GENERAL BIOLOGY 



tion by heat? (2) Coagulation by chemicals. To 5 cc. of the 10 

 per cent albumin add a few drops of 3 per cent copper sulphate. 

 Try also strong nitric acid and sulphuric acid, allowing a drop or 

 two to run down the side of the test tube. Try also 95 per cent 

 alcohol. (3) Test urine for albumin as follows: a. Boil 10 cc. 

 of urine in a test tube ; if turbidity appears add a drop or two of 

 strong acetic acid; if turbidity disappears it was due to phosphates, 

 if not to albumin, b. Put 2 or 3 cc. of strong nitric acid in a test 

 tube, then add urine, allowing it to run gently down the'iside of 

 the slanted test tube ; if albumin is present a ring of coagulum will 

 form between the acid and the urine. 



3. CHEMICAL TESTS FOR PROTEINS: Xantkoproteic Reaction. 

 Dilute some of the 10 per cent albumin till it is about 2 per cent; 

 place a small quantity in a test tube. Add a few drops of nitric 

 acid. What occurs? Boil. What occurs as to color and other 

 changes? Cool the solution and add ammonia until the acid is 

 neutralized. Note color produced. (This is the essential feature 

 of this reaction.) Try in the same way a weak solution of gelatin 

 (albuminoid) ; does it coagulate? Does it give the xanthoproteic 

 color ? 



4. ACTION OF ENYZMES ON PROTEINS. Thin pieces of boiled 

 white of egg were placed in artificial gastric juice, made by add- 

 ing pepsin to a 0.2 per cent solution of hydrochloric acid and 

 allowed to stand 24 hrs. Some of the digested albumin was placed 

 in one dialyzer and some fresh, undiluted albumin in another. Test 

 the water below each membrane for albumin. 



IV. ENZYMES (Organic Ferments). 



1. Chemical substances probably allied to proteins though they 

 have never been completely isolated. They are formed by animal 

 or plant protoplasm and act as catalyzers in many chemical re- 

 actions within living things. 



2. They are classified, according to what they do, as : 

 Amylo-lytic or Starch Splitting (Diastase, Ptyalian, etc.). 

 Lipo-lytic or Fat Splitting (Lipase, Steapsin, etc.). 

 Proteo-lytic or Protein Splitting (Pepsin, Tripsin, etc.). 

 Sugar Splitting (Maltase, Invertase, Lactase). 

 Alcohol forming (Zymase). 



Coagulating (Thrombin, Rennin). 

 Oxidizing (Oxidase, etc.) 



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