GENERAL BIOLOGY 



4. FERMENT ACTION: ENZYMES. 



a. Salivary diastase (ptyalin). Collect a few cc. of saliva in 

 a test tube ; dilute with about five volumes of water and filter into 

 two test tubes ; boil one of the tubes and leave the other unboiled. 

 Add to each tube an equal volume of dilute starch paste and place 

 tubes in incubator warmed to 40 C. for fifteen minutes. Then 

 divide the substance in each tube into two portions and test one 

 of each of these for starch (iodine) and the other for sugar 

 (Benedict's). What effect does ptyalin have on starch? What 

 effect does boiling have on ptyalin ? 



II. LIPINS (Oils, Fats, Yolk. etc.). 



1. OILS AND FATS, (i) Note physical properties, differences 

 in melting point, etc., of three fats olive oil, butter, and tallow. 

 Test solubilities of these fats in water, alcohol, chloroform, ether. 

 (2) Shake a few drops of olive oil with water in a test tube. What 

 happens ? Set tube aside for a few minutes. What happens ? Shake 

 up a few drops of the oil with one percent sodium carbonate in- 

 stead of water, examine with microscope, and note difference in 

 results. (This is an emulsion.) (3) Rub a thin film of butter on 

 a slide, and put on a drop of the dye known as Sudan III. Ob- 

 serve under microscope what occurs. 



Stain thin sections of Castor bean and of Lima bean with Sudan 



III. Is oil present in both? 



2. CHEMICAL TESTS FOR FATS. The reaction with ether and 

 with fat stains are two well-known tests for fats. 



III. PROTEINS (Albumins, Peptones, Albuminoids, etc.). 



Use white of egg as type of protein. 



1. Carefully pour white of egg into a dish. This is approxi- 

 mately a 12 per cent solution of a protein (albumin) in water. 

 Notice its consistency. Test its reaction with litmus paper; is it 

 acid, alkaline, or neutral? A 10 per cent solution of this white 

 of egg has been made by shaking it up with 9 times its volume of 

 distilled water and filtering. 



2. COAGULATION, (i) Coagulation by heat. Have a water 

 bath with water at the boiling temperature. Put some of the un- 

 diluted albumin in a test tube and place in the water bath. Does 

 it coagulate? Try a little of the 10 per cent solution in the same 

 way. Does it coagulate? What is the effect of dilution on coagula- 



