Chem 451

HW, Lecture #18: High Energy compounds and Redox Reactions

HW: pg. 380 (study exercises; 3,4,5; problems; 2,4)

See back of book for answers to problems 2,4

Study Exercises:

3. Why is ATP a "high-energy" compound?

Three factors contribute to the high potential energy of the phosphoanhydride found in ATP. These are:

  1. electrostatic repulsion between the negative charges on the phosphate oxygen atoms.
  2. greater resonance stabilization of phosphate groups (hydrolysis products) than phosphoanhydride (Fig. 13-4).
  3. greater degree of H-bonding and therefore, greater solvation energy of hydrolysis products. (Phosphoanhydride has a lower solvation energy).

Click on ATP or go to

http://www.accessexcellence.org/AB/GG/ATP_ADP.html

 

4. Describe the ways an exergonic process can drive an endergonic process:

An exergonic reaction can "drive" an endergonic reaction if the two are coupled through a common intermediate. Coupled reactions will proceed if the sum of the change in free energy is negative

(D G1 + D G2 < 0).

5. What is the metabolic role of reduced coenzymes?

Reduced coenzymes carry electrons to the electron transport chain. Ultimately, ATP synthesis is coupled to the oxidation of glucose through reduced coenzymes.

Coupling Reactions in Biological Systems

Go to http://wunmr.wustl.edu/EduDev/LabTutorials/Cytochromes/cytochromes.html#ETCMovie

And scroll down to Coupling Reactions in Biological Systems