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