The Chemical and Physical Structure of Protoplasm - 97 



11. What gases are usually present in proto- 

 plasm? How do these gases enter the cells? 

 Why are they important? 



12. Distinguish between organic and inorganic 

 compounds of the basis of 



a. occurrence in nature 



b. chemical composition 



c. molecular dimensions 



d. capacity to dissociate 



13. Describe a simple test that can be used to 

 differentiate between organic and inorganic 

 substances. Explain. 



14. Name lour different carbohydrate substances 

 and specify how each is important in various 

 cells. 



15. How are carbohydrates different from other 

 organic substances? 



16. To what extent is glucose used as a proto- 

 plasmic fuel? Explain, using the proper 

 chemical equation. 



17. Each chemical reaction represents a trans- 

 formation of matter that proceeds in ac- 

 cordance with the law of the conservation of 

 matter. Explain this statement using a specific 

 reaction to exemplify the discussion. 



18. What is the essential difference between an 

 exothermic and an endothermic reaction? 

 To what extent is it possible, by inspecting 

 an equation, to decide whether a reaction is 

 exothermic or endothermic? 



19. Distinguish between: 



a. decomposition and synthesis 



b. dehydration syntheses and other syn- 

 theses 



c. hydrolysis and other decompositions 



20. Specify the end products yielded by the com- 

 plete hydrolysis of: 



a. starch (and cellulose) 



b. maltose 



c. sucrose 



d. a true fat 



e. any simple protein 



f. any conjugated protein 



21. Provide at least one specific example, in each 

 case, of: 



a. monosaccharide sugars 



b. disaccharide sugars 



c. fatty acids 



d. amino acids 



22. As to chemical structure, how are amino 

 acids (a) similar to, and (b) different from 

 fatty acids? 



23. Explain the relation between: 



a. digestion and hydrolysis 



b. true fats and phospholipids 



24. As to the constituent atoms, how do proteins 

 differ from carbohydrates and fats? 



25. All complete proteins liberate the same amino 

 acids when fully hydrolyzed, and yet the pro- 

 teins of different animals and plants are 

 specifically distinctive. Explain. 



26. Show by formulas how an amino acid can 

 behave: (a) as an acid, and (b) as a basic 

 substance. 



27. Carefully explain: (a) the buffer action, and 

 (b) the amphoteric behavior of amino acids. 



28. Discuss the primary structure of protein 

 molecules. What types of chemical bonds de- 

 termine this structure? 



29. What is a hydrogen bond? Why are such 

 bonds important? 



30. What is meant by secondary and tertiary 

 structure in the protein molecule? By what 

 forces are these aspects of rtructure de- 

 termined? 



31. What may be the physiological significance 

 of the "folding" and "unfolding" of protein 

 molecules? What is a denatured protein? 

 Give an example. 



32. What is a conjugated protein? Name two 

 very important kinds. 



33. What is a nucleotide: a nucleoside? 



34. Name five organic bases present in various 

 nucleic acids. Which of these can be found 

 (a) in DNA only; (b) in RNA only; and (c) 

 in both DNA and RNA? 



35. Differentiate in as many ways as possible be- 

 tween DNA and RNA. 



36. Explain why DNA and RNA are very im- 

 portant in the cell. 



37. Assuming that the chemical composition of 

 protoplasm were fully known (which is far 

 from true), what other difficulties would have 

 to be surmounted to bring the "artificial syn- 

 thesis of protoplasm" within the realm of 

 possibility? 



38. Explain how the coarse, colloidal, and crys- 

 talloidal particles of protoplasm are to be 

 distinguished on the basis of: 



a. actual dimensions 



b. capacity to penetrate a cellophane 

 membrane 



c. capacity to penetrate the plasma mem- 

 brane 



