190 A CONCEPTUAL INTRODUCTION TO BIOENERGETICS 



living systems. It is recommended that he take the appetizers, References 13 

 and 14, before he starts the full courses offered by References 2, 6, 10, or 15. 



PROBLEMS 



7-1 : If a man submits to a diet of 2500 Cal/day, and expends energy in all forms to a 

 total of 3000 Cal/day, what is the change in internal energy per day? 



If the energy lost was stored as sucrose (390 Cal/100 g), how many days 

 should it take to lose 1 lb? (Ignore water loss for this problem.) 

 7-2: (a) From the following heats of formation at 25° C, compute the heat of com- 

 bustion (i.e., the "fuel value") of d-glucose. Give the answer in Cal/mole 

 and Cal/gram. 



\H f 



All elements (Na,0,, etc.) 



CO, -94.4 Cal/mole 



HX> -64.4 



C 6 H 12 6 (d-glucose) -279.8 



(b) Given the heat of combustion of sucrose to CO, and H 2 to be 1349 

 Cal/mole, compute the heat of formation from the elements. 

 7-3: (a) From the values given for AH and AFfor any two reactants tabulated in 

 the text, calculate the entropy change per mole, 

 (b) For each of these two cases, calculate the standard emf of the reaction. Are 

 these values for pH = 7? 

 7-4: Given the fact that the standard emf 's for the redox systems methylene blue and 

 maleate-succinate are respectively 0.05v and 0. 1 v, at the physiological pH of 7, 

 calculate the standard free energy of reaction (at pH = 0). {Note how important 

 it is to define the pH, or alternatively that the living system keep its pH con- 

 stant.) 

 7-5: (a) Using the Nernst equation, plot E as afn of pH for: 



(i) 1/2 H 2 — H + + e" -0.42 v 



(ii) succinate — * fumarate 4- 2H + 2e~ -0.00 v 



(iii) 4 OH" — O, + 4e" + 2H 2 +0.80 v 



(iv) Cu — Cu ++ + 2e"atpH = 7. +0.36 v 



(b) If E Q = 0.50 v and n = 2, plot E as fn of per cent oxidation from to 



100 per cent. 



REFERENCES 



1. Clark, VV. M., "Topics in Physical Chemistry," 2nd ed., The Williams and 



WilkinsCo., Baltimore, Md., 1952. 



2. Clark, W. M., "Oxidation-Reduction Potentials of Organic Systems," The 



Williams and Wilkins Co., Baltimore, Md., 1960. 



3. Fruton,J. S., and Simmonds, S., "General Biochemistry," John Wiley & Sons, 



Inc., New York, N. Y., 1953. 



4. Glasstone, S., "Thermodynamics for Chemists," D. Van Nostrand Co., Inc., 



New York, N.Y., 1947. 



