380 Discussion Questions — Part D 



DISCUSSION QUESTIONS— PART D 



1. One of the smaller proteins whose structure is being intensively studied 

 is the enzyme ribonuclease. Describe its extraction and purification as well 

 as its enzymatic actions. What is known at present about its molecular 

 structure ? 



2. A fibrous protein which has been widely studied is the silk molecule. 

 What is known about large angle and small angle X-ray scattering by silk? 

 What is the present state of knowledge of the structure of silk ? 



3. Although many different lines of evidence have all been shown to be in 

 accord with the Crick- Watson double helix of DNA, no one, at the time of 

 writing this text, has been able to produce a satisfactory structure for RNA. 

 Describe the best current model of the RNA molecule. 



4. Electron spin resonance, discussed in Chapter 28, was used to locate 

 the Fe atoms in the myoglobin unit cell. Describe in detail how this was 

 accomplished. 



5. The enzyme fumarase catalyzes the hydration of fumarate to L-malate. 

 This reaction has been repeatedly studied by Alberty and his co-workers, 

 as well as several other scientists. Write suitable stoichiometric equations 

 and describe the corresponding kinetics for fumarase. 



6. The enzyme fumarase referred to in question 5 can be inhibited by 

 various compounds. What are some of these inhibitors? Describe their 

 action. What is learned about the action of fumarase by using these 

 inhibitors ? 



7. Mitochondria are small subcellular organelles found in almost all cells 

 (except bacteria and red blood cells). These organelles contain many 

 important enzyme systems. Describe the techniques and necessary pre- 

 cautions for isolating functional mitochondria. 



8. One action of the mitochondria is to phosphorylate ADP to ATP. How 

 is the P/O ratio defined? Discuss techniques for measuring the P/O ratio 

 with various substrates. 



9. The enzyme chains in intact mitochondria have been most clearly 

 demonstrated through the use of selective inhibitors. Describe how this can 

 be accomplished, giving specific examples of useful inhibitors. 



10. A large segment of the literature about enzyme action deals with the 

 role of — S — H groups which can be readily oxidized and reduced. In 

 which enzymes are — S — H groups important? How is this demonstrated? 

 What role do — S — H groups play in hemoglobin ? 



11. The enzyme invertase catalyzes the hydrolysis of sucrose, thereby 

 inverting the optical rotation of the solution. Describe the kinetics of this 

 reaction in the symbolism of calculus. 



