  
               3'-                           3'-






(12) 12.  Using data on free energies of hydrolysis from Table 13-6 of the
          text, calculate delta Go' for each of the following reactions and predict
          whether each will be spontaneous or non-spontaneous as written:

          (a)  phosphocreatine   +   ADP   ---->   creatine   +   ATP










          (b)  glucose   +    glycerol-1-     ---->    glucose-1-   +   glycerol
                               phosphate                phosphate




     






          (c)  glucose-1-phosphate ---->  glucose-6-phosphate










(8)  13.  Pyruvate kinase catalyzes the formation of ATP from phospho-
          enolpyruvate (PEP).  Calculate the [PEP]/[pyruvate] ratio necessary
          to produce a 50:1 ratio of [ATP]/[ADP] at equilibrium.



















(8)  14.  Combining data from tables 13-4 and 13-6, calculate the equilibrium
          constant for the following reaction:

           acetyl-CoA  +  ethanol   ---->  ethyl acetate +  CoA





















(3)  15.  What is the difference between delta Go and delta Go'?