BCH 4053                        HOUR TEST 3          NAME _____________________
 July 19, 1996
          
Points

(8)  1.   What is the key structural difference between
          the two substances in each of the following
          pairs?

          (a)  amylose and amylopectin   





          (b)  D-glucose and D-mannose





          (c)  chitin and cellulose





          (d)  alpha-D-fructose and beta-D-fructose (draw the structures of these)






(4)  2.   Name the four aldotetroses.







(6)  3.   Sucrose is a (circle all that apply):

               hemiacetal      hemiketal            acetal

               ketal           reducing sugar       disaccharide


(6)  4.   Glycoproteins contain oligosaccharides with two types of linkages to
          the protein.  Describe the linkages and the amino acids involved.
          
          








(6)  5.   A furanose ring contains one oxygen and _____ (how many) carbons,
          while the other common ring structure found in sugars is called a 

          _________ ring, which contains one oxygen and _____ (how many)
          carbons?

(6)  6.   What are Chargaff's rules?







(8)  7.   Draw the structures of guanine and thymine in their proper tautomeric
          forms.











(8)  8.   Fill in the following blanks with A, B, or Z to indicate the form of
          DNA that fits the following descriptions.  More than one answer may
          apply.

          _______   Contains right-handed helix.

          _______   Contains left-handed helix.

          _______   Strands of helix are anti-parallel.

          _______   Strands are complementary, following Watson-Crick base
                    pairing rules. 


(6)  9.   Identify as nucleoside or nucleotide.

          adenosine ___________

          uridine   ___________

          adenylic acid   __________


(5)  10.  Circle the following DNA sequences which are potential recognition
          sites for a restriction endonuclease (i.e., which contain a
          palindromic sequence?):


          GAATTC          CCGG           GAGA       TCATCA         AGACTC


(8)  11.  Fill in the following table, describing the type and location of
          chemical bonds found in RNA.


     Bond formed between       Type of bond         Position of ribose

       uracil and ribose       ____________          ________________

       ribose and phosphate    ____________          ________________


(7)  12.  NAD+ is a nucleotide coenzyme which is a cosubstrate in many
          enzymatic reactions.

          (a)  What type of enzymatic reaction does NAD+ generally participate
               in?



          (b)  Show with a partial structure how the structure of NAD+ is
               altered during its reactions.







          (c)  NAD+ is a dinucleotide, meaning two nucleotides joined together. 
               What type of chemical bond joins the two nucleotides?





(6)  13.  Some phosphate compounds have "very high" negative free energies of
          hydrolysis, while some have "high" and some have "low" free energies
          of hydrolysis (also known as "group transfer potential").  Without
          having remembered specific values, you should have a sense of what
          compounds are in each class, and so you should be able to predict
          whether the following reactions would be spontaneous (with a negative
          delta Go' change) or non-spontaneous (with a positive delta Go'
          change).  Classify these reactions as spontaneous or non-spontaneous.

     (a)  glucose + phosphoenolpyruvate ---->  glucose-6-phosphate  +  pyruvate



     (b)  ATP  +   pyruvate   ---->   ADP  +  phosphoenolpyruvate



     (c)  glycerol-1-phosphate  +  ADP  ---->  glycerol  +   ATP

                      
                      
                      
                      Selected Free Energies of Hydrolysis

                Compound              delta Go' (kJ/mol)

            ATP (to ADP)               -30
            Glucose-1-phosphate        -21
            Glucose-6-phosphate        -14

Use the following constants:

     R = 8.315 x 10-3 kJ mol-1 deg-1;  T = 310 K;  ln x  =  2.3 log x 

(8)  14.  Calculate the [glucose-6-phosphate]/[glucose] ratio that can be
          obtained by hexokinase at equilibrium if the [ATP]/ADP] ratio is only
          0.2.

               glucose  +  ATP  ---->  glucose-6-phosphate  +   ADP
















(8)  15.  The "energy charge" of a cell refers to the relative amounts of ATP,
          ADP, and AMP.  Calculate the minimum work that must be done (i.e.
          delta G) to produce ATP from ADP in a cell with a high energy charge,
          where [ATP] = 1.85 x 10-3 M, [ADP] = 0.138 x 10-3 M, [Pi]=1 x 10-3 M.
          i.e., calculate delta G for the following reaction at these cellular
          concentrations:

                    ADP   +    Pi    ---->    ATP    +   H2O